spi: spi-gpio: Add DT bindings

This patch adds DT bindings to the spi-gpio driver and some
documentation about how to use it.

Signed-off-by: Daniel Mack <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

Documentation/devicetree/bindings/spi/spi-gpio.txt

···
+SPI-GPIO devicetree bindings
+
+Required properties:
+
+ - compatible: should be set to "spi-gpio"
+ - #address-cells: should be set to <0x1>
+ - ranges
+ - gpio-sck: GPIO spec for the SCK line to use
+ - gpio-miso: GPIO spec for the MISO line to use
+ - gpio-mosi: GPIO spec for the MOSI line to use
+ - cs-gpios: GPIOs to use for chipselect lines
+ - num-chipselects: number of chipselect lines
+
+Example:
+
+	spi {
+		compatible = "spi-gpio";
+		#address-cells = <0x1>;
+		ranges;
+
+		gpio-sck = <&gpio 95 0>;
+		gpio-miso = <&gpio 98 0>;
+		gpio-mosi = <&gpio 97 0>;
+		cs-gpios = <&gpio 125 0>;
+		num-chipselects = <1>;
+
+		/* clients */
+	};
+

drivers/spi/spi-gpio.c

···
 #include <linux/init.h>
 #include <linux/platform_device.h>
 #include <linux/gpio.h>
+#include <linux/of_device.h>
+#include <linux/of_gpio.h>
 
 #include <linux/spi/spi.h>
 #include <linux/spi/spi_bitbang.h>
···
 
 static int spi_gpio_setup(struct spi_device *spi)
 {
-	unsigned int		cs = (unsigned int) spi->controller_data;
+	unsigned int		cs;
 	int			status = 0;
 	struct spi_gpio		*spi_gpio = spi_to_spi_gpio(spi);
+	struct device_node	*np = spi->master->dev.of_node;
 
 	if (spi->bits_per_word > 32)
 		return -EINVAL;
+
+	if (np) {
+		/*
+		 * In DT environments, the CS GPIOs have already been
+		 * initialized from the "cs-gpios" property of the node.
+		 */
+		cs = spi_gpio->cs_gpios[spi->chip_select];
+	} else {
+		/*
+		 * ... otherwise, take it from spi->controller_data
+		 */
+		cs = (unsigned int) spi->controller_data;
+	}
 
 	if (!spi->controller_state) {
 		if (cs != SPI_GPIO_NO_CHIPSELECT) {
···
 	}
 	if (!status) {
 		status = spi_bitbang_setup(spi);
+		/* in case it was initialized from static board data */
 		spi_gpio->cs_gpios[spi->chip_select] = cs;
 	}
 
···
 	return value;
 }
 
+#ifdef CONFIG_OF
+static struct of_device_id spi_gpio_dt_ids[] = {
+	{ .compatible = "spi-gpio" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids);
+
+static int spi_gpio_probe_dt(struct platform_device *pdev)
+{
+	int ret;
+	u32 tmp;
+	struct spi_gpio_platform_data	*pdata;
+	struct device_node *np = pdev->dev.of_node;
+	const struct of_device_id *of_id =
+			of_match_device(spi_gpio_dt_ids, &pdev->dev);
+
+	if (!of_id)
+		return 0;
+
+	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return -ENOMEM;
+
+	pdata->sck = of_get_named_gpio(np, "gpio-sck", 0);
+	pdata->miso = of_get_named_gpio(np, "gpio-miso", 0);
+	pdata->mosi = of_get_named_gpio(np, "gpio-mosi", 0);
+
+	ret = of_property_read_u32(np, "num-chipselects", &tmp);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "num-chipselects property not found\n");
+		goto error_free;
+	}
+
+	pdata->num_chipselect = tmp;
+	pdev->dev.platform_data = pdata;
+
+	return 1;
+
+error_free:
+	devm_kfree(&pdev->dev, pdata);
+	return ret;
+}
+#else
+static inline int spi_probe_dt(struct platform_device *)
+{
+	return 0;
+}
+#endif
+
 static int __devinit spi_gpio_probe(struct platform_device *pdev)
 {
 	int				status;
···
 	struct spi_gpio			*spi_gpio;
 	struct spi_gpio_platform_data	*pdata;
 	u16 master_flags = 0;
+	bool use_of = 0;
+
+	status = spi_gpio_probe_dt(pdev);
+	if (status < 0)
+		return status;
+	if (status > 0)
+		use_of = 1;
 
 	pdata = pdev->dev.platform_data;
 #ifdef GENERIC_BITBANG
···
 	master->num_chipselect = SPI_N_CHIPSEL;
 	master->setup = spi_gpio_setup;
 	master->cleanup = spi_gpio_cleanup;
+#ifdef CONFIG_OF
+	master->dev.of_node = pdev->dev.of_node;
+
+	if (use_of) {
+		int i;
+		struct device_node *np = pdev->dev.of_node;
+
+		/*
+		 * In DT environments, take the CS GPIO from the "cs-gpios"
+		 * property of the node.
+		 */
+
+		for (i = 0; i < SPI_N_CHIPSEL; i++)
+			spi_gpio->cs_gpios[i] =
+				of_get_named_gpio(np, "cs-gpios", i);
+	}
+#endif
 
 	spi_gpio->bitbang.master = spi_master_get(master);
 	spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
···
 MODULE_ALIAS("platform:" DRIVER_NAME);
 
 static struct platform_driver spi_gpio_driver = {
-	.driver.name	= DRIVER_NAME,
-	.driver.owner	= THIS_MODULE,
+	.driver = {
+		.name	= DRIVER_NAME,
+		.owner	= THIS_MODULE,
+		.of_match_table = of_match_ptr(spi_gpio_dt_ids),
+	},
 	.probe		= spi_gpio_probe,
 	.remove		= __devexit_p(spi_gpio_remove),
 };