--- /dev/null
+=== ST Microelectronics SPEAr SPI CS Driver ===
+
+SPEAr platform provides a provision to control chipselects of ARM PL022 Prime
+Cell spi controller through its system registers, which otherwise remains under
+PL022 control. If chipselect remain under PL022 control then they would be
+released as soon as transfer is over and TxFIFO becomes empty. This is not
+desired by some of the device protocols above spi which expect (multiple)
+transfers without releasing their chipselects.
+
+Chipselects can be controlled by software by turning them as GPIOs. SPEAr
+provides another interface through system registers through which software can
+directly control each PL022 chipselect. Hence, it is natural for SPEAr to export
+the control of this interface as gpio.
+
+Required properties:
+
+ * compatible: should be defined as "st,spear-spics-gpio"
+ * reg: mentioning address range of spics controller
+ * st-spics,peripcfg-reg: peripheral configuration register offset
+ * st-spics,sw-enable-bit: bit offset to enable sw control
+ * st-spics,cs-value-bit: bit offset to drive chipselect low or high
+ * st-spics,cs-enable-mask: chip select number bit mask
+ * st-spics,cs-enable-shift: chip select number program offset
+ * gpio-controller: Marks the device node as gpio controller
+ * #gpio-cells: should be 1 and will mention chip select number
+
+All the above bit offsets are within peripcfg register.
+
+Example:
+-------
+spics: spics@e0700000{
+ compatible = "st,spear-spics-gpio";
+ reg = <0xe0700000 0x1000>;
+ st-spics,peripcfg-reg = <0x3b0>;
+ st-spics,sw-enable-bit = <12>;
+ st-spics,cs-value-bit = <11>;
+ st-spics,cs-enable-mask = <3>;
+ st-spics,cs-enable-shift = <8>;
+ gpio-controller;
+ #gpio-cells = <2>;
+};
+
+
+spi0: spi@e0100000 {
+ status = "okay";
+ num-cs = <3>;
+ cs-gpios = <&gpio1 7 0>, <&spics 0>,
+ <&spics 1>;
+ ...
+}
--- /dev/null
+/*
+ * SPEAr platform SPI chipselect abstraction over gpiolib
+ *
+ * Copyright (C) 2012 ST Microelectronics
+ * Shiraz Hashim <shiraz.hashim@st.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/err.h>
+#include <linux/gpio.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+/* maximum chipselects */
+#define NUM_OF_GPIO 4
+
+/*
+ * Provision is available on some SPEAr SoCs to control ARM PL022 spi cs
+ * through system registers. This register lies outside spi (pl022)
+ * address space into system registers.
+ *
+ * It provides control for spi chip select lines so that any chipselect
+ * (out of 4 possible chipselects in pl022) can be made low to select
+ * the particular slave.
+ */
+
+/**
+ * struct spear_spics - represents spi chip select control
+ * @base: base address
+ * @perip_cfg: configuration register
+ * @sw_enable_bit: bit to enable s/w control over chipselects
+ * @cs_value_bit: bit to program high or low chipselect
+ * @cs_enable_mask: mask to select bits required to select chipselect
+ * @cs_enable_shift: bit pos of cs_enable_mask
+ * @use_count: use count of a spi controller cs lines
+ * @last_off: stores last offset caller of set_value()
+ * @chip: gpio_chip abstraction
+ */
+struct spear_spics {
+ void __iomem *base;
+ u32 perip_cfg;
+ u32 sw_enable_bit;
+ u32 cs_value_bit;
+ u32 cs_enable_mask;
+ u32 cs_enable_shift;
+ unsigned long use_count;
+ int last_off;
+ struct gpio_chip chip;
+};
+
+/* gpio framework specific routines */
+static int spics_get_value(struct gpio_chip *chip, unsigned offset)
+{
+ return -ENXIO;
+}
+
+static void spics_set_value(struct gpio_chip *chip, unsigned offset, int value)
+{
+ struct spear_spics *spics = container_of(chip, struct spear_spics,
+ chip);
+ u32 tmp;
+
+ /* select chip select from register */
+ tmp = readl_relaxed(spics->base + spics->perip_cfg);
+ if (spics->last_off != offset) {
+ spics->last_off = offset;
+ tmp &= ~(spics->cs_enable_mask << spics->cs_enable_shift);
+ tmp |= offset << spics->cs_enable_shift;
+ }
+
+ /* toggle chip select line */
+ tmp &= ~(0x1 << spics->cs_value_bit);
+ tmp |= value << spics->cs_value_bit;
+ writel_relaxed(tmp, spics->base + spics->perip_cfg);
+}
+
+static int spics_direction_input(struct gpio_chip *chip, unsigned offset)
+{
+ return -ENXIO;
+}
+
+static int spics_direction_output(struct gpio_chip *chip, unsigned offset,
+ int value)
+{
+ spics_set_value(chip, offset, value);
+ return 0;
+}
+
+static int spics_request(struct gpio_chip *chip, unsigned offset)
+{
+ struct spear_spics *spics = container_of(chip, struct spear_spics,
+ chip);
+ u32 tmp;
+
+ if (!spics->use_count++) {
+ tmp = readl_relaxed(spics->base + spics->perip_cfg);
+ tmp |= 0x1 << spics->sw_enable_bit;
+ tmp |= 0x1 << spics->cs_value_bit;
+ writel_relaxed(tmp, spics->base + spics->perip_cfg);
+ }
+
+ return 0;
+}
+
+static void spics_free(struct gpio_chip *chip, unsigned offset)
+{
+ struct spear_spics *spics = container_of(chip, struct spear_spics,
+ chip);
+ u32 tmp;
+
+ if (!--spics->use_count) {
+ tmp = readl_relaxed(spics->base + spics->perip_cfg);
+ tmp &= ~(0x1 << spics->sw_enable_bit);
+ writel_relaxed(tmp, spics->base + spics->perip_cfg);
+ }
+}
+
+static int spics_gpio_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct spear_spics *spics;
+ struct resource *res;
+ int ret;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!res) {
+ dev_err(&pdev->dev, "invalid IORESOURCE_MEM\n");
+ return -EBUSY;
+ }
+
+ spics = devm_kzalloc(&pdev->dev, sizeof(*spics), GFP_KERNEL);
+ if (!spics) {
+ dev_err(&pdev->dev, "memory allocation fail\n");
+ return -ENOMEM;
+ }
+
+ spics->base = devm_request_and_ioremap(&pdev->dev, res);
+ if (!spics->base) {
+ dev_err(&pdev->dev, "request and ioremap fail\n");
+ return -ENOMEM;
+ }
+
+ if (of_property_read_u32(np, "st-spics,peripcfg-reg",
+ &spics->perip_cfg))
+ goto err_dt_data;
+ if (of_property_read_u32(np, "st-spics,sw-enable-bit",
+ &spics->sw_enable_bit))
+ goto err_dt_data;
+ if (of_property_read_u32(np, "st-spics,cs-value-bit",
+ &spics->cs_value_bit))
+ goto err_dt_data;
+ if (of_property_read_u32(np, "st-spics,cs-enable-mask",
+ &spics->cs_enable_mask))
+ goto err_dt_data;
+ if (of_property_read_u32(np, "st-spics,cs-enable-shift",
+ &spics->cs_enable_shift))
+ goto err_dt_data;
+
+ platform_set_drvdata(pdev, spics);
+
+ spics->chip.ngpio = NUM_OF_GPIO;
+ spics->chip.base = -1;
+ spics->chip.request = spics_request;
+ spics->chip.free = spics_free;
+ spics->chip.direction_input = spics_direction_input;
+ spics->chip.direction_output = spics_direction_output;
+ spics->chip.get = spics_get_value;
+ spics->chip.set = spics_set_value;
+ spics->chip.label = dev_name(&pdev->dev);
+ spics->chip.dev = &pdev->dev;
+ spics->chip.owner = THIS_MODULE;
+ spics->last_off = -1;
+
+ ret = gpiochip_add(&spics->chip);
+ if (ret) {
+ dev_err(&pdev->dev, "unable to add gpio chip\n");
+ return ret;
+ }
+
+ dev_info(&pdev->dev, "spear spics registered\n");
+ return 0;
+
+err_dt_data:
+ dev_err(&pdev->dev, "DT probe failed\n");
+ return -EINVAL;
+}
+
+static const struct of_device_id spics_gpio_of_match[] = {
+ { .compatible = "st,spear-spics-gpio" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, spics_gpio_of_match);
+
+static struct platform_driver spics_gpio_driver = {
+ .probe = spics_gpio_probe,
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "spear-spics-gpio",
+ .of_match_table = spics_gpio_of_match,
+ },
+};
+
+static int __init spics_gpio_init(void)
+{
+ return platform_driver_register(&spics_gpio_driver);
+}
+subsys_initcall(spics_gpio_init);
+
+MODULE_AUTHOR("Shiraz Hashim <shiraz.hashim@st.com>");
+MODULE_DESCRIPTION("ST Microlectronics SPEAr SPI Chip Select Abstraction");
+MODULE_LICENSE("GPL");
projects / linux-2.6-microblaze.git / commitdiff