power/index
target/index
timers/index
+ spi/index
watchdog/index
virtual/index
input/index
+++ /dev/null
-spi_butterfly - parport-to-butterfly adapter driver
-===================================================
-
-This is a hardware and software project that includes building and using
-a parallel port adapter cable, together with an "AVR Butterfly" to run
-firmware for user interfacing and/or sensors. A Butterfly is a $US20
-battery powered card with an AVR microcontroller and lots of goodies:
-sensors, LCD, flash, toggle stick, and more. You can use AVR-GCC to
-develop firmware for this, and flash it using this adapter cable.
-
-You can make this adapter from an old printer cable and solder things
-directly to the Butterfly. Or (if you have the parts and skills) you
-can come up with something fancier, providing ciruit protection to the
-Butterfly and the printer port, or with a better power supply than two
-signal pins from the printer port. Or for that matter, you can use
-similar cables to talk to many AVR boards, even a breadboard.
-
-This is more powerful than "ISP programming" cables since it lets kernel
-SPI protocol drivers interact with the AVR, and could even let the AVR
-issue interrupts to them. Later, your protocol driver should work
-easily with a "real SPI controller", instead of this bitbanger.
-
-
-The first cable connections will hook Linux up to one SPI bus, with the
-AVR and a DataFlash chip; and to the AVR reset line. This is all you
-need to reflash the firmware, and the pins are the standard Atmel "ISP"
-connector pins (used also on non-Butterfly AVR boards). On the parport
-side this is like "sp12" programming cables.
-
- Signal Butterfly Parport (DB-25)
- ------ --------- ---------------
- SCK = J403.PB1/SCK = pin 2/D0
- RESET = J403.nRST = pin 3/D1
- VCC = J403.VCC_EXT = pin 8/D6
- MOSI = J403.PB2/MOSI = pin 9/D7
- MISO = J403.PB3/MISO = pin 11/S7,nBUSY
- GND = J403.GND = pin 23/GND
-
-Then to let Linux master that bus to talk to the DataFlash chip, you must
-(a) flash new firmware that disables SPI (set PRR.2, and disable pullups
-by clearing PORTB.[0-3]); (b) configure the mtd_dataflash driver; and
-(c) cable in the chipselect.
-
- Signal Butterfly Parport (DB-25)
- ------ --------- ---------------
- VCC = J400.VCC_EXT = pin 7/D5
- SELECT = J400.PB0/nSS = pin 17/C3,nSELECT
- GND = J400.GND = pin 24/GND
-
-Or you could flash firmware making the AVR into an SPI slave (keeping the
-DataFlash in reset) and tweak the spi_butterfly driver to make it bind to
-the driver for your custom SPI-based protocol.
-
-The "USI" controller, using J405, can also be used for a second SPI bus.
-That would let you talk to the AVR using custom SPI-with-USI firmware,
-while letting either Linux or the AVR use the DataFlash. There are plenty
-of spare parport pins to wire this one up, such as:
-
- Signal Butterfly Parport (DB-25)
- ------ --------- ---------------
- SCK = J403.PE4/USCK = pin 5/D3
- MOSI = J403.PE5/DI = pin 6/D4
- MISO = J403.PE6/DO = pin 12/S5,nPAPEROUT
- GND = J403.GND = pin 22/GND
-
- IRQ = J402.PF4 = pin 10/S6,ACK
- GND = J402.GND(P2) = pin 25/GND
-
--- /dev/null
+===================================================
+spi_butterfly - parport-to-butterfly adapter driver
+===================================================
+
+This is a hardware and software project that includes building and using
+a parallel port adapter cable, together with an "AVR Butterfly" to run
+firmware for user interfacing and/or sensors. A Butterfly is a $US20
+battery powered card with an AVR microcontroller and lots of goodies:
+sensors, LCD, flash, toggle stick, and more. You can use AVR-GCC to
+develop firmware for this, and flash it using this adapter cable.
+
+You can make this adapter from an old printer cable and solder things
+directly to the Butterfly. Or (if you have the parts and skills) you
+can come up with something fancier, providing ciruit protection to the
+Butterfly and the printer port, or with a better power supply than two
+signal pins from the printer port. Or for that matter, you can use
+similar cables to talk to many AVR boards, even a breadboard.
+
+This is more powerful than "ISP programming" cables since it lets kernel
+SPI protocol drivers interact with the AVR, and could even let the AVR
+issue interrupts to them. Later, your protocol driver should work
+easily with a "real SPI controller", instead of this bitbanger.
+
+
+The first cable connections will hook Linux up to one SPI bus, with the
+AVR and a DataFlash chip; and to the AVR reset line. This is all you
+need to reflash the firmware, and the pins are the standard Atmel "ISP"
+connector pins (used also on non-Butterfly AVR boards). On the parport
+side this is like "sp12" programming cables.
+
+ ====== ============= ===================
+ Signal Butterfly Parport (DB-25)
+ ====== ============= ===================
+ SCK J403.PB1/SCK pin 2/D0
+ RESET J403.nRST pin 3/D1
+ VCC J403.VCC_EXT pin 8/D6
+ MOSI J403.PB2/MOSI pin 9/D7
+ MISO J403.PB3/MISO pin 11/S7,nBUSY
+ GND J403.GND pin 23/GND
+ ====== ============= ===================
+
+Then to let Linux master that bus to talk to the DataFlash chip, you must
+(a) flash new firmware that disables SPI (set PRR.2, and disable pullups
+by clearing PORTB.[0-3]); (b) configure the mtd_dataflash driver; and
+(c) cable in the chipselect.
+
+ ====== ============ ===================
+ Signal Butterfly Parport (DB-25)
+ ====== ============ ===================
+ VCC J400.VCC_EXT pin 7/D5
+ SELECT J400.PB0/nSS pin 17/C3,nSELECT
+ GND J400.GND pin 24/GND
+ ====== ============ ===================
+
+Or you could flash firmware making the AVR into an SPI slave (keeping the
+DataFlash in reset) and tweak the spi_butterfly driver to make it bind to
+the driver for your custom SPI-based protocol.
+
+The "USI" controller, using J405, can also be used for a second SPI bus.
+That would let you talk to the AVR using custom SPI-with-USI firmware,
+while letting either Linux or the AVR use the DataFlash. There are plenty
+of spare parport pins to wire this one up, such as:
+
+ ====== ============= ===================
+ Signal Butterfly Parport (DB-25)
+ ====== ============= ===================
+ SCK J403.PE4/USCK pin 5/D3
+ MOSI J403.PE5/DI pin 6/D4
+ MISO J403.PE6/DO pin 12/S5,nPAPEROUT
+ GND J403.GND pin 22/GND
+
+ IRQ J402.PF4 pin 10/S6,ACK
+ GND J402.GND(P2) pin 25/GND
+ ====== ============= ===================
--- /dev/null
+.. SPDX-License-Identifier: GPL-2.0
+
+=================================
+Serial Peripheral Interface (SPI)
+=================================
+
+.. toctree::
+ :maxdepth: 1
+
+ spi-summary
+ spidev
+ butterfly
+ pxa2xx
+ spi-lm70llp
+ spi-sc18is602
+
+.. only:: subproject and html
+
+ Indices
+ =======
+
+ * :ref:`genindex`
+++ /dev/null
-PXA2xx SPI on SSP driver HOWTO
-===================================================
-This a mini howto on the pxa2xx_spi driver. The driver turns a PXA2xx
-synchronous serial port into a SPI master controller
-(see Documentation/spi/spi-summary). The driver has the following features
-
-- Support for any PXA2xx SSP
-- SSP PIO and SSP DMA data transfers.
-- External and Internal (SSPFRM) chip selects.
-- Per slave device (chip) configuration.
-- Full suspend, freeze, resume support.
-
-The driver is built around a "spi_message" fifo serviced by workqueue and a
-tasklet. The workqueue, "pump_messages", drives message fifo and the tasklet
-(pump_transfer) is responsible for queuing SPI transactions and setting up and
-launching the dma/interrupt driven transfers.
-
-Declaring PXA2xx Master Controllers
------------------------------------
-Typically a SPI master is defined in the arch/.../mach-*/board-*.c as a
-"platform device". The master configuration is passed to the driver via a table
-found in include/linux/spi/pxa2xx_spi.h:
-
-struct pxa2xx_spi_controller {
- u16 num_chipselect;
- u8 enable_dma;
-};
-
-The "pxa2xx_spi_controller.num_chipselect" field is used to determine the number of
-slave device (chips) attached to this SPI master.
-
-The "pxa2xx_spi_controller.enable_dma" field informs the driver that SSP DMA should
-be used. This caused the driver to acquire two DMA channels: rx_channel and
-tx_channel. The rx_channel has a higher DMA service priority the tx_channel.
-See the "PXA2xx Developer Manual" section "DMA Controller".
-
-NSSP MASTER SAMPLE
-------------------
-Below is a sample configuration using the PXA255 NSSP.
-
-static struct resource pxa_spi_nssp_resources[] = {
- [0] = {
- .start = __PREG(SSCR0_P(2)), /* Start address of NSSP */
- .end = __PREG(SSCR0_P(2)) + 0x2c, /* Range of registers */
- .flags = IORESOURCE_MEM,
- },
- [1] = {
- .start = IRQ_NSSP, /* NSSP IRQ */
- .end = IRQ_NSSP,
- .flags = IORESOURCE_IRQ,
- },
-};
-
-static struct pxa2xx_spi_controller pxa_nssp_master_info = {
- .num_chipselect = 1, /* Matches the number of chips attached to NSSP */
- .enable_dma = 1, /* Enables NSSP DMA */
-};
-
-static struct platform_device pxa_spi_nssp = {
- .name = "pxa2xx-spi", /* MUST BE THIS VALUE, so device match driver */
- .id = 2, /* Bus number, MUST MATCH SSP number 1..n */
- .resource = pxa_spi_nssp_resources,
- .num_resources = ARRAY_SIZE(pxa_spi_nssp_resources),
- .dev = {
- .platform_data = &pxa_nssp_master_info, /* Passed to driver */
- },
-};
-
-static struct platform_device *devices[] __initdata = {
- &pxa_spi_nssp,
-};
-
-static void __init board_init(void)
-{
- (void)platform_add_device(devices, ARRAY_SIZE(devices));
-}
-
-Declaring Slave Devices
------------------------
-Typically each SPI slave (chip) is defined in the arch/.../mach-*/board-*.c
-using the "spi_board_info" structure found in "linux/spi/spi.h". See
-"Documentation/spi/spi-summary" for additional information.
-
-Each slave device attached to the PXA must provide slave specific configuration
-information via the structure "pxa2xx_spi_chip" found in
-"include/linux/spi/pxa2xx_spi.h". The pxa2xx_spi master controller driver
-will uses the configuration whenever the driver communicates with the slave
-device. All fields are optional.
-
-struct pxa2xx_spi_chip {
- u8 tx_threshold;
- u8 rx_threshold;
- u8 dma_burst_size;
- u32 timeout;
- u8 enable_loopback;
- void (*cs_control)(u32 command);
-};
-
-The "pxa2xx_spi_chip.tx_threshold" and "pxa2xx_spi_chip.rx_threshold" fields are
-used to configure the SSP hardware fifo. These fields are critical to the
-performance of pxa2xx_spi driver and misconfiguration will result in rx
-fifo overruns (especially in PIO mode transfers). Good default values are
-
- .tx_threshold = 8,
- .rx_threshold = 8,
-
-The range is 1 to 16 where zero indicates "use default".
-
-The "pxa2xx_spi_chip.dma_burst_size" field is used to configure PXA2xx DMA
-engine and is related the "spi_device.bits_per_word" field. Read and understand
-the PXA2xx "Developer Manual" sections on the DMA controller and SSP Controllers
-to determine the correct value. An SSP configured for byte-wide transfers would
-use a value of 8. The driver will determine a reasonable default if
-dma_burst_size == 0.
-
-The "pxa2xx_spi_chip.timeout" fields is used to efficiently handle
-trailing bytes in the SSP receiver fifo. The correct value for this field is
-dependent on the SPI bus speed ("spi_board_info.max_speed_hz") and the specific
-slave device. Please note that the PXA2xx SSP 1 does not support trailing byte
-timeouts and must busy-wait any trailing bytes.
-
-The "pxa2xx_spi_chip.enable_loopback" field is used to place the SSP porting
-into internal loopback mode. In this mode the SSP controller internally
-connects the SSPTX pin to the SSPRX pin. This is useful for initial setup
-testing.
-
-The "pxa2xx_spi_chip.cs_control" field is used to point to a board specific
-function for asserting/deasserting a slave device chip select. If the field is
-NULL, the pxa2xx_spi master controller driver assumes that the SSP port is
-configured to use SSPFRM instead.
-
-NOTE: the SPI driver cannot control the chip select if SSPFRM is used, so the
-chipselect is dropped after each spi_transfer. Most devices need chip select
-asserted around the complete message. Use SSPFRM as a GPIO (through cs_control)
-to accommodate these chips.
-
-
-NSSP SLAVE SAMPLE
------------------
-The pxa2xx_spi_chip structure is passed to the pxa2xx_spi driver in the
-"spi_board_info.controller_data" field. Below is a sample configuration using
-the PXA255 NSSP.
-
-/* Chip Select control for the CS8415A SPI slave device */
-static void cs8415a_cs_control(u32 command)
-{
- if (command & PXA2XX_CS_ASSERT)
- GPCR(2) = GPIO_bit(2);
- else
- GPSR(2) = GPIO_bit(2);
-}
-
-/* Chip Select control for the CS8405A SPI slave device */
-static void cs8405a_cs_control(u32 command)
-{
- if (command & PXA2XX_CS_ASSERT)
- GPCR(3) = GPIO_bit(3);
- else
- GPSR(3) = GPIO_bit(3);
-}
-
-static struct pxa2xx_spi_chip cs8415a_chip_info = {
- .tx_threshold = 8, /* SSP hardward FIFO threshold */
- .rx_threshold = 8, /* SSP hardward FIFO threshold */
- .dma_burst_size = 8, /* Byte wide transfers used so 8 byte bursts */
- .timeout = 235, /* See Intel documentation */
- .cs_control = cs8415a_cs_control, /* Use external chip select */
-};
-
-static struct pxa2xx_spi_chip cs8405a_chip_info = {
- .tx_threshold = 8, /* SSP hardward FIFO threshold */
- .rx_threshold = 8, /* SSP hardward FIFO threshold */
- .dma_burst_size = 8, /* Byte wide transfers used so 8 byte bursts */
- .timeout = 235, /* See Intel documentation */
- .cs_control = cs8405a_cs_control, /* Use external chip select */
-};
-
-static struct spi_board_info streetracer_spi_board_info[] __initdata = {
- {
- .modalias = "cs8415a", /* Name of spi_driver for this device */
- .max_speed_hz = 3686400, /* Run SSP as fast a possbile */
- .bus_num = 2, /* Framework bus number */
- .chip_select = 0, /* Framework chip select */
- .platform_data = NULL; /* No spi_driver specific config */
- .controller_data = &cs8415a_chip_info, /* Master chip config */
- .irq = STREETRACER_APCI_IRQ, /* Slave device interrupt */
- },
- {
- .modalias = "cs8405a", /* Name of spi_driver for this device */
- .max_speed_hz = 3686400, /* Run SSP as fast a possbile */
- .bus_num = 2, /* Framework bus number */
- .chip_select = 1, /* Framework chip select */
- .controller_data = &cs8405a_chip_info, /* Master chip config */
- .irq = STREETRACER_APCI_IRQ, /* Slave device interrupt */
- },
-};
-
-static void __init streetracer_init(void)
-{
- spi_register_board_info(streetracer_spi_board_info,
- ARRAY_SIZE(streetracer_spi_board_info));
-}
-
-
-DMA and PIO I/O Support
------------------------
-The pxa2xx_spi driver supports both DMA and interrupt driven PIO message
-transfers. The driver defaults to PIO mode and DMA transfers must be enabled
-by setting the "enable_dma" flag in the "pxa2xx_spi_controller" structure. The DMA
-mode supports both coherent and stream based DMA mappings.
-
-The following logic is used to determine the type of I/O to be used on
-a per "spi_transfer" basis:
-
-if !enable_dma then
- always use PIO transfers
-
-if spi_message.len > 8191 then
- print "rate limited" warning
- use PIO transfers
-
-if spi_message.is_dma_mapped and rx_dma_buf != 0 and tx_dma_buf != 0 then
- use coherent DMA mode
-
-if rx_buf and tx_buf are aligned on 8 byte boundary then
- use streaming DMA mode
-
-otherwise
- use PIO transfer
-
-THANKS TO
----------
-
-David Brownell and others for mentoring the development of this driver.
-
--- /dev/null
+==============================
+PXA2xx SPI on SSP driver HOWTO
+==============================
+
+This a mini howto on the pxa2xx_spi driver. The driver turns a PXA2xx
+synchronous serial port into a SPI master controller
+(see Documentation/spi/spi-summary.rst). The driver has the following features
+
+- Support for any PXA2xx SSP
+- SSP PIO and SSP DMA data transfers.
+- External and Internal (SSPFRM) chip selects.
+- Per slave device (chip) configuration.
+- Full suspend, freeze, resume support.
+
+The driver is built around a "spi_message" fifo serviced by workqueue and a
+tasklet. The workqueue, "pump_messages", drives message fifo and the tasklet
+(pump_transfer) is responsible for queuing SPI transactions and setting up and
+launching the dma/interrupt driven transfers.
+
+Declaring PXA2xx Master Controllers
+-----------------------------------
+Typically a SPI master is defined in the arch/.../mach-*/board-*.c as a
+"platform device". The master configuration is passed to the driver via a table
+found in include/linux/spi/pxa2xx_spi.h::
+
+ struct pxa2xx_spi_controller {
+ u16 num_chipselect;
+ u8 enable_dma;
+ };
+
+The "pxa2xx_spi_controller.num_chipselect" field is used to determine the number of
+slave device (chips) attached to this SPI master.
+
+The "pxa2xx_spi_controller.enable_dma" field informs the driver that SSP DMA should
+be used. This caused the driver to acquire two DMA channels: rx_channel and
+tx_channel. The rx_channel has a higher DMA service priority the tx_channel.
+See the "PXA2xx Developer Manual" section "DMA Controller".
+
+NSSP MASTER SAMPLE
+------------------
+Below is a sample configuration using the PXA255 NSSP::
+
+ static struct resource pxa_spi_nssp_resources[] = {
+ [0] = {
+ .start = __PREG(SSCR0_P(2)), /* Start address of NSSP */
+ .end = __PREG(SSCR0_P(2)) + 0x2c, /* Range of registers */
+ .flags = IORESOURCE_MEM,
+ },
+ [1] = {
+ .start = IRQ_NSSP, /* NSSP IRQ */
+ .end = IRQ_NSSP,
+ .flags = IORESOURCE_IRQ,
+ },
+ };
+
+ static struct pxa2xx_spi_controller pxa_nssp_master_info = {
+ .num_chipselect = 1, /* Matches the number of chips attached to NSSP */
+ .enable_dma = 1, /* Enables NSSP DMA */
+ };
+
+ static struct platform_device pxa_spi_nssp = {
+ .name = "pxa2xx-spi", /* MUST BE THIS VALUE, so device match driver */
+ .id = 2, /* Bus number, MUST MATCH SSP number 1..n */
+ .resource = pxa_spi_nssp_resources,
+ .num_resources = ARRAY_SIZE(pxa_spi_nssp_resources),
+ .dev = {
+ .platform_data = &pxa_nssp_master_info, /* Passed to driver */
+ },
+ };
+
+ static struct platform_device *devices[] __initdata = {
+ &pxa_spi_nssp,
+ };
+
+ static void __init board_init(void)
+ {
+ (void)platform_add_device(devices, ARRAY_SIZE(devices));
+ }
+
+Declaring Slave Devices
+-----------------------
+Typically each SPI slave (chip) is defined in the arch/.../mach-*/board-*.c
+using the "spi_board_info" structure found in "linux/spi/spi.h". See
+"Documentation/spi/spi-summary.rst" for additional information.
+
+Each slave device attached to the PXA must provide slave specific configuration
+information via the structure "pxa2xx_spi_chip" found in
+"include/linux/spi/pxa2xx_spi.h". The pxa2xx_spi master controller driver
+will uses the configuration whenever the driver communicates with the slave
+device. All fields are optional.
+
+::
+
+ struct pxa2xx_spi_chip {
+ u8 tx_threshold;
+ u8 rx_threshold;
+ u8 dma_burst_size;
+ u32 timeout;
+ u8 enable_loopback;
+ void (*cs_control)(u32 command);
+ };
+
+The "pxa2xx_spi_chip.tx_threshold" and "pxa2xx_spi_chip.rx_threshold" fields are
+used to configure the SSP hardware fifo. These fields are critical to the
+performance of pxa2xx_spi driver and misconfiguration will result in rx
+fifo overruns (especially in PIO mode transfers). Good default values are::
+
+ .tx_threshold = 8,
+ .rx_threshold = 8,
+
+The range is 1 to 16 where zero indicates "use default".
+
+The "pxa2xx_spi_chip.dma_burst_size" field is used to configure PXA2xx DMA
+engine and is related the "spi_device.bits_per_word" field. Read and understand
+the PXA2xx "Developer Manual" sections on the DMA controller and SSP Controllers
+to determine the correct value. An SSP configured for byte-wide transfers would
+use a value of 8. The driver will determine a reasonable default if
+dma_burst_size == 0.
+
+The "pxa2xx_spi_chip.timeout" fields is used to efficiently handle
+trailing bytes in the SSP receiver fifo. The correct value for this field is
+dependent on the SPI bus speed ("spi_board_info.max_speed_hz") and the specific
+slave device. Please note that the PXA2xx SSP 1 does not support trailing byte
+timeouts and must busy-wait any trailing bytes.
+
+The "pxa2xx_spi_chip.enable_loopback" field is used to place the SSP porting
+into internal loopback mode. In this mode the SSP controller internally
+connects the SSPTX pin to the SSPRX pin. This is useful for initial setup
+testing.
+
+The "pxa2xx_spi_chip.cs_control" field is used to point to a board specific
+function for asserting/deasserting a slave device chip select. If the field is
+NULL, the pxa2xx_spi master controller driver assumes that the SSP port is
+configured to use SSPFRM instead.
+
+NOTE: the SPI driver cannot control the chip select if SSPFRM is used, so the
+chipselect is dropped after each spi_transfer. Most devices need chip select
+asserted around the complete message. Use SSPFRM as a GPIO (through cs_control)
+to accommodate these chips.
+
+
+NSSP SLAVE SAMPLE
+-----------------
+The pxa2xx_spi_chip structure is passed to the pxa2xx_spi driver in the
+"spi_board_info.controller_data" field. Below is a sample configuration using
+the PXA255 NSSP.
+
+::
+
+ /* Chip Select control for the CS8415A SPI slave device */
+ static void cs8415a_cs_control(u32 command)
+ {
+ if (command & PXA2XX_CS_ASSERT)
+ GPCR(2) = GPIO_bit(2);
+ else
+ GPSR(2) = GPIO_bit(2);
+ }
+
+ /* Chip Select control for the CS8405A SPI slave device */
+ static void cs8405a_cs_control(u32 command)
+ {
+ if (command & PXA2XX_CS_ASSERT)
+ GPCR(3) = GPIO_bit(3);
+ else
+ GPSR(3) = GPIO_bit(3);
+ }
+
+ static struct pxa2xx_spi_chip cs8415a_chip_info = {
+ .tx_threshold = 8, /* SSP hardward FIFO threshold */
+ .rx_threshold = 8, /* SSP hardward FIFO threshold */
+ .dma_burst_size = 8, /* Byte wide transfers used so 8 byte bursts */
+ .timeout = 235, /* See Intel documentation */
+ .cs_control = cs8415a_cs_control, /* Use external chip select */
+ };
+
+ static struct pxa2xx_spi_chip cs8405a_chip_info = {
+ .tx_threshold = 8, /* SSP hardward FIFO threshold */
+ .rx_threshold = 8, /* SSP hardward FIFO threshold */
+ .dma_burst_size = 8, /* Byte wide transfers used so 8 byte bursts */
+ .timeout = 235, /* See Intel documentation */
+ .cs_control = cs8405a_cs_control, /* Use external chip select */
+ };
+
+ static struct spi_board_info streetracer_spi_board_info[] __initdata = {
+ {
+ .modalias = "cs8415a", /* Name of spi_driver for this device */
+ .max_speed_hz = 3686400, /* Run SSP as fast a possbile */
+ .bus_num = 2, /* Framework bus number */
+ .chip_select = 0, /* Framework chip select */
+ .platform_data = NULL; /* No spi_driver specific config */
+ .controller_data = &cs8415a_chip_info, /* Master chip config */
+ .irq = STREETRACER_APCI_IRQ, /* Slave device interrupt */
+ },
+ {
+ .modalias = "cs8405a", /* Name of spi_driver for this device */
+ .max_speed_hz = 3686400, /* Run SSP as fast a possbile */
+ .bus_num = 2, /* Framework bus number */
+ .chip_select = 1, /* Framework chip select */
+ .controller_data = &cs8405a_chip_info, /* Master chip config */
+ .irq = STREETRACER_APCI_IRQ, /* Slave device interrupt */
+ },
+ };
+
+ static void __init streetracer_init(void)
+ {
+ spi_register_board_info(streetracer_spi_board_info,
+ ARRAY_SIZE(streetracer_spi_board_info));
+ }
+
+
+DMA and PIO I/O Support
+-----------------------
+The pxa2xx_spi driver supports both DMA and interrupt driven PIO message
+transfers. The driver defaults to PIO mode and DMA transfers must be enabled
+by setting the "enable_dma" flag in the "pxa2xx_spi_controller" structure. The DMA
+mode supports both coherent and stream based DMA mappings.
+
+The following logic is used to determine the type of I/O to be used on
+a per "spi_transfer" basis::
+
+ if !enable_dma then
+ always use PIO transfers
+
+ if spi_message.len > 8191 then
+ print "rate limited" warning
+ use PIO transfers
+
+ if spi_message.is_dma_mapped and rx_dma_buf != 0 and tx_dma_buf != 0 then
+ use coherent DMA mode
+
+ if rx_buf and tx_buf are aligned on 8 byte boundary then
+ use streaming DMA mode
+
+ otherwise
+ use PIO transfer
+
+THANKS TO
+---------
+
+David Brownell and others for mentoring the development of this driver.
+++ /dev/null
-spi_lm70llp : LM70-LLP parport-to-SPI adapter
-==============================================
-
-Supported board/chip:
- * National Semiconductor LM70 LLP evaluation board
- Datasheet: http://www.national.com/pf/LM/LM70.html
-
-Author:
- Kaiwan N Billimoria <kaiwan@designergraphix.com>
-
-Description
------------
-This driver provides glue code connecting a National Semiconductor LM70 LLP
-temperature sensor evaluation board to the kernel's SPI core subsystem.
-
-This is a SPI master controller driver. It can be used in conjunction with
-(layered under) the LM70 logical driver (a "SPI protocol driver").
-In effect, this driver turns the parallel port interface on the eval board
-into a SPI bus with a single device, which will be driven by the generic
-LM70 driver (drivers/hwmon/lm70.c).
-
-
-Hardware Interfacing
---------------------
-The schematic for this particular board (the LM70EVAL-LLP) is
-available (on page 4) here:
-
- http://www.national.com/appinfo/tempsensors/files/LM70LLPEVALmanual.pdf
-
-The hardware interfacing on the LM70 LLP eval board is as follows:
-
- Parallel LM70 LLP
- Port Direction JP2 Header
- ----------- --------- ----------------
- D0 2 - -
- D1 3 --> V+ 5
- D2 4 --> V+ 5
- D3 5 --> V+ 5
- D4 6 --> V+ 5
- D5 7 --> nCS 8
- D6 8 --> SCLK 3
- D7 9 --> SI/O 5
- GND 25 - GND 7
- Select 13 <-- SI/O 1
- ----------- --------- ----------------
-
-Note that since the LM70 uses a "3-wire" variant of SPI, the SI/SO pin
-is connected to both pin D7 (as Master Out) and Select (as Master In)
-using an arrangement that lets either the parport or the LM70 pull the
-pin low. This can't be shared with true SPI devices, but other 3-wire
-devices might share the same SI/SO pin.
-
-The bitbanger routine in this driver (lm70_txrx) is called back from
-the bound "hwmon/lm70" protocol driver through its sysfs hook, using a
-spi_write_then_read() call. It performs Mode 0 (SPI/Microwire) bitbanging.
-The lm70 driver then inteprets the resulting digital temperature value
-and exports it through sysfs.
-
-A "gotcha": National Semiconductor's LM70 LLP eval board circuit schematic
-shows that the SI/O line from the LM70 chip is connected to the base of a
-transistor Q1 (and also a pullup, and a zener diode to D7); while the
-collector is tied to VCC.
-
-Interpreting this circuit, when the LM70 SI/O line is High (or tristate
-and not grounded by the host via D7), the transistor conducts and switches
-the collector to zero, which is reflected on pin 13 of the DB25 parport
-connector. When SI/O is Low (driven by the LM70 or the host) on the other
-hand, the transistor is cut off and the voltage tied to it's collector is
-reflected on pin 13 as a High level.
-
-So: the getmiso inline routine in this driver takes this fact into account,
-inverting the value read at pin 13.
-
-
-Thanks to
----------
-o David Brownell for mentoring the SPI-side driver development.
-o Dr.Craig Hollabaugh for the (early) "manual" bitbanging driver version.
-o Nadir Billimoria for help interpreting the circuit schematic.
--- /dev/null
+==============================================
+spi_lm70llp : LM70-LLP parport-to-SPI adapter
+==============================================
+
+Supported board/chip:
+
+ * National Semiconductor LM70 LLP evaluation board
+
+ Datasheet: http://www.national.com/pf/LM/LM70.html
+
+Author:
+ Kaiwan N Billimoria <kaiwan@designergraphix.com>
+
+Description
+-----------
+This driver provides glue code connecting a National Semiconductor LM70 LLP
+temperature sensor evaluation board to the kernel's SPI core subsystem.
+
+This is a SPI master controller driver. It can be used in conjunction with
+(layered under) the LM70 logical driver (a "SPI protocol driver").
+In effect, this driver turns the parallel port interface on the eval board
+into a SPI bus with a single device, which will be driven by the generic
+LM70 driver (drivers/hwmon/lm70.c).
+
+
+Hardware Interfacing
+--------------------
+The schematic for this particular board (the LM70EVAL-LLP) is
+available (on page 4) here:
+
+ http://www.national.com/appinfo/tempsensors/files/LM70LLPEVALmanual.pdf
+
+The hardware interfacing on the LM70 LLP eval board is as follows:
+
+ ======== == ========= ==========
+ Parallel LM70 LLP
+ Port . Direction JP2 Header
+ ======== == ========= ==========
+ D0 2 - -
+ D1 3 --> V+ 5
+ D2 4 --> V+ 5
+ D3 5 --> V+ 5
+ D4 6 --> V+ 5
+ D5 7 --> nCS 8
+ D6 8 --> SCLK 3
+ D7 9 --> SI/O 5
+ GND 25 - GND 7
+ Select 13 <-- SI/O 1
+ ======== == ========= ==========
+
+Note that since the LM70 uses a "3-wire" variant of SPI, the SI/SO pin
+is connected to both pin D7 (as Master Out) and Select (as Master In)
+using an arrangement that lets either the parport or the LM70 pull the
+pin low. This can't be shared with true SPI devices, but other 3-wire
+devices might share the same SI/SO pin.
+
+The bitbanger routine in this driver (lm70_txrx) is called back from
+the bound "hwmon/lm70" protocol driver through its sysfs hook, using a
+spi_write_then_read() call. It performs Mode 0 (SPI/Microwire) bitbanging.
+The lm70 driver then inteprets the resulting digital temperature value
+and exports it through sysfs.
+
+A "gotcha": National Semiconductor's LM70 LLP eval board circuit schematic
+shows that the SI/O line from the LM70 chip is connected to the base of a
+transistor Q1 (and also a pullup, and a zener diode to D7); while the
+collector is tied to VCC.
+
+Interpreting this circuit, when the LM70 SI/O line is High (or tristate
+and not grounded by the host via D7), the transistor conducts and switches
+the collector to zero, which is reflected on pin 13 of the DB25 parport
+connector. When SI/O is Low (driven by the LM70 or the host) on the other
+hand, the transistor is cut off and the voltage tied to it's collector is
+reflected on pin 13 as a High level.
+
+So: the getmiso inline routine in this driver takes this fact into account,
+inverting the value read at pin 13.
+
+
+Thanks to
+---------
+
+- David Brownell for mentoring the SPI-side driver development.
+- Dr.Craig Hollabaugh for the (early) "manual" bitbanging driver version.
+- Nadir Billimoria for help interpreting the circuit schematic.
+++ /dev/null
-Kernel driver spi-sc18is602
-===========================
-
-Supported chips:
- * NXP SI18IS602/602B/603
- Datasheet: http://www.nxp.com/documents/data_sheet/SC18IS602_602B_603.pdf
-
-Author:
- Guenter Roeck <linux@roeck-us.net>
-
-
-Description
------------
-
-This driver provides connects a NXP SC18IS602/603 I2C-bus to SPI bridge to the
-kernel's SPI core subsystem.
-
-The driver does not probe for supported chips, since the SI18IS602/603 does not
-support Chip ID registers. You will have to instantiate the devices explicitly.
-Please see Documentation/i2c/instantiating-devices.rst for details.
-
-
-Usage Notes
------------
-
-This driver requires the I2C adapter driver to support raw I2C messages. I2C
-adapter drivers which can only handle the SMBus protocol are not supported.
-
-The maximum SPI message size supported by SC18IS602/603 is 200 bytes. Attempts
-to initiate longer transfers will fail with -EINVAL. EEPROM read operations and
-similar large accesses have to be split into multiple chunks of no more than
-200 bytes per SPI message (128 bytes of data per message is recommended). This
-means that programs such as "cp" or "od", which automatically use large block
-sizes to access a device, can not be used directly to read data from EEPROM.
-Programs such as dd, where the block size can be specified, should be used
-instead.
--- /dev/null
+===========================
+Kernel driver spi-sc18is602
+===========================
+
+Supported chips:
+
+ * NXP SI18IS602/602B/603
+
+ Datasheet: http://www.nxp.com/documents/data_sheet/SC18IS602_602B_603.pdf
+
+Author:
+ Guenter Roeck <linux@roeck-us.net>
+
+
+Description
+-----------
+
+This driver provides connects a NXP SC18IS602/603 I2C-bus to SPI bridge to the
+kernel's SPI core subsystem.
+
+The driver does not probe for supported chips, since the SI18IS602/603 does not
+support Chip ID registers. You will have to instantiate the devices explicitly.
+Please see Documentation/i2c/instantiating-devices.rst for details.
+
+
+Usage Notes
+-----------
+
+This driver requires the I2C adapter driver to support raw I2C messages. I2C
+adapter drivers which can only handle the SMBus protocol are not supported.
+
+The maximum SPI message size supported by SC18IS602/603 is 200 bytes. Attempts
+to initiate longer transfers will fail with -EINVAL. EEPROM read operations and
+similar large accesses have to be split into multiple chunks of no more than
+200 bytes per SPI message (128 bytes of data per message is recommended). This
+means that programs such as "cp" or "od", which automatically use large block
+sizes to access a device, can not be used directly to read data from EEPROM.
+Programs such as dd, where the block size can be specified, should be used
+instead.
+++ /dev/null
-Overview of Linux kernel SPI support
-====================================
-
-02-Feb-2012
-
-What is SPI?
-------------
-The "Serial Peripheral Interface" (SPI) is a synchronous four wire serial
-link used to connect microcontrollers to sensors, memory, and peripherals.
-It's a simple "de facto" standard, not complicated enough to acquire a
-standardization body. SPI uses a master/slave configuration.
-
-The three signal wires hold a clock (SCK, often on the order of 10 MHz),
-and parallel data lines with "Master Out, Slave In" (MOSI) or "Master In,
-Slave Out" (MISO) signals. (Other names are also used.) There are four
-clocking modes through which data is exchanged; mode-0 and mode-3 are most
-commonly used. Each clock cycle shifts data out and data in; the clock
-doesn't cycle except when there is a data bit to shift. Not all data bits
-are used though; not every protocol uses those full duplex capabilities.
-
-SPI masters use a fourth "chip select" line to activate a given SPI slave
-device, so those three signal wires may be connected to several chips
-in parallel. All SPI slaves support chipselects; they are usually active
-low signals, labeled nCSx for slave 'x' (e.g. nCS0). Some devices have
-other signals, often including an interrupt to the master.
-
-Unlike serial busses like USB or SMBus, even low level protocols for
-SPI slave functions are usually not interoperable between vendors
-(except for commodities like SPI memory chips).
-
- - SPI may be used for request/response style device protocols, as with
- touchscreen sensors and memory chips.
-
- - It may also be used to stream data in either direction (half duplex),
- or both of them at the same time (full duplex).
-
- - Some devices may use eight bit words. Others may use different word
- lengths, such as streams of 12-bit or 20-bit digital samples.
-
- - Words are usually sent with their most significant bit (MSB) first,
- but sometimes the least significant bit (LSB) goes first instead.
-
- - Sometimes SPI is used to daisy-chain devices, like shift registers.
-
-In the same way, SPI slaves will only rarely support any kind of automatic
-discovery/enumeration protocol. The tree of slave devices accessible from
-a given SPI master will normally be set up manually, with configuration
-tables.
-
-SPI is only one of the names used by such four-wire protocols, and
-most controllers have no problem handling "MicroWire" (think of it as
-half-duplex SPI, for request/response protocols), SSP ("Synchronous
-Serial Protocol"), PSP ("Programmable Serial Protocol"), and other
-related protocols.
-
-Some chips eliminate a signal line by combining MOSI and MISO, and
-limiting themselves to half-duplex at the hardware level. In fact
-some SPI chips have this signal mode as a strapping option. These
-can be accessed using the same programming interface as SPI, but of
-course they won't handle full duplex transfers. You may find such
-chips described as using "three wire" signaling: SCK, data, nCSx.
-(That data line is sometimes called MOMI or SISO.)
-
-Microcontrollers often support both master and slave sides of the SPI
-protocol. This document (and Linux) supports both the master and slave
-sides of SPI interactions.
-
-
-Who uses it? On what kinds of systems?
----------------------------------------
-Linux developers using SPI are probably writing device drivers for embedded
-systems boards. SPI is used to control external chips, and it is also a
-protocol supported by every MMC or SD memory card. (The older "DataFlash"
-cards, predating MMC cards but using the same connectors and card shape,
-support only SPI.) Some PC hardware uses SPI flash for BIOS code.
-
-SPI slave chips range from digital/analog converters used for analog
-sensors and codecs, to memory, to peripherals like USB controllers
-or Ethernet adapters; and more.
-
-Most systems using SPI will integrate a few devices on a mainboard.
-Some provide SPI links on expansion connectors; in cases where no
-dedicated SPI controller exists, GPIO pins can be used to create a
-low speed "bitbanging" adapter. Very few systems will "hotplug" an SPI
-controller; the reasons to use SPI focus on low cost and simple operation,
-and if dynamic reconfiguration is important, USB will often be a more
-appropriate low-pincount peripheral bus.
-
-Many microcontrollers that can run Linux integrate one or more I/O
-interfaces with SPI modes. Given SPI support, they could use MMC or SD
-cards without needing a special purpose MMC/SD/SDIO controller.
-
-
-I'm confused. What are these four SPI "clock modes"?
------------------------------------------------------
-It's easy to be confused here, and the vendor documentation you'll
-find isn't necessarily helpful. The four modes combine two mode bits:
-
- - CPOL indicates the initial clock polarity. CPOL=0 means the
- clock starts low, so the first (leading) edge is rising, and
- the second (trailing) edge is falling. CPOL=1 means the clock
- starts high, so the first (leading) edge is falling.
-
- - CPHA indicates the clock phase used to sample data; CPHA=0 says
- sample on the leading edge, CPHA=1 means the trailing edge.
-
- Since the signal needs to stablize before it's sampled, CPHA=0
- implies that its data is written half a clock before the first
- clock edge. The chipselect may have made it become available.
-
-Chip specs won't always say "uses SPI mode X" in as many words,
-but their timing diagrams will make the CPOL and CPHA modes clear.
-
-In the SPI mode number, CPOL is the high order bit and CPHA is the
-low order bit. So when a chip's timing diagram shows the clock
-starting low (CPOL=0) and data stabilized for sampling during the
-trailing clock edge (CPHA=1), that's SPI mode 1.
-
-Note that the clock mode is relevant as soon as the chipselect goes
-active. So the master must set the clock to inactive before selecting
-a slave, and the slave can tell the chosen polarity by sampling the
-clock level when its select line goes active. That's why many devices
-support for example both modes 0 and 3: they don't care about polarity,
-and always clock data in/out on rising clock edges.
-
-
-How do these driver programming interfaces work?
-------------------------------------------------
-The <linux/spi/spi.h> header file includes kerneldoc, as does the
-main source code, and you should certainly read that chapter of the
-kernel API document. This is just an overview, so you get the big
-picture before those details.
-
-SPI requests always go into I/O queues. Requests for a given SPI device
-are always executed in FIFO order, and complete asynchronously through
-completion callbacks. There are also some simple synchronous wrappers
-for those calls, including ones for common transaction types like writing
-a command and then reading its response.
-
-There are two types of SPI driver, here called:
-
- Controller drivers ... controllers may be built into System-On-Chip
- processors, and often support both Master and Slave roles.
- These drivers touch hardware registers and may use DMA.
- Or they can be PIO bitbangers, needing just GPIO pins.
-
- Protocol drivers ... these pass messages through the controller
- driver to communicate with a Slave or Master device on the
- other side of an SPI link.
-
-So for example one protocol driver might talk to the MTD layer to export
-data to filesystems stored on SPI flash like DataFlash; and others might
-control audio interfaces, present touchscreen sensors as input interfaces,
-or monitor temperature and voltage levels during industrial processing.
-And those might all be sharing the same controller driver.
-
-A "struct spi_device" encapsulates the controller-side interface between
-those two types of drivers.
-
-There is a minimal core of SPI programming interfaces, focussing on
-using the driver model to connect controller and protocol drivers using
-device tables provided by board specific initialization code. SPI
-shows up in sysfs in several locations:
-
- /sys/devices/.../CTLR ... physical node for a given SPI controller
-
- /sys/devices/.../CTLR/spiB.C ... spi_device on bus "B",
- chipselect C, accessed through CTLR.
-
- /sys/bus/spi/devices/spiB.C ... symlink to that physical
- .../CTLR/spiB.C device
-
- /sys/devices/.../CTLR/spiB.C/modalias ... identifies the driver
- that should be used with this device (for hotplug/coldplug)
-
- /sys/bus/spi/drivers/D ... driver for one or more spi*.* devices
-
- /sys/class/spi_master/spiB ... symlink (or actual device node) to
- a logical node which could hold class related state for the SPI
- master controller managing bus "B". All spiB.* devices share one
- physical SPI bus segment, with SCLK, MOSI, and MISO.
-
- /sys/devices/.../CTLR/slave ... virtual file for (un)registering the
- slave device for an SPI slave controller.
- Writing the driver name of an SPI slave handler to this file
- registers the slave device; writing "(null)" unregisters the slave
- device.
- Reading from this file shows the name of the slave device ("(null)"
- if not registered).
-
- /sys/class/spi_slave/spiB ... symlink (or actual device node) to
- a logical node which could hold class related state for the SPI
- slave controller on bus "B". When registered, a single spiB.*
- device is present here, possible sharing the physical SPI bus
- segment with other SPI slave devices.
-
-Note that the actual location of the controller's class state depends
-on whether you enabled CONFIG_SYSFS_DEPRECATED or not. At this time,
-the only class-specific state is the bus number ("B" in "spiB"), so
-those /sys/class entries are only useful to quickly identify busses.
-
-
-How does board-specific init code declare SPI devices?
-------------------------------------------------------
-Linux needs several kinds of information to properly configure SPI devices.
-That information is normally provided by board-specific code, even for
-chips that do support some of automated discovery/enumeration.
-
-DECLARE CONTROLLERS
-
-The first kind of information is a list of what SPI controllers exist.
-For System-on-Chip (SOC) based boards, these will usually be platform
-devices, and the controller may need some platform_data in order to
-operate properly. The "struct platform_device" will include resources
-like the physical address of the controller's first register and its IRQ.
-
-Platforms will often abstract the "register SPI controller" operation,
-maybe coupling it with code to initialize pin configurations, so that
-the arch/.../mach-*/board-*.c files for several boards can all share the
-same basic controller setup code. This is because most SOCs have several
-SPI-capable controllers, and only the ones actually usable on a given
-board should normally be set up and registered.
-
-So for example arch/.../mach-*/board-*.c files might have code like:
-
- #include <mach/spi.h> /* for mysoc_spi_data */
-
- /* if your mach-* infrastructure doesn't support kernels that can
- * run on multiple boards, pdata wouldn't benefit from "__init".
- */
- static struct mysoc_spi_data pdata __initdata = { ... };
-
- static __init board_init(void)
- {
- ...
- /* this board only uses SPI controller #2 */
- mysoc_register_spi(2, &pdata);
- ...
- }
-
-And SOC-specific utility code might look something like:
-
- #include <mach/spi.h>
-
- static struct platform_device spi2 = { ... };
-
- void mysoc_register_spi(unsigned n, struct mysoc_spi_data *pdata)
- {
- struct mysoc_spi_data *pdata2;
-
- pdata2 = kmalloc(sizeof *pdata2, GFP_KERNEL);
- *pdata2 = pdata;
- ...
- if (n == 2) {
- spi2->dev.platform_data = pdata2;
- register_platform_device(&spi2);
-
- /* also: set up pin modes so the spi2 signals are
- * visible on the relevant pins ... bootloaders on
- * production boards may already have done this, but
- * developer boards will often need Linux to do it.
- */
- }
- ...
- }
-
-Notice how the platform_data for boards may be different, even if the
-same SOC controller is used. For example, on one board SPI might use
-an external clock, where another derives the SPI clock from current
-settings of some master clock.
-
-
-DECLARE SLAVE DEVICES
-
-The second kind of information is a list of what SPI slave devices exist
-on the target board, often with some board-specific data needed for the
-driver to work correctly.
-
-Normally your arch/.../mach-*/board-*.c files would provide a small table
-listing the SPI devices on each board. (This would typically be only a
-small handful.) That might look like:
-
- static struct ads7846_platform_data ads_info = {
- .vref_delay_usecs = 100,
- .x_plate_ohms = 580,
- .y_plate_ohms = 410,
- };
-
- static struct spi_board_info spi_board_info[] __initdata = {
- {
- .modalias = "ads7846",
- .platform_data = &ads_info,
- .mode = SPI_MODE_0,
- .irq = GPIO_IRQ(31),
- .max_speed_hz = 120000 /* max sample rate at 3V */ * 16,
- .bus_num = 1,
- .chip_select = 0,
- },
- };
-
-Again, notice how board-specific information is provided; each chip may need
-several types. This example shows generic constraints like the fastest SPI
-clock to allow (a function of board voltage in this case) or how an IRQ pin
-is wired, plus chip-specific constraints like an important delay that's
-changed by the capacitance at one pin.
-
-(There's also "controller_data", information that may be useful to the
-controller driver. An example would be peripheral-specific DMA tuning
-data or chipselect callbacks. This is stored in spi_device later.)
-
-The board_info should provide enough information to let the system work
-without the chip's driver being loaded. The most troublesome aspect of
-that is likely the SPI_CS_HIGH bit in the spi_device.mode field, since
-sharing a bus with a device that interprets chipselect "backwards" is
-not possible until the infrastructure knows how to deselect it.
-
-Then your board initialization code would register that table with the SPI
-infrastructure, so that it's available later when the SPI master controller
-driver is registered:
-
- spi_register_board_info(spi_board_info, ARRAY_SIZE(spi_board_info));
-
-Like with other static board-specific setup, you won't unregister those.
-
-The widely used "card" style computers bundle memory, cpu, and little else
-onto a card that's maybe just thirty square centimeters. On such systems,
-your arch/.../mach-.../board-*.c file would primarily provide information
-about the devices on the mainboard into which such a card is plugged. That
-certainly includes SPI devices hooked up through the card connectors!
-
-
-NON-STATIC CONFIGURATIONS
-
-Developer boards often play by different rules than product boards, and one
-example is the potential need to hotplug SPI devices and/or controllers.
-
-For those cases you might need to use spi_busnum_to_master() to look
-up the spi bus master, and will likely need spi_new_device() to provide the
-board info based on the board that was hotplugged. Of course, you'd later
-call at least spi_unregister_device() when that board is removed.
-
-When Linux includes support for MMC/SD/SDIO/DataFlash cards through SPI, those
-configurations will also be dynamic. Fortunately, such devices all support
-basic device identification probes, so they should hotplug normally.
-
-
-How do I write an "SPI Protocol Driver"?
-----------------------------------------
-Most SPI drivers are currently kernel drivers, but there's also support
-for userspace drivers. Here we talk only about kernel drivers.
-
-SPI protocol drivers somewhat resemble platform device drivers:
-
- static struct spi_driver CHIP_driver = {
- .driver = {
- .name = "CHIP",
- .owner = THIS_MODULE,
- .pm = &CHIP_pm_ops,
- },
-
- .probe = CHIP_probe,
- .remove = CHIP_remove,
- };
-
-The driver core will automatically attempt to bind this driver to any SPI
-device whose board_info gave a modalias of "CHIP". Your probe() code
-might look like this unless you're creating a device which is managing
-a bus (appearing under /sys/class/spi_master).
-
- static int CHIP_probe(struct spi_device *spi)
- {
- struct CHIP *chip;
- struct CHIP_platform_data *pdata;
-
- /* assuming the driver requires board-specific data: */
- pdata = &spi->dev.platform_data;
- if (!pdata)
- return -ENODEV;
-
- /* get memory for driver's per-chip state */
- chip = kzalloc(sizeof *chip, GFP_KERNEL);
- if (!chip)
- return -ENOMEM;
- spi_set_drvdata(spi, chip);
-
- ... etc
- return 0;
- }
-
-As soon as it enters probe(), the driver may issue I/O requests to
-the SPI device using "struct spi_message". When remove() returns,
-or after probe() fails, the driver guarantees that it won't submit
-any more such messages.
-
- - An spi_message is a sequence of protocol operations, executed
- as one atomic sequence. SPI driver controls include:
-
- + when bidirectional reads and writes start ... by how its
- sequence of spi_transfer requests is arranged;
-
- + which I/O buffers are used ... each spi_transfer wraps a
- buffer for each transfer direction, supporting full duplex
- (two pointers, maybe the same one in both cases) and half
- duplex (one pointer is NULL) transfers;
-
- + optionally defining short delays after transfers ... using
- the spi_transfer.delay_usecs setting (this delay can be the
- only protocol effect, if the buffer length is zero);
-
- + whether the chipselect becomes inactive after a transfer and
- any delay ... by using the spi_transfer.cs_change flag;
-
- + hinting whether the next message is likely to go to this same
- device ... using the spi_transfer.cs_change flag on the last
- transfer in that atomic group, and potentially saving costs
- for chip deselect and select operations.
-
- - Follow standard kernel rules, and provide DMA-safe buffers in
- your messages. That way controller drivers using DMA aren't forced
- to make extra copies unless the hardware requires it (e.g. working
- around hardware errata that force the use of bounce buffering).
-
- If standard dma_map_single() handling of these buffers is inappropriate,
- you can use spi_message.is_dma_mapped to tell the controller driver
- that you've already provided the relevant DMA addresses.
-
- - The basic I/O primitive is spi_async(). Async requests may be
- issued in any context (irq handler, task, etc) and completion
- is reported using a callback provided with the message.
- After any detected error, the chip is deselected and processing
- of that spi_message is aborted.
-
- - There are also synchronous wrappers like spi_sync(), and wrappers
- like spi_read(), spi_write(), and spi_write_then_read(). These
- may be issued only in contexts that may sleep, and they're all
- clean (and small, and "optional") layers over spi_async().
-
- - The spi_write_then_read() call, and convenience wrappers around
- it, should only be used with small amounts of data where the
- cost of an extra copy may be ignored. It's designed to support
- common RPC-style requests, such as writing an eight bit command
- and reading a sixteen bit response -- spi_w8r16() being one its
- wrappers, doing exactly that.
-
-Some drivers may need to modify spi_device characteristics like the
-transfer mode, wordsize, or clock rate. This is done with spi_setup(),
-which would normally be called from probe() before the first I/O is
-done to the device. However, that can also be called at any time
-that no message is pending for that device.
-
-While "spi_device" would be the bottom boundary of the driver, the
-upper boundaries might include sysfs (especially for sensor readings),
-the input layer, ALSA, networking, MTD, the character device framework,
-or other Linux subsystems.
-
-Note that there are two types of memory your driver must manage as part
-of interacting with SPI devices.
-
- - I/O buffers use the usual Linux rules, and must be DMA-safe.
- You'd normally allocate them from the heap or free page pool.
- Don't use the stack, or anything that's declared "static".
-
- - The spi_message and spi_transfer metadata used to glue those
- I/O buffers into a group of protocol transactions. These can
- be allocated anywhere it's convenient, including as part of
- other allocate-once driver data structures. Zero-init these.
-
-If you like, spi_message_alloc() and spi_message_free() convenience
-routines are available to allocate and zero-initialize an spi_message
-with several transfers.
-
-
-How do I write an "SPI Master Controller Driver"?
--------------------------------------------------
-An SPI controller will probably be registered on the platform_bus; write
-a driver to bind to the device, whichever bus is involved.
-
-The main task of this type of driver is to provide an "spi_master".
-Use spi_alloc_master() to allocate the master, and spi_master_get_devdata()
-to get the driver-private data allocated for that device.
-
- struct spi_master *master;
- struct CONTROLLER *c;
-
- master = spi_alloc_master(dev, sizeof *c);
- if (!master)
- return -ENODEV;
-
- c = spi_master_get_devdata(master);
-
-The driver will initialize the fields of that spi_master, including the
-bus number (maybe the same as the platform device ID) and three methods
-used to interact with the SPI core and SPI protocol drivers. It will
-also initialize its own internal state. (See below about bus numbering
-and those methods.)
-
-After you initialize the spi_master, then use spi_register_master() to
-publish it to the rest of the system. At that time, device nodes for the
-controller and any predeclared spi devices will be made available, and
-the driver model core will take care of binding them to drivers.
-
-If you need to remove your SPI controller driver, spi_unregister_master()
-will reverse the effect of spi_register_master().
-
-
-BUS NUMBERING
-
-Bus numbering is important, since that's how Linux identifies a given
-SPI bus (shared SCK, MOSI, MISO). Valid bus numbers start at zero. On
-SOC systems, the bus numbers should match the numbers defined by the chip
-manufacturer. For example, hardware controller SPI2 would be bus number 2,
-and spi_board_info for devices connected to it would use that number.
-
-If you don't have such hardware-assigned bus number, and for some reason
-you can't just assign them, then provide a negative bus number. That will
-then be replaced by a dynamically assigned number. You'd then need to treat
-this as a non-static configuration (see above).
-
-
-SPI MASTER METHODS
-
- master->setup(struct spi_device *spi)
- This sets up the device clock rate, SPI mode, and word sizes.
- Drivers may change the defaults provided by board_info, and then
- call spi_setup(spi) to invoke this routine. It may sleep.
-
- Unless each SPI slave has its own configuration registers, don't
- change them right away ... otherwise drivers could corrupt I/O
- that's in progress for other SPI devices.
-
- ** BUG ALERT: for some reason the first version of
- ** many spi_master drivers seems to get this wrong.
- ** When you code setup(), ASSUME that the controller
- ** is actively processing transfers for another device.
-
- master->cleanup(struct spi_device *spi)
- Your controller driver may use spi_device.controller_state to hold
- state it dynamically associates with that device. If you do that,
- be sure to provide the cleanup() method to free that state.
-
- master->prepare_transfer_hardware(struct spi_master *master)
- This will be called by the queue mechanism to signal to the driver
- that a message is coming in soon, so the subsystem requests the
- driver to prepare the transfer hardware by issuing this call.
- This may sleep.
-
- master->unprepare_transfer_hardware(struct spi_master *master)
- This will be called by the queue mechanism to signal to the driver
- that there are no more messages pending in the queue and it may
- relax the hardware (e.g. by power management calls). This may sleep.
-
- master->transfer_one_message(struct spi_master *master,
- struct spi_message *mesg)
- The subsystem calls the driver to transfer a single message while
- queuing transfers that arrive in the meantime. When the driver is
- finished with this message, it must call
- spi_finalize_current_message() so the subsystem can issue the next
- message. This may sleep.
-
- master->transfer_one(struct spi_master *master, struct spi_device *spi,
- struct spi_transfer *transfer)
- The subsystem calls the driver to transfer a single transfer while
- queuing transfers that arrive in the meantime. When the driver is
- finished with this transfer, it must call
- spi_finalize_current_transfer() so the subsystem can issue the next
- transfer. This may sleep. Note: transfer_one and transfer_one_message
- are mutually exclusive; when both are set, the generic subsystem does
- not call your transfer_one callback.
-
- Return values:
- negative errno: error
- 0: transfer is finished
- 1: transfer is still in progress
-
- master->set_cs_timing(struct spi_device *spi, u8 setup_clk_cycles,
- u8 hold_clk_cycles, u8 inactive_clk_cycles)
- This method allows SPI client drivers to request SPI master controller
- for configuring device specific CS setup, hold and inactive timing
- requirements.
-
- DEPRECATED METHODS
-
- master->transfer(struct spi_device *spi, struct spi_message *message)
- This must not sleep. Its responsibility is to arrange that the
- transfer happens and its complete() callback is issued. The two
- will normally happen later, after other transfers complete, and
- if the controller is idle it will need to be kickstarted. This
- method is not used on queued controllers and must be NULL if
- transfer_one_message() and (un)prepare_transfer_hardware() are
- implemented.
-
-
-SPI MESSAGE QUEUE
-
-If you are happy with the standard queueing mechanism provided by the
-SPI subsystem, just implement the queued methods specified above. Using
-the message queue has the upside of centralizing a lot of code and
-providing pure process-context execution of methods. The message queue
-can also be elevated to realtime priority on high-priority SPI traffic.
-
-Unless the queueing mechanism in the SPI subsystem is selected, the bulk
-of the driver will be managing the I/O queue fed by the now deprecated
-function transfer().
-
-That queue could be purely conceptual. For example, a driver used only
-for low-frequency sensor access might be fine using synchronous PIO.
-
-But the queue will probably be very real, using message->queue, PIO,
-often DMA (especially if the root filesystem is in SPI flash), and
-execution contexts like IRQ handlers, tasklets, or workqueues (such
-as keventd). Your driver can be as fancy, or as simple, as you need.
-Such a transfer() method would normally just add the message to a
-queue, and then start some asynchronous transfer engine (unless it's
-already running).
-
-
-THANKS TO
----------
-Contributors to Linux-SPI discussions include (in alphabetical order,
-by last name):
-
-Mark Brown
-David Brownell
-Russell King
-Grant Likely
-Dmitry Pervushin
-Stephen Street
-Mark Underwood
-Andrew Victor
-Linus Walleij
-Vitaly Wool
--- /dev/null
+====================================
+Overview of Linux kernel SPI support
+====================================
+
+02-Feb-2012
+
+What is SPI?
+------------
+The "Serial Peripheral Interface" (SPI) is a synchronous four wire serial
+link used to connect microcontrollers to sensors, memory, and peripherals.
+It's a simple "de facto" standard, not complicated enough to acquire a
+standardization body. SPI uses a master/slave configuration.
+
+The three signal wires hold a clock (SCK, often on the order of 10 MHz),
+and parallel data lines with "Master Out, Slave In" (MOSI) or "Master In,
+Slave Out" (MISO) signals. (Other names are also used.) There are four
+clocking modes through which data is exchanged; mode-0 and mode-3 are most
+commonly used. Each clock cycle shifts data out and data in; the clock
+doesn't cycle except when there is a data bit to shift. Not all data bits
+are used though; not every protocol uses those full duplex capabilities.
+
+SPI masters use a fourth "chip select" line to activate a given SPI slave
+device, so those three signal wires may be connected to several chips
+in parallel. All SPI slaves support chipselects; they are usually active
+low signals, labeled nCSx for slave 'x' (e.g. nCS0). Some devices have
+other signals, often including an interrupt to the master.
+
+Unlike serial busses like USB or SMBus, even low level protocols for
+SPI slave functions are usually not interoperable between vendors
+(except for commodities like SPI memory chips).
+
+ - SPI may be used for request/response style device protocols, as with
+ touchscreen sensors and memory chips.
+
+ - It may also be used to stream data in either direction (half duplex),
+ or both of them at the same time (full duplex).
+
+ - Some devices may use eight bit words. Others may use different word
+ lengths, such as streams of 12-bit or 20-bit digital samples.
+
+ - Words are usually sent with their most significant bit (MSB) first,
+ but sometimes the least significant bit (LSB) goes first instead.
+
+ - Sometimes SPI is used to daisy-chain devices, like shift registers.
+
+In the same way, SPI slaves will only rarely support any kind of automatic
+discovery/enumeration protocol. The tree of slave devices accessible from
+a given SPI master will normally be set up manually, with configuration
+tables.
+
+SPI is only one of the names used by such four-wire protocols, and
+most controllers have no problem handling "MicroWire" (think of it as
+half-duplex SPI, for request/response protocols), SSP ("Synchronous
+Serial Protocol"), PSP ("Programmable Serial Protocol"), and other
+related protocols.
+
+Some chips eliminate a signal line by combining MOSI and MISO, and
+limiting themselves to half-duplex at the hardware level. In fact
+some SPI chips have this signal mode as a strapping option. These
+can be accessed using the same programming interface as SPI, but of
+course they won't handle full duplex transfers. You may find such
+chips described as using "three wire" signaling: SCK, data, nCSx.
+(That data line is sometimes called MOMI or SISO.)
+
+Microcontrollers often support both master and slave sides of the SPI
+protocol. This document (and Linux) supports both the master and slave
+sides of SPI interactions.
+
+
+Who uses it? On what kinds of systems?
+---------------------------------------
+Linux developers using SPI are probably writing device drivers for embedded
+systems boards. SPI is used to control external chips, and it is also a
+protocol supported by every MMC or SD memory card. (The older "DataFlash"
+cards, predating MMC cards but using the same connectors and card shape,
+support only SPI.) Some PC hardware uses SPI flash for BIOS code.
+
+SPI slave chips range from digital/analog converters used for analog
+sensors and codecs, to memory, to peripherals like USB controllers
+or Ethernet adapters; and more.
+
+Most systems using SPI will integrate a few devices on a mainboard.
+Some provide SPI links on expansion connectors; in cases where no
+dedicated SPI controller exists, GPIO pins can be used to create a
+low speed "bitbanging" adapter. Very few systems will "hotplug" an SPI
+controller; the reasons to use SPI focus on low cost and simple operation,
+and if dynamic reconfiguration is important, USB will often be a more
+appropriate low-pincount peripheral bus.
+
+Many microcontrollers that can run Linux integrate one or more I/O
+interfaces with SPI modes. Given SPI support, they could use MMC or SD
+cards without needing a special purpose MMC/SD/SDIO controller.
+
+
+I'm confused. What are these four SPI "clock modes"?
+-----------------------------------------------------
+It's easy to be confused here, and the vendor documentation you'll
+find isn't necessarily helpful. The four modes combine two mode bits:
+
+ - CPOL indicates the initial clock polarity. CPOL=0 means the
+ clock starts low, so the first (leading) edge is rising, and
+ the second (trailing) edge is falling. CPOL=1 means the clock
+ starts high, so the first (leading) edge is falling.
+
+ - CPHA indicates the clock phase used to sample data; CPHA=0 says
+ sample on the leading edge, CPHA=1 means the trailing edge.
+
+ Since the signal needs to stablize before it's sampled, CPHA=0
+ implies that its data is written half a clock before the first
+ clock edge. The chipselect may have made it become available.
+
+Chip specs won't always say "uses SPI mode X" in as many words,
+but their timing diagrams will make the CPOL and CPHA modes clear.
+
+In the SPI mode number, CPOL is the high order bit and CPHA is the
+low order bit. So when a chip's timing diagram shows the clock
+starting low (CPOL=0) and data stabilized for sampling during the
+trailing clock edge (CPHA=1), that's SPI mode 1.
+
+Note that the clock mode is relevant as soon as the chipselect goes
+active. So the master must set the clock to inactive before selecting
+a slave, and the slave can tell the chosen polarity by sampling the
+clock level when its select line goes active. That's why many devices
+support for example both modes 0 and 3: they don't care about polarity,
+and always clock data in/out on rising clock edges.
+
+
+How do these driver programming interfaces work?
+------------------------------------------------
+The <linux/spi/spi.h> header file includes kerneldoc, as does the
+main source code, and you should certainly read that chapter of the
+kernel API document. This is just an overview, so you get the big
+picture before those details.
+
+SPI requests always go into I/O queues. Requests for a given SPI device
+are always executed in FIFO order, and complete asynchronously through
+completion callbacks. There are also some simple synchronous wrappers
+for those calls, including ones for common transaction types like writing
+a command and then reading its response.
+
+There are two types of SPI driver, here called:
+
+ Controller drivers ...
+ controllers may be built into System-On-Chip
+ processors, and often support both Master and Slave roles.
+ These drivers touch hardware registers and may use DMA.
+ Or they can be PIO bitbangers, needing just GPIO pins.
+
+ Protocol drivers ...
+ these pass messages through the controller
+ driver to communicate with a Slave or Master device on the
+ other side of an SPI link.
+
+So for example one protocol driver might talk to the MTD layer to export
+data to filesystems stored on SPI flash like DataFlash; and others might
+control audio interfaces, present touchscreen sensors as input interfaces,
+or monitor temperature and voltage levels during industrial processing.
+And those might all be sharing the same controller driver.
+
+A "struct spi_device" encapsulates the controller-side interface between
+those two types of drivers.
+
+There is a minimal core of SPI programming interfaces, focussing on
+using the driver model to connect controller and protocol drivers using
+device tables provided by board specific initialization code. SPI
+shows up in sysfs in several locations::
+
+ /sys/devices/.../CTLR ... physical node for a given SPI controller
+
+ /sys/devices/.../CTLR/spiB.C ... spi_device on bus "B",
+ chipselect C, accessed through CTLR.
+
+ /sys/bus/spi/devices/spiB.C ... symlink to that physical
+ .../CTLR/spiB.C device
+
+ /sys/devices/.../CTLR/spiB.C/modalias ... identifies the driver
+ that should be used with this device (for hotplug/coldplug)
+
+ /sys/bus/spi/drivers/D ... driver for one or more spi*.* devices
+
+ /sys/class/spi_master/spiB ... symlink (or actual device node) to
+ a logical node which could hold class related state for the SPI
+ master controller managing bus "B". All spiB.* devices share one
+ physical SPI bus segment, with SCLK, MOSI, and MISO.
+
+ /sys/devices/.../CTLR/slave ... virtual file for (un)registering the
+ slave device for an SPI slave controller.
+ Writing the driver name of an SPI slave handler to this file
+ registers the slave device; writing "(null)" unregisters the slave
+ device.
+ Reading from this file shows the name of the slave device ("(null)"
+ if not registered).
+
+ /sys/class/spi_slave/spiB ... symlink (or actual device node) to
+ a logical node which could hold class related state for the SPI
+ slave controller on bus "B". When registered, a single spiB.*
+ device is present here, possible sharing the physical SPI bus
+ segment with other SPI slave devices.
+
+Note that the actual location of the controller's class state depends
+on whether you enabled CONFIG_SYSFS_DEPRECATED or not. At this time,
+the only class-specific state is the bus number ("B" in "spiB"), so
+those /sys/class entries are only useful to quickly identify busses.
+
+
+How does board-specific init code declare SPI devices?
+------------------------------------------------------
+Linux needs several kinds of information to properly configure SPI devices.
+That information is normally provided by board-specific code, even for
+chips that do support some of automated discovery/enumeration.
+
+Declare Controllers
+^^^^^^^^^^^^^^^^^^^
+
+The first kind of information is a list of what SPI controllers exist.
+For System-on-Chip (SOC) based boards, these will usually be platform
+devices, and the controller may need some platform_data in order to
+operate properly. The "struct platform_device" will include resources
+like the physical address of the controller's first register and its IRQ.
+
+Platforms will often abstract the "register SPI controller" operation,
+maybe coupling it with code to initialize pin configurations, so that
+the arch/.../mach-*/board-*.c files for several boards can all share the
+same basic controller setup code. This is because most SOCs have several
+SPI-capable controllers, and only the ones actually usable on a given
+board should normally be set up and registered.
+
+So for example arch/.../mach-*/board-*.c files might have code like::
+
+ #include <mach/spi.h> /* for mysoc_spi_data */
+
+ /* if your mach-* infrastructure doesn't support kernels that can
+ * run on multiple boards, pdata wouldn't benefit from "__init".
+ */
+ static struct mysoc_spi_data pdata __initdata = { ... };
+
+ static __init board_init(void)
+ {
+ ...
+ /* this board only uses SPI controller #2 */
+ mysoc_register_spi(2, &pdata);
+ ...
+ }
+
+And SOC-specific utility code might look something like::
+
+ #include <mach/spi.h>
+
+ static struct platform_device spi2 = { ... };
+
+ void mysoc_register_spi(unsigned n, struct mysoc_spi_data *pdata)
+ {
+ struct mysoc_spi_data *pdata2;
+
+ pdata2 = kmalloc(sizeof *pdata2, GFP_KERNEL);
+ *pdata2 = pdata;
+ ...
+ if (n == 2) {
+ spi2->dev.platform_data = pdata2;
+ register_platform_device(&spi2);
+
+ /* also: set up pin modes so the spi2 signals are
+ * visible on the relevant pins ... bootloaders on
+ * production boards may already have done this, but
+ * developer boards will often need Linux to do it.
+ */
+ }
+ ...
+ }
+
+Notice how the platform_data for boards may be different, even if the
+same SOC controller is used. For example, on one board SPI might use
+an external clock, where another derives the SPI clock from current
+settings of some master clock.
+
+Declare Slave Devices
+^^^^^^^^^^^^^^^^^^^^^
+
+The second kind of information is a list of what SPI slave devices exist
+on the target board, often with some board-specific data needed for the
+driver to work correctly.
+
+Normally your arch/.../mach-*/board-*.c files would provide a small table
+listing the SPI devices on each board. (This would typically be only a
+small handful.) That might look like::
+
+ static struct ads7846_platform_data ads_info = {
+ .vref_delay_usecs = 100,
+ .x_plate_ohms = 580,
+ .y_plate_ohms = 410,
+ };
+
+ static struct spi_board_info spi_board_info[] __initdata = {
+ {
+ .modalias = "ads7846",
+ .platform_data = &ads_info,
+ .mode = SPI_MODE_0,
+ .irq = GPIO_IRQ(31),
+ .max_speed_hz = 120000 /* max sample rate at 3V */ * 16,
+ .bus_num = 1,
+ .chip_select = 0,
+ },
+ };
+
+Again, notice how board-specific information is provided; each chip may need
+several types. This example shows generic constraints like the fastest SPI
+clock to allow (a function of board voltage in this case) or how an IRQ pin
+is wired, plus chip-specific constraints like an important delay that's
+changed by the capacitance at one pin.
+
+(There's also "controller_data", information that may be useful to the
+controller driver. An example would be peripheral-specific DMA tuning
+data or chipselect callbacks. This is stored in spi_device later.)
+
+The board_info should provide enough information to let the system work
+without the chip's driver being loaded. The most troublesome aspect of
+that is likely the SPI_CS_HIGH bit in the spi_device.mode field, since
+sharing a bus with a device that interprets chipselect "backwards" is
+not possible until the infrastructure knows how to deselect it.
+
+Then your board initialization code would register that table with the SPI
+infrastructure, so that it's available later when the SPI master controller
+driver is registered::
+
+ spi_register_board_info(spi_board_info, ARRAY_SIZE(spi_board_info));
+
+Like with other static board-specific setup, you won't unregister those.
+
+The widely used "card" style computers bundle memory, cpu, and little else
+onto a card that's maybe just thirty square centimeters. On such systems,
+your ``arch/.../mach-.../board-*.c`` file would primarily provide information
+about the devices on the mainboard into which such a card is plugged. That
+certainly includes SPI devices hooked up through the card connectors!
+
+
+Non-static Configurations
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Developer boards often play by different rules than product boards, and one
+example is the potential need to hotplug SPI devices and/or controllers.
+
+For those cases you might need to use spi_busnum_to_master() to look
+up the spi bus master, and will likely need spi_new_device() to provide the
+board info based on the board that was hotplugged. Of course, you'd later
+call at least spi_unregister_device() when that board is removed.
+
+When Linux includes support for MMC/SD/SDIO/DataFlash cards through SPI, those
+configurations will also be dynamic. Fortunately, such devices all support
+basic device identification probes, so they should hotplug normally.
+
+
+How do I write an "SPI Protocol Driver"?
+----------------------------------------
+Most SPI drivers are currently kernel drivers, but there's also support
+for userspace drivers. Here we talk only about kernel drivers.
+
+SPI protocol drivers somewhat resemble platform device drivers::
+
+ static struct spi_driver CHIP_driver = {
+ .driver = {
+ .name = "CHIP",
+ .owner = THIS_MODULE,
+ .pm = &CHIP_pm_ops,
+ },
+
+ .probe = CHIP_probe,
+ .remove = CHIP_remove,
+ };
+
+The driver core will automatically attempt to bind this driver to any SPI
+device whose board_info gave a modalias of "CHIP". Your probe() code
+might look like this unless you're creating a device which is managing
+a bus (appearing under /sys/class/spi_master).
+
+::
+
+ static int CHIP_probe(struct spi_device *spi)
+ {
+ struct CHIP *chip;
+ struct CHIP_platform_data *pdata;
+
+ /* assuming the driver requires board-specific data: */
+ pdata = &spi->dev.platform_data;
+ if (!pdata)
+ return -ENODEV;
+
+ /* get memory for driver's per-chip state */
+ chip = kzalloc(sizeof *chip, GFP_KERNEL);
+ if (!chip)
+ return -ENOMEM;
+ spi_set_drvdata(spi, chip);
+
+ ... etc
+ return 0;
+ }
+
+As soon as it enters probe(), the driver may issue I/O requests to
+the SPI device using "struct spi_message". When remove() returns,
+or after probe() fails, the driver guarantees that it won't submit
+any more such messages.
+
+ - An spi_message is a sequence of protocol operations, executed
+ as one atomic sequence. SPI driver controls include:
+
+ + when bidirectional reads and writes start ... by how its
+ sequence of spi_transfer requests is arranged;
+
+ + which I/O buffers are used ... each spi_transfer wraps a
+ buffer for each transfer direction, supporting full duplex
+ (two pointers, maybe the same one in both cases) and half
+ duplex (one pointer is NULL) transfers;
+
+ + optionally defining short delays after transfers ... using
+ the spi_transfer.delay_usecs setting (this delay can be the
+ only protocol effect, if the buffer length is zero);
+
+ + whether the chipselect becomes inactive after a transfer and
+ any delay ... by using the spi_transfer.cs_change flag;
+
+ + hinting whether the next message is likely to go to this same
+ device ... using the spi_transfer.cs_change flag on the last
+ transfer in that atomic group, and potentially saving costs
+ for chip deselect and select operations.
+
+ - Follow standard kernel rules, and provide DMA-safe buffers in
+ your messages. That way controller drivers using DMA aren't forced
+ to make extra copies unless the hardware requires it (e.g. working
+ around hardware errata that force the use of bounce buffering).
+
+ If standard dma_map_single() handling of these buffers is inappropriate,
+ you can use spi_message.is_dma_mapped to tell the controller driver
+ that you've already provided the relevant DMA addresses.
+
+ - The basic I/O primitive is spi_async(). Async requests may be
+ issued in any context (irq handler, task, etc) and completion
+ is reported using a callback provided with the message.
+ After any detected error, the chip is deselected and processing
+ of that spi_message is aborted.
+
+ - There are also synchronous wrappers like spi_sync(), and wrappers
+ like spi_read(), spi_write(), and spi_write_then_read(). These
+ may be issued only in contexts that may sleep, and they're all
+ clean (and small, and "optional") layers over spi_async().
+
+ - The spi_write_then_read() call, and convenience wrappers around
+ it, should only be used with small amounts of data where the
+ cost of an extra copy may be ignored. It's designed to support
+ common RPC-style requests, such as writing an eight bit command
+ and reading a sixteen bit response -- spi_w8r16() being one its
+ wrappers, doing exactly that.
+
+Some drivers may need to modify spi_device characteristics like the
+transfer mode, wordsize, or clock rate. This is done with spi_setup(),
+which would normally be called from probe() before the first I/O is
+done to the device. However, that can also be called at any time
+that no message is pending for that device.
+
+While "spi_device" would be the bottom boundary of the driver, the
+upper boundaries might include sysfs (especially for sensor readings),
+the input layer, ALSA, networking, MTD, the character device framework,
+or other Linux subsystems.
+
+Note that there are two types of memory your driver must manage as part
+of interacting with SPI devices.
+
+ - I/O buffers use the usual Linux rules, and must be DMA-safe.
+ You'd normally allocate them from the heap or free page pool.
+ Don't use the stack, or anything that's declared "static".
+
+ - The spi_message and spi_transfer metadata used to glue those
+ I/O buffers into a group of protocol transactions. These can
+ be allocated anywhere it's convenient, including as part of
+ other allocate-once driver data structures. Zero-init these.
+
+If you like, spi_message_alloc() and spi_message_free() convenience
+routines are available to allocate and zero-initialize an spi_message
+with several transfers.
+
+
+How do I write an "SPI Master Controller Driver"?
+-------------------------------------------------
+An SPI controller will probably be registered on the platform_bus; write
+a driver to bind to the device, whichever bus is involved.
+
+The main task of this type of driver is to provide an "spi_master".
+Use spi_alloc_master() to allocate the master, and spi_master_get_devdata()
+to get the driver-private data allocated for that device.
+
+::
+
+ struct spi_master *master;
+ struct CONTROLLER *c;
+
+ master = spi_alloc_master(dev, sizeof *c);
+ if (!master)
+ return -ENODEV;
+
+ c = spi_master_get_devdata(master);
+
+The driver will initialize the fields of that spi_master, including the
+bus number (maybe the same as the platform device ID) and three methods
+used to interact with the SPI core and SPI protocol drivers. It will
+also initialize its own internal state. (See below about bus numbering
+and those methods.)
+
+After you initialize the spi_master, then use spi_register_master() to
+publish it to the rest of the system. At that time, device nodes for the
+controller and any predeclared spi devices will be made available, and
+the driver model core will take care of binding them to drivers.
+
+If you need to remove your SPI controller driver, spi_unregister_master()
+will reverse the effect of spi_register_master().
+
+
+Bus Numbering
+^^^^^^^^^^^^^
+
+Bus numbering is important, since that's how Linux identifies a given
+SPI bus (shared SCK, MOSI, MISO). Valid bus numbers start at zero. On
+SOC systems, the bus numbers should match the numbers defined by the chip
+manufacturer. For example, hardware controller SPI2 would be bus number 2,
+and spi_board_info for devices connected to it would use that number.
+
+If you don't have such hardware-assigned bus number, and for some reason
+you can't just assign them, then provide a negative bus number. That will
+then be replaced by a dynamically assigned number. You'd then need to treat
+this as a non-static configuration (see above).
+
+
+SPI Master Methods
+^^^^^^^^^^^^^^^^^^
+
+``master->setup(struct spi_device *spi)``
+ This sets up the device clock rate, SPI mode, and word sizes.
+ Drivers may change the defaults provided by board_info, and then
+ call spi_setup(spi) to invoke this routine. It may sleep.
+
+ Unless each SPI slave has its own configuration registers, don't
+ change them right away ... otherwise drivers could corrupt I/O
+ that's in progress for other SPI devices.
+
+ .. note::
+
+ BUG ALERT: for some reason the first version of
+ many spi_master drivers seems to get this wrong.
+ When you code setup(), ASSUME that the controller
+ is actively processing transfers for another device.
+
+``master->cleanup(struct spi_device *spi)``
+ Your controller driver may use spi_device.controller_state to hold
+ state it dynamically associates with that device. If you do that,
+ be sure to provide the cleanup() method to free that state.
+
+``master->prepare_transfer_hardware(struct spi_master *master)``
+ This will be called by the queue mechanism to signal to the driver
+ that a message is coming in soon, so the subsystem requests the
+ driver to prepare the transfer hardware by issuing this call.
+ This may sleep.
+
+``master->unprepare_transfer_hardware(struct spi_master *master)``
+ This will be called by the queue mechanism to signal to the driver
+ that there are no more messages pending in the queue and it may
+ relax the hardware (e.g. by power management calls). This may sleep.
+
+``master->transfer_one_message(struct spi_master *master, struct spi_message *mesg)``
+ The subsystem calls the driver to transfer a single message while
+ queuing transfers that arrive in the meantime. When the driver is
+ finished with this message, it must call
+ spi_finalize_current_message() so the subsystem can issue the next
+ message. This may sleep.
+
+``master->transfer_one(struct spi_master *master, struct spi_device *spi, struct spi_transfer *transfer)``
+ The subsystem calls the driver to transfer a single transfer while
+ queuing transfers that arrive in the meantime. When the driver is
+ finished with this transfer, it must call
+ spi_finalize_current_transfer() so the subsystem can issue the next
+ transfer. This may sleep. Note: transfer_one and transfer_one_message
+ are mutually exclusive; when both are set, the generic subsystem does
+ not call your transfer_one callback.
+
+ Return values:
+
+ * negative errno: error
+ * 0: transfer is finished
+ * 1: transfer is still in progress
+
+``master->set_cs_timing(struct spi_device *spi, u8 setup_clk_cycles, u8 hold_clk_cycles, u8 inactive_clk_cycles)``
+ This method allows SPI client drivers to request SPI master controller
+ for configuring device specific CS setup, hold and inactive timing
+ requirements.
+
+Deprecated Methods
+^^^^^^^^^^^^^^^^^^
+
+``master->transfer(struct spi_device *spi, struct spi_message *message)``
+ This must not sleep. Its responsibility is to arrange that the
+ transfer happens and its complete() callback is issued. The two
+ will normally happen later, after other transfers complete, and
+ if the controller is idle it will need to be kickstarted. This
+ method is not used on queued controllers and must be NULL if
+ transfer_one_message() and (un)prepare_transfer_hardware() are
+ implemented.
+
+
+SPI Message Queue
+^^^^^^^^^^^^^^^^^
+
+If you are happy with the standard queueing mechanism provided by the
+SPI subsystem, just implement the queued methods specified above. Using
+the message queue has the upside of centralizing a lot of code and
+providing pure process-context execution of methods. The message queue
+can also be elevated to realtime priority on high-priority SPI traffic.
+
+Unless the queueing mechanism in the SPI subsystem is selected, the bulk
+of the driver will be managing the I/O queue fed by the now deprecated
+function transfer().
+
+That queue could be purely conceptual. For example, a driver used only
+for low-frequency sensor access might be fine using synchronous PIO.
+
+But the queue will probably be very real, using message->queue, PIO,
+often DMA (especially if the root filesystem is in SPI flash), and
+execution contexts like IRQ handlers, tasklets, or workqueues (such
+as keventd). Your driver can be as fancy, or as simple, as you need.
+Such a transfer() method would normally just add the message to a
+queue, and then start some asynchronous transfer engine (unless it's
+already running).
+
+
+THANKS TO
+---------
+Contributors to Linux-SPI discussions include (in alphabetical order,
+by last name):
+
+- Mark Brown
+- David Brownell
+- Russell King
+- Grant Likely
+- Dmitry Pervushin
+- Stephen Street
+- Mark Underwood
+- Andrew Victor
+- Linus Walleij
+- Vitaly Wool
+++ /dev/null
-SPI devices have a limited userspace API, supporting basic half-duplex
-read() and write() access to SPI slave devices. Using ioctl() requests,
-full duplex transfers and device I/O configuration are also available.
-
- #include <fcntl.h>
- #include <unistd.h>
- #include <sys/ioctl.h>
- #include <linux/types.h>
- #include <linux/spi/spidev.h>
-
-Some reasons you might want to use this programming interface include:
-
- * Prototyping in an environment that's not crash-prone; stray pointers
- in userspace won't normally bring down any Linux system.
-
- * Developing simple protocols used to talk to microcontrollers acting
- as SPI slaves, which you may need to change quite often.
-
-Of course there are drivers that can never be written in userspace, because
-they need to access kernel interfaces (such as IRQ handlers or other layers
-of the driver stack) that are not accessible to userspace.
-
-
-DEVICE CREATION, DRIVER BINDING
-===============================
-The simplest way to arrange to use this driver is to just list it in the
-spi_board_info for a device as the driver it should use: the "modalias"
-entry is "spidev", matching the name of the driver exposing this API.
-Set up the other device characteristics (bits per word, SPI clocking,
-chipselect polarity, etc) as usual, so you won't always need to override
-them later.
-
-(Sysfs also supports userspace driven binding/unbinding of drivers to
-devices. That mechanism might be supported here in the future.)
-
-When you do that, the sysfs node for the SPI device will include a child
-device node with a "dev" attribute that will be understood by udev or mdev.
-(Larger systems will have "udev". Smaller ones may configure "mdev" into
-busybox; it's less featureful, but often enough.) For a SPI device with
-chipselect C on bus B, you should see:
-
- /dev/spidevB.C ... character special device, major number 153 with
- a dynamically chosen minor device number. This is the node
- that userspace programs will open, created by "udev" or "mdev".
-
- /sys/devices/.../spiB.C ... as usual, the SPI device node will
- be a child of its SPI master controller.
-
- /sys/class/spidev/spidevB.C ... created when the "spidev" driver
- binds to that device. (Directory or symlink, based on whether
- or not you enabled the "deprecated sysfs files" Kconfig option.)
-
-Do not try to manage the /dev character device special file nodes by hand.
-That's error prone, and you'd need to pay careful attention to system
-security issues; udev/mdev should already be configured securely.
-
-If you unbind the "spidev" driver from that device, those two "spidev" nodes
-(in sysfs and in /dev) should automatically be removed (respectively by the
-kernel and by udev/mdev). You can unbind by removing the "spidev" driver
-module, which will affect all devices using this driver. You can also unbind
-by having kernel code remove the SPI device, probably by removing the driver
-for its SPI controller (so its spi_master vanishes).
-
-Since this is a standard Linux device driver -- even though it just happens
-to expose a low level API to userspace -- it can be associated with any number
-of devices at a time. Just provide one spi_board_info record for each such
-SPI device, and you'll get a /dev device node for each device.
-
-
-BASIC CHARACTER DEVICE API
-==========================
-Normal open() and close() operations on /dev/spidevB.D files work as you
-would expect.
-
-Standard read() and write() operations are obviously only half-duplex, and
-the chipselect is deactivated between those operations. Full-duplex access,
-and composite operation without chipselect de-activation, is available using
-the SPI_IOC_MESSAGE(N) request.
-
-Several ioctl() requests let your driver read or override the device's current
-settings for data transfer parameters:
-
- SPI_IOC_RD_MODE, SPI_IOC_WR_MODE ... pass a pointer to a byte which will
- return (RD) or assign (WR) the SPI transfer mode. Use the constants
- SPI_MODE_0..SPI_MODE_3; or if you prefer you can combine SPI_CPOL
- (clock polarity, idle high iff this is set) or SPI_CPHA (clock phase,
- sample on trailing edge iff this is set) flags.
- Note that this request is limited to SPI mode flags that fit in a
- single byte.
-
- SPI_IOC_RD_MODE32, SPI_IOC_WR_MODE32 ... pass a pointer to a uin32_t
- which will return (RD) or assign (WR) the full SPI transfer mode,
- not limited to the bits that fit in one byte.
-
- SPI_IOC_RD_LSB_FIRST, SPI_IOC_WR_LSB_FIRST ... pass a pointer to a byte
- which will return (RD) or assign (WR) the bit justification used to
- transfer SPI words. Zero indicates MSB-first; other values indicate
- the less common LSB-first encoding. In both cases the specified value
- is right-justified in each word, so that unused (TX) or undefined (RX)
- bits are in the MSBs.
-
- SPI_IOC_RD_BITS_PER_WORD, SPI_IOC_WR_BITS_PER_WORD ... pass a pointer to
- a byte which will return (RD) or assign (WR) the number of bits in
- each SPI transfer word. The value zero signifies eight bits.
-
- SPI_IOC_RD_MAX_SPEED_HZ, SPI_IOC_WR_MAX_SPEED_HZ ... pass a pointer to a
- u32 which will return (RD) or assign (WR) the maximum SPI transfer
- speed, in Hz. The controller can't necessarily assign that specific
- clock speed.
-
-NOTES:
-
- - At this time there is no async I/O support; everything is purely
- synchronous.
-
- - There's currently no way to report the actual bit rate used to
- shift data to/from a given device.
-
- - From userspace, you can't currently change the chip select polarity;
- that could corrupt transfers to other devices sharing the SPI bus.
- Each SPI device is deselected when it's not in active use, allowing
- other drivers to talk to other devices.
-
- - There's a limit on the number of bytes each I/O request can transfer
- to the SPI device. It defaults to one page, but that can be changed
- using a module parameter.
-
- - Because SPI has no low-level transfer acknowledgement, you usually
- won't see any I/O errors when talking to a non-existent device.
-
-
-FULL DUPLEX CHARACTER DEVICE API
-================================
-
-See the spidev_fdx.c sample program for one example showing the use of the
-full duplex programming interface. (Although it doesn't perform a full duplex
-transfer.) The model is the same as that used in the kernel spi_sync()
-request; the individual transfers offer the same capabilities as are
-available to kernel drivers (except that it's not asynchronous).
-
-The example shows one half-duplex RPC-style request and response message.
-These requests commonly require that the chip not be deselected between
-the request and response. Several such requests could be chained into
-a single kernel request, even allowing the chip to be deselected after
-each response. (Other protocol options include changing the word size
-and bitrate for each transfer segment.)
-
-To make a full duplex request, provide both rx_buf and tx_buf for the
-same transfer. It's even OK if those are the same buffer.
--- /dev/null
+=================
+SPI userspace API
+=================
+
+SPI devices have a limited userspace API, supporting basic half-duplex
+read() and write() access to SPI slave devices. Using ioctl() requests,
+full duplex transfers and device I/O configuration are also available.
+
+::
+
+ #include <fcntl.h>
+ #include <unistd.h>
+ #include <sys/ioctl.h>
+ #include <linux/types.h>
+ #include <linux/spi/spidev.h>
+
+Some reasons you might want to use this programming interface include:
+
+ * Prototyping in an environment that's not crash-prone; stray pointers
+ in userspace won't normally bring down any Linux system.
+
+ * Developing simple protocols used to talk to microcontrollers acting
+ as SPI slaves, which you may need to change quite often.
+
+Of course there are drivers that can never be written in userspace, because
+they need to access kernel interfaces (such as IRQ handlers or other layers
+of the driver stack) that are not accessible to userspace.
+
+
+DEVICE CREATION, DRIVER BINDING
+===============================
+The simplest way to arrange to use this driver is to just list it in the
+spi_board_info for a device as the driver it should use: the "modalias"
+entry is "spidev", matching the name of the driver exposing this API.
+Set up the other device characteristics (bits per word, SPI clocking,
+chipselect polarity, etc) as usual, so you won't always need to override
+them later.
+
+(Sysfs also supports userspace driven binding/unbinding of drivers to
+devices. That mechanism might be supported here in the future.)
+
+When you do that, the sysfs node for the SPI device will include a child
+device node with a "dev" attribute that will be understood by udev or mdev.
+(Larger systems will have "udev". Smaller ones may configure "mdev" into
+busybox; it's less featureful, but often enough.) For a SPI device with
+chipselect C on bus B, you should see:
+
+ /dev/spidevB.C ...
+ character special device, major number 153 with
+ a dynamically chosen minor device number. This is the node
+ that userspace programs will open, created by "udev" or "mdev".
+
+ /sys/devices/.../spiB.C ...
+ as usual, the SPI device node will
+ be a child of its SPI master controller.
+
+ /sys/class/spidev/spidevB.C ...
+ created when the "spidev" driver
+ binds to that device. (Directory or symlink, based on whether
+ or not you enabled the "deprecated sysfs files" Kconfig option.)
+
+Do not try to manage the /dev character device special file nodes by hand.
+That's error prone, and you'd need to pay careful attention to system
+security issues; udev/mdev should already be configured securely.
+
+If you unbind the "spidev" driver from that device, those two "spidev" nodes
+(in sysfs and in /dev) should automatically be removed (respectively by the
+kernel and by udev/mdev). You can unbind by removing the "spidev" driver
+module, which will affect all devices using this driver. You can also unbind
+by having kernel code remove the SPI device, probably by removing the driver
+for its SPI controller (so its spi_master vanishes).
+
+Since this is a standard Linux device driver -- even though it just happens
+to expose a low level API to userspace -- it can be associated with any number
+of devices at a time. Just provide one spi_board_info record for each such
+SPI device, and you'll get a /dev device node for each device.
+
+
+BASIC CHARACTER DEVICE API
+==========================
+Normal open() and close() operations on /dev/spidevB.D files work as you
+would expect.
+
+Standard read() and write() operations are obviously only half-duplex, and
+the chipselect is deactivated between those operations. Full-duplex access,
+and composite operation without chipselect de-activation, is available using
+the SPI_IOC_MESSAGE(N) request.
+
+Several ioctl() requests let your driver read or override the device's current
+settings for data transfer parameters:
+
+ SPI_IOC_RD_MODE, SPI_IOC_WR_MODE ...
+ pass a pointer to a byte which will
+ return (RD) or assign (WR) the SPI transfer mode. Use the constants
+ SPI_MODE_0..SPI_MODE_3; or if you prefer you can combine SPI_CPOL
+ (clock polarity, idle high iff this is set) or SPI_CPHA (clock phase,
+ sample on trailing edge iff this is set) flags.
+ Note that this request is limited to SPI mode flags that fit in a
+ single byte.
+
+ SPI_IOC_RD_MODE32, SPI_IOC_WR_MODE32 ...
+ pass a pointer to a uin32_t
+ which will return (RD) or assign (WR) the full SPI transfer mode,
+ not limited to the bits that fit in one byte.
+
+ SPI_IOC_RD_LSB_FIRST, SPI_IOC_WR_LSB_FIRST ...
+ pass a pointer to a byte
+ which will return (RD) or assign (WR) the bit justification used to
+ transfer SPI words. Zero indicates MSB-first; other values indicate
+ the less common LSB-first encoding. In both cases the specified value
+ is right-justified in each word, so that unused (TX) or undefined (RX)
+ bits are in the MSBs.
+
+ SPI_IOC_RD_BITS_PER_WORD, SPI_IOC_WR_BITS_PER_WORD ...
+ pass a pointer to
+ a byte which will return (RD) or assign (WR) the number of bits in
+ each SPI transfer word. The value zero signifies eight bits.
+
+ SPI_IOC_RD_MAX_SPEED_HZ, SPI_IOC_WR_MAX_SPEED_HZ ...
+ pass a pointer to a
+ u32 which will return (RD) or assign (WR) the maximum SPI transfer
+ speed, in Hz. The controller can't necessarily assign that specific
+ clock speed.
+
+NOTES:
+
+ - At this time there is no async I/O support; everything is purely
+ synchronous.
+
+ - There's currently no way to report the actual bit rate used to
+ shift data to/from a given device.
+
+ - From userspace, you can't currently change the chip select polarity;
+ that could corrupt transfers to other devices sharing the SPI bus.
+ Each SPI device is deselected when it's not in active use, allowing
+ other drivers to talk to other devices.
+
+ - There's a limit on the number of bytes each I/O request can transfer
+ to the SPI device. It defaults to one page, but that can be changed
+ using a module parameter.
+
+ - Because SPI has no low-level transfer acknowledgement, you usually
+ won't see any I/O errors when talking to a non-existent device.
+
+
+FULL DUPLEX CHARACTER DEVICE API
+================================
+
+See the spidev_fdx.c sample program for one example showing the use of the
+full duplex programming interface. (Although it doesn't perform a full duplex
+transfer.) The model is the same as that used in the kernel spi_sync()
+request; the individual transfers offer the same capabilities as are
+available to kernel drivers (except that it's not asynchronous).
+
+The example shows one half-duplex RPC-style request and response message.
+These requests commonly require that the chip not be deselected between
+the request and response. Several such requests could be chained into
+a single kernel request, even allowing the chip to be deselected after
+each response. (Other protocol options include changing the word size
+and bitrate for each transfer segment.)
+
+To make a full duplex request, provide both rx_buf and tx_buf for the
+same transfer. It's even OK if those are the same buffer.
* i2c:
* Documentation/i2c/writing-clients.rst
* spi:
- * Documentation/spi/spi-summary
+ * Documentation/spi/spi-summary.rst
*/
static const struct iio_sw_device_ops iio_dummy_device_ops = {
.probe = iio_dummy_probe,
help
This enables using a PXA2xx or Sodaville SSP port as a SPI master
controller. The driver can be configured to use any SSP port and
- additional documentation can be found a Documentation/spi/pxa2xx.
+ additional documentation can be found a Documentation/spi/pxa2xx.rst.
config SPI_PXA2XX_PCI
def_tristate SPI_PXA2XX && PCI && COMMON_CLK
* with a battery powered AVR microcontroller and lots of goodies. You
* can use GCC to develop firmware for this.
*
- * See Documentation/spi/butterfly for information about how to build
+ * See Documentation/spi/butterfly.rst for information about how to build
* and use this custom parallel port cable.
*/
* available (on page 4) here:
* http://www.national.com/appinfo/tempsensors/files/LM70LLPEVALmanual.pdf
*
- * Also see Documentation/spi/spi-lm70llp. The SPI<->parport code here is
+ * Also see Documentation/spi/spi-lm70llp.rst. The SPI<->parport code here is
* (heavily) based on spi-butterfly by David Brownell.
*
* The LM70 LLP connects to the PC parallel port in the following manner:
*
* Copyright (C) 2012 Guenter Roeck <linux@roeck-us.net>
*
- * For further information, see the Documentation/spi/spi-sc18is602 file.
+ * For further information, see the Documentation/spi/spi-sc18is602.rst file.
*/
/**
projects / linux-2.6-microblaze.git / commitdiff