of_spi: add generic binding support to specify cs gpio

This will allow to use gpio for chip select with no modification in the
driver binding

When use the cs-gpios, the gpio number will be passed via the cs_gpio field
and the number of chip select will automatically increased with max(hw cs, gpio cs).

So if for example the controller has 2 CS lines, and the cs-gpios
property looks like this:

cs-gpios = <&gpio1 0 0> <0> <&gpio1 1 0> <&gpio1 2 0>;

Then it should be configured so that num_chipselect = 4 with the
following mapping:

cs0 : &gpio1 0 0
cs1 : native
cs2 : &gpio1 1 0
cs3 : &gpio1 2 0

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: devicetree-discuss@lists.ozlabs.org
Cc: spi-devel-general@lists.sourceforge.net
Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
[grant.likely: fixed up type of cs count so min() can do type checking]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt
index d2c33d0f533ec8702938b017c470faf073db9032..77a8b0d39b546d9994209b2c0a47a47a46bb12f9 100644 (file)
--- a/Documentation/devicetree/bindings/spi/spi-bus.txt
+++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
@@ -12,6 +12,7 @@ The SPI master node requires the following properties:
 - #size-cells     - should be zero.
 - compatible      - name of SPI bus controller following generic names
                recommended practice.
+- cs-gpios       - (optional) gpios chip select.
 No other properties are required in the SPI bus node.  It is assumed
 that a driver for an SPI bus device will understand that it is an SPI bus.
 However, the binding does not attempt to define the specific method for
@@ -24,6 +25,22 @@ support describing the chip select layout.
 Optional property:
 - num-cs : total number of chipselects
 
+If cs-gpios is used the number of chip select will automatically increased
+with max(cs-gpios > hw cs)
+
+So if for example the controller has 2 CS lines, and the cs-gpios
+property looks like this:
+
+cs-gpios = <&gpio1 0 0> <0> <&gpio1 1 0> <&gpio1 2 0>;
+
+Then it should be configured so that num_chipselect = 4 with the
+following mapping:
+
+cs0 : &gpio1 0 0
+cs1 : native
+cs2 : &gpio1 1 0
+cs3 : &gpio1 2 0
+
 SPI slave nodes must be children of the SPI master node and can
 contain the following properties.
 - reg             - (required) chip select address of device.
@@ -37,6 +54,9 @@ contain the following properties.
 - spi-cs-high     - (optional) Empty property indicating device requires
                chip select active high
 
+If a gpio chipselect is used for the SPI slave the gpio number will be passed
+via the cs_gpio
+
 SPI example for an MPC5200 SPI bus:
        spi@f00 {
                #address-cells = <1>;

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 84c2861d6f4dde2a602e44f292c6efbd248c602b..1587a4a5ff412de0ba2a0df62b24dadfeacfa97f 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -30,6 +30,7 @@
 #include <linux/slab.h>
 #include <linux/mod_devicetable.h>
 #include <linux/spi/spi.h>
+#include <linux/of_gpio.h>
 #include <linux/pm_runtime.h>
 #include <linux/export.h>
 #include <linux/sched.h>
@@ -327,6 +328,7 @@ struct spi_device *spi_alloc_device(struct spi_master *master)
        spi->dev.parent = &master->dev;
        spi->dev.bus = &spi_bus_type;
        spi->dev.release = spidev_release;
+       spi->cs_gpio = -EINVAL;
        device_initialize(&spi->dev);
        return spi;
 }
@@ -344,15 +346,16 @@ EXPORT_SYMBOL_GPL(spi_alloc_device);
 int spi_add_device(struct spi_device *spi)
 {
        static DEFINE_MUTEX(spi_add_lock);
-       struct device *dev = spi->master->dev.parent;
+       struct spi_master *master = spi->master;
+       struct device *dev = master->dev.parent;
        struct device *d;
        int status;
 
        /* Chipselects are numbered 0..max; validate. */
-       if (spi->chip_select >= spi->master->num_chipselect) {
+       if (spi->chip_select >= master->num_chipselect) {
                dev_err(dev, "cs%d >= max %d\n",
                        spi->chip_select,
-                       spi->master->num_chipselect);
+                       master->num_chipselect);
                return -EINVAL;
        }
 
@@ -376,6 +379,9 @@ int spi_add_device(struct spi_device *spi)
                goto done;
        }
 
+       if (master->cs_gpios)
+               spi->cs_gpio = master->cs_gpios[spi->chip_select];
+
        /* Drivers may modify this initial i/o setup, but will
         * normally rely on the device being setup.  Devices
         * using SPI_CS_HIGH can't coexist well otherwise...
@@ -946,6 +952,44 @@ struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
 }
 EXPORT_SYMBOL_GPL(spi_alloc_master);
 
+#ifdef CONFIG_OF
+static int of_spi_register_master(struct spi_master *master)
+{
+       u16 nb;
+       int i, *cs;
+       struct device_node *np = master->dev.of_node;
+
+       if (!np)
+               return 0;
+
+       nb = of_gpio_named_count(np, "cs-gpios");
+       master->num_chipselect = max(nb, master->num_chipselect);
+
+       if (nb < 1)
+               return 0;
+
+       cs = devm_kzalloc(&master->dev,
+                         sizeof(int) * master->num_chipselect,
+                         GFP_KERNEL);
+       master->cs_gpios = cs;
+
+       if (!master->cs_gpios)
+               return -ENOMEM;
+
+       memset(cs, -EINVAL, master->num_chipselect);
+
+       for (i = 0; i < nb; i++)
+               cs[i] = of_get_named_gpio(np, "cs-gpios", i);
+
+       return 0;
+}
+#else
+static int of_spi_register_master(struct spi_master *master)
+{
+       return 0;
+}
+#endif
+
 /**
  * spi_register_master - register SPI master controller
  * @master: initialized master, originally from spi_alloc_master()
@@ -977,6 +1021,10 @@ int spi_register_master(struct spi_master *master)
        if (!dev)
                return -ENODEV;
 
+       status = of_spi_register_master(master);
+       if (status)
+               return status;
+
        /* even if it's just one always-selected device, there must
         * be at least one chipselect
         */

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index fa702aeb5038d40b096e61cc65ba1b8d54d7ef39..f62918946d86502ed69b6668ee677c7abea343eb 100644 (file)
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -90,6 +90,7 @@ struct spi_device {
        void                    *controller_state;
        void                    *controller_data;
        char                    modalias[SPI_NAME_SIZE];
+       int                     cs_gpio;        /* chip select gpio */
 
        /*
         * likely need more hooks for more protocol options affecting how
@@ -362,6 +363,8 @@ struct spi_master {
        int (*transfer_one_message)(struct spi_master *master,
                                    struct spi_message *mesg);
        int (*unprepare_transfer_hardware)(struct spi_master *master);
+       /* gpio chip select */
+       int                     *cs_gpios;
 };
 
 static inline void *spi_master_get_devdata(struct spi_master *master)