spi: dw: Add support for 32-bits max xfer size

The Synopsis DesignWare DW_apb_ssi specifications version 3.23 onward
define a 32-bits maximum transfer size synthesis parameter
(SSI_MAX_XFER_SIZE=32) in addition to the legacy 16-bits configuration
(SSI_MAX_XFER_SIZE=16) for SPI controllers. When SSI_MAX_XFER_SIZE=32,
the layout of the ctrlr0 register changes, moving the data frame format
field from bits [3..0] to bits [16..20], and the RX/TX FIFO word size
can be up to 32-bits.

To support this new format, introduce the DW SPI capability flag
DW_SPI_CAP_DFS32 to indicate that a controller is configured with
SSI_MAX_XFER_SIZE=32. Since SSI_MAX_XFER_SIZE is a controller synthesis
parameter not accessible through a register, the detection of this
parameter value is done in spi_hw_init() by writing and reading the
ctrlr0 register and testing the value of bits [3..0]. These bits are
ignored (unchanged) for SSI_MAX_XFER_SIZE=16, allowing the detection.
If a DFS32 capable SPI controller is detected, the new field dfs_offset
in struct dw_spi is set to SPI_DFS32_OFFSET (16).

dw_spi_update_config() is modified to set the data frame size field at
the correct position is the CTRLR0 register, as indicated by the
dfs_offset field of the dw_spi structure.

The DW_SPI_CAP_DFS32 flag is also unconditionally set for SPI slave
controllers, e.g. controllers that have the DW_SPI_CAP_DWC_SSI
capability flag set. However, for these ssi controllers, the dfs_offset
field is set to 0 as before (as per specifications).

Finally, for any controller with the DW_SPI_CAP_DFS32 capability flag
set, dw_spi_add_host() extends the value of bits_per_word_mask from
16-bits to 32-bits. dw_reader() and dw_writer() are also modified to
handle 32-bits iTX/RX FIFO words.

Suggested-by: Sean Anderson <seanga2@gmail.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Acked-by: Serge Semin <fancer.lancer@gmail.com>
Link: https://lore.kernel.org/r/20201206011817.11700-3-damien.lemoal@wdc.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
index c33866f..a305074 100644 (file)
--- a/drivers/spi/spi-dw-core.c
+++ b/drivers/spi/spi-dw-core.c
@@ -137,14 +137,16 @@ static inline u32 rx_max(struct dw_spi *dws)
 static void dw_writer(struct dw_spi *dws)
 {
        u32 max = tx_max(dws);
-       u16 txw = 0;
+       u32 txw = 0;
 
        while (max--) {
                if (dws->tx) {
                        if (dws->n_bytes == 1)
                                txw = *(u8 *)(dws->tx);
-                       else
+                       else if (dws->n_bytes == 2)
                                txw = *(u16 *)(dws->tx);
+                       else
+                               txw = *(u32 *)(dws->tx);
 
                        dws->tx += dws->n_bytes;
                }
@@ -156,15 +158,17 @@ static void dw_writer(struct dw_spi *dws)
 static void dw_reader(struct dw_spi *dws)
 {
        u32 max = rx_max(dws);
-       u16 rxw;
+       u32 rxw;
 
        while (max--) {
                rxw = dw_read_io_reg(dws, DW_SPI_DR);
                if (dws->rx) {
                        if (dws->n_bytes == 1)
                                *(u8 *)(dws->rx) = rxw;
-                       else
+                       else if (dws->n_bytes == 2)
                                *(u16 *)(dws->rx) = rxw;
+                       else
+                               *(u32 *)(dws->rx) = rxw;
 
                        dws->rx += dws->n_bytes;
                }
@@ -311,8 +315,8 @@ void dw_spi_update_config(struct dw_spi *dws, struct spi_device *spi,
        u32 speed_hz;
        u16 clk_div;
 
-       /* CTRLR0[ 4/3: 0] Data Frame Size */
-       cr0 |= (cfg->dfs - 1);
+       /* CTRLR0[ 4/3: 0] or CTRLR0[ 20: 16] Data Frame Size */
+       cr0 |= (cfg->dfs - 1) << dws->dfs_offset;
 
        if (!(dws->caps & DW_SPI_CAP_DWC_SSI))
                /* CTRLR0[ 9:8] Transfer Mode */
@@ -828,6 +832,29 @@ static void spi_hw_init(struct device *dev, struct dw_spi *dws)
                dev_dbg(dev, "Detected FIFO size: %u bytes\n", dws->fifo_len);
        }
 
+       /*
+        * Detect CTRLR0.DFS field size and offset by testing the lowest bits
+        * writability. Note DWC SSI controller also has the extended DFS, but
+        * with zero offset.
+        */
+       if (!(dws->caps & DW_SPI_CAP_DWC_SSI)) {
+               u32 cr0, tmp = dw_readl(dws, DW_SPI_CTRLR0);
+
+               spi_enable_chip(dws, 0);
+               dw_writel(dws, DW_SPI_CTRLR0, 0xffffffff);
+               cr0 = dw_readl(dws, DW_SPI_CTRLR0);
+               dw_writel(dws, DW_SPI_CTRLR0, tmp);
+               spi_enable_chip(dws, 1);
+
+               if (!(cr0 & SPI_DFS_MASK)) {
+                       dws->caps |= DW_SPI_CAP_DFS32;
+                       dws->dfs_offset = SPI_DFS32_OFFSET;
+                       dev_dbg(dev, "Detected 32-bits max data frame size\n");
+               }
+       } else {
+               dws->caps |= DW_SPI_CAP_DFS32;
+       }
+
        /* enable HW fixup for explicit CS deselect for Amazon's alpine chip */
        if (dws->caps & DW_SPI_CAP_CS_OVERRIDE)
                dw_writel(dws, DW_SPI_CS_OVERRIDE, 0xF);
@@ -864,7 +891,10 @@ int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
 
        master->use_gpio_descriptors = true;
        master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP;
-       master->bits_per_word_mask =  SPI_BPW_RANGE_MASK(4, 16);
+       if (dws->caps & DW_SPI_CAP_DFS32)
+               master->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 32);
+       else
+               master->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 16);
        master->bus_num = dws->bus_num;
        master->num_chipselect = dws->num_cs;
        master->setup = dw_spi_setup;

diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h
index faf40cb..b665e04 100644 (file)
--- a/drivers/spi/spi-dw.h
+++ b/drivers/spi/spi-dw.h
@@ -9,6 +9,7 @@
 #include <linux/io.h>
 #include <linux/scatterlist.h>
 #include <linux/spi/spi-mem.h>
+#include <linux/bitfield.h>
 
 /* Register offsets */
 #define DW_SPI_CTRLR0                  0x00
@@ -41,6 +42,8 @@
 
 /* Bit fields in CTRLR0 */
 #define SPI_DFS_OFFSET                 0
+#define SPI_DFS_MASK                   GENMASK(3, 0)
+#define SPI_DFS32_OFFSET               16
 
 #define SPI_FRF_OFFSET                 4
 #define SPI_FRF_SPI                    0x0
@@ -121,6 +124,7 @@ enum dw_ssi_type {
 #define DW_SPI_CAP_CS_OVERRIDE         BIT(0)
 #define DW_SPI_CAP_KEEMBAY_MST         BIT(1)
 #define DW_SPI_CAP_DWC_SSI             BIT(2)
+#define DW_SPI_CAP_DFS32               BIT(3)
 
 /* Slave spi_transfer/spi_mem_op related */
 struct dw_spi_cfg {
@@ -148,6 +152,7 @@ struct dw_spi {
        unsigned long           paddr;
        int                     irq;
        u32                     fifo_len;       /* depth of the FIFO buffer */
+       unsigned int            dfs_offset;     /* CTRLR0 DFS field offset */
        u32                     max_mem_freq;   /* max mem-ops bus freq */
        u32                     max_freq;       /* max bus freq supported */