[PATCH v2 06/12] spi: add support to handle cs-gpios

[Marco Felsch]

At the moment all drivers have to parse the cs-gpios on their own and
have to implement the mapping. By this commit we add the support to
handle this within the core and if there is valid CS GPIO for a device
we assign it accordingly.

Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
---
Changelog:
v2:
 - add missing 'use_gpio_descriptor' member documentation

 drivers/spi/spi.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++
 include/spi/spi.h | 12 +++++++++
 2 files changed, 78 insertions(+)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 36d0653a191c..c239de9d8549 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -8,6 +8,8 @@
  */
 
 #include <common.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
 #include <linux/spi/spi-mem.h>
 #include <spi/spi.h>
 #include <xfuncs.h>
@@ -64,6 +66,8 @@ struct spi_device *spi_new_device(struct spi_controller *ctrl,
 	proxy = xzalloc(sizeof *proxy);
 	proxy->master = ctrl;
 	proxy->chip_select = chip->chip_select;
+	if (ctrl->cs_gpiods)
+		proxy->cs_gpiod = ctrl->cs_gpiods[chip->chip_select];
 	proxy->max_speed_hz = chip->max_speed_hz;
 	proxy->mode = chip->mode;
 	proxy->bits_per_word = chip->bits_per_word ? chip->bits_per_word : 8;
@@ -215,6 +219,62 @@ static void scan_boardinfo(struct spi_controller *ctrl)
 	}
 }
 
+/**
+ * spi_get_gpio_descs() - grab chip select GPIOs for the master
+ * @ctlr: The SPI master to grab GPIO descriptors for
+ */
+static int spi_get_gpio_descs(struct spi_controller *ctlr)
+{
+	int nb, i;
+	struct gpio_desc **cs;
+	struct device *dev = ctlr->dev;
+
+	nb = gpiod_count(dev, "cs");
+	if (nb < 0) {
+		/* No GPIOs at all is fine, else return the error */
+		if (nb == -ENOENT)
+			return 0;
+		return nb;
+	}
+
+	ctlr->num_chipselect = max_t(int, nb, ctlr->num_chipselect);
+
+	cs = devm_kcalloc(dev, ctlr->num_chipselect, sizeof(*cs),
+			  GFP_KERNEL);
+	if (!cs)
+		return -ENOMEM;
+	ctlr->cs_gpiods = cs;
+
+	for (i = 0; i < nb; i++) {
+		/*
+		 * Most chipselects are active low, the inverted
+		 * semantics are handled by special quirks in gpiolib,
+		 * so initializing them GPIOD_OUT_LOW here means
+		 * "unasserted", in most cases this will drive the physical
+		 * line high.
+		 */
+		cs[i] = gpiod_get_index_optional(dev, "cs", i, GPIOD_OUT_LOW);
+		if (IS_ERR(cs[i]))
+			return PTR_ERR(cs[i]);
+
+		if (cs[i]) {
+			/*
+			 * If we find a CS GPIO, name it after the device and
+			 * chip select line.
+			 */
+			char *gpioname;
+
+			gpioname = basprintf("%s CS%d", dev_name(dev), i);
+			if (!gpioname)
+				return -ENOMEM;
+			gpiod_set_consumer_name(cs[i], gpioname);
+			free(gpioname);
+		}
+	}
+
+	return 0;
+}
+
 static int spi_controller_check_ops(struct spi_controller *ctlr)
 {
 	/*
@@ -285,6 +345,12 @@ int spi_register_controller(struct spi_controller *ctrl)
 	if (ctrl->bus_num < 0)
 		ctrl->bus_num = dyn_bus_id--;
 
+	if (ctrl->use_gpio_descriptors) {
+		status = spi_get_gpio_descs(ctrl);
+		if (status)
+			return status;
+	}
+
 	list_add_tail(&ctrl->list, &spi_controller_list);
 
 	spi_of_register_slaves(ctrl);
diff --git a/include/spi/spi.h b/include/spi/spi.h
index 9261d508befd..d643b83a7dbb 100644
--- a/include/spi/spi.h
+++ b/include/spi/spi.h
@@ -8,6 +8,7 @@
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <linux/bitops.h>
+#include <linux/gpio/consumer.h>
 
 struct spi_controller_mem_ops;
 struct spi_message;
@@ -99,6 +100,7 @@ struct spi_device {
 	void			*controller_state;
 	void			*controller_data;
 	const char		*modalias;
+	struct gpio_desc	*cs_gpiod;	/* Chip select gpio desc */
 
 	/*
 	 * likely need more hooks for more protocol options affecting how
@@ -156,6 +158,12 @@ static inline void spi_set_ctldata(struct spi_device *spi, void *state)
  *	the device whose settings are being modified.
  * @transfer: adds a message to the controller's transfer queue.
  * @cleanup: frees controller-specific state
+ * @cs_gpiods: Array of GPIO descriptors to use as chip select lines; one per CS
+ *	number. Any individual value may be NULL for CS lines that
+ *	are not GPIOs (driven by the SPI controller itself).
+ * @use_gpio_descriptors: Turns on the code in the SPI core to parse and grab
+ *	GPIO descriptors. This will fill in @cs_gpiods and SPI devices will have
+ *	the cs_gpiod assigned if a GPIO line is found for the chipselect.
  * @list: link with the global spi_controller list
  *
  * Each SPI controller can communicate with one or more @spi_device
@@ -233,6 +241,10 @@ struct spi_controller {
 	/* called on release() to free memory provided by spi_controller */
 	void			(*cleanup)(struct spi_device *spi);
 
+	/* GPIO chip select */
+	struct gpio_desc	**cs_gpiods;
+	bool			use_gpio_descriptors;
+
 	struct list_head list;
 };
 
-- 
2.39.5