[PATCH v2] spi: mvebu_a3700_spi: add support for cs-gpios

[George Hilliard]

The device tree has a way to specify GPIO lines as chip selects.  From
the binding docs:

    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

Add support for this, while retaining backward-compatibility with
existing device trees; the driver will preserve existing behavior if a
cs-gpios list is not given, or if a particular line is specified as <0>
(native).

This implementation is inspired by similar implementations in
neighboring drivers for other platforms: atmega, mxc, etc.

Signed-off-by: George Hilliard <ghill...@amazon.com>
---
 drivers/spi/mvebu_a3700_spi.c | 40 +++++++++++++++++++++++++++++------
 1 file changed, 34 insertions(+), 6 deletions(-)

diff --git a/drivers/spi/mvebu_a3700_spi.c b/drivers/spi/mvebu_a3700_spi.c
index e860b9ec64..b82ed2ce7a 100644
--- a/drivers/spi/mvebu_a3700_spi.c
+++ b/drivers/spi/mvebu_a3700_spi.c
@@ -15,6 +15,7 @@
 #include <asm/io.h>
 #include <dm/device_compat.h>
 #include <linux/bitops.h>
+#include <asm/gpio.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -27,6 +28,7 @@ DECLARE_GLOBAL_DATA_PTR;
 #define MVEBU_SPI_A3700_SPI_EN_0               BIT(16)
 #define MVEBU_SPI_A3700_CLK_PRESCALE_MASK      0x1f
 
+#define MAX_CS_COUNT   4
 
 /* SPI registers */
 struct spi_reg {
@@ -39,16 +41,23 @@ struct spi_reg {
 struct mvebu_spi_platdata {
        struct spi_reg *spireg;
        struct clk clk;
+       struct gpio_desc cs_gpios[MAX_CS_COUNT];
 };
 
-static void spi_cs_activate(struct spi_reg *reg, int cs)
+static void spi_cs_activate(struct mvebu_spi_platdata *plat, int cs)
 {
-       setbits_le32(&reg->ctrl, MVEBU_SPI_A3700_SPI_EN_0 << cs);
+       if (CONFIG_IS_ENABLED(DM_GPIO) && dm_gpio_is_valid(&plat->cs_gpios[cs]))
+               dm_gpio_set_value(&plat->cs_gpios[cs], 1);
+       else
+               setbits_le32(&plat->spireg->ctrl, MVEBU_SPI_A3700_SPI_EN_0 << 
cs);
 }
 
-static void spi_cs_deactivate(struct spi_reg *reg, int cs)
+static void spi_cs_deactivate(struct mvebu_spi_platdata *plat, int cs)
 {
-       clrbits_le32(&reg->ctrl, MVEBU_SPI_A3700_SPI_EN_0 << cs);
+       if (CONFIG_IS_ENABLED(DM_GPIO) && dm_gpio_is_valid(&plat->cs_gpios[cs]))
+               dm_gpio_set_value(&plat->cs_gpios[cs], 0);
+       else
+               clrbits_le32(&plat->spireg->ctrl, MVEBU_SPI_A3700_SPI_EN_0 << 
cs);
 }
 
 /**
@@ -150,7 +159,7 @@ static int mvebu_spi_xfer(struct udevice *dev, unsigned int 
bitlen,
        /* Activate CS */
        if (flags & SPI_XFER_BEGIN) {
                debug("SPI: activate cs.\n");
-               spi_cs_activate(reg, spi_chip_select(dev));
+               spi_cs_activate(plat, spi_chip_select(dev));
        }
 
        /* Send and/or receive */
@@ -169,7 +178,7 @@ static int mvebu_spi_xfer(struct udevice *dev, unsigned int 
bitlen,
                        return ret;
 
                debug("SPI: deactivate cs.\n");
-               spi_cs_deactivate(reg, spi_chip_select(dev));
+               spi_cs_deactivate(plat, spi_chip_select(dev));
        }
 
        return 0;
@@ -247,6 +256,25 @@ static int mvebu_spi_probe(struct udevice *bus)
 
        writel(data, &reg->cfg);
 
+       /* Set up CS GPIOs in device tree, if any */
+       if (CONFIG_IS_ENABLED(DM_GPIO) && gpio_get_list_count(bus, "cs-gpios") 
> 0) {
+               int i;
+
+               for (i = 0; i < ARRAY_SIZE(plat->cs_gpios); i++) {
+                       ret = gpio_request_by_name(bus, "cs-gpios", i, 
&plat->cs_gpios[i], 0);
+                       if (ret < 0 || !dm_gpio_is_valid(&plat->cs_gpios[i]))
+                               // Use the native CS function for this line
+                               continue;
+
+                       ret = dm_gpio_set_dir_flags(&plat->cs_gpios[i],
+                                                   GPIOD_IS_OUT | 
GPIOD_ACTIVE_LOW);
+                       if (ret) {
+                               dev_err(bus, "Setting cs %d error\n", i);
+                               return ret;
+                       }
+               }
+       }
+
        return 0;
 }
 
-- 
2.23.3