spi: spi-gpio: Add dt support for a single device with no chip select

In order to describe a single slave device that has no chip select line
the 'num-chipselects' property has to be <0> and the 'cs-gpios' property
doesn't need to be set.

Signed-off-by: Torsten Fleischer <torfl6749@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

2 files changed, 19 insertions, 8 deletions

diff --git a/Documentation/devicetree/bindings/spi/spi-gpio.txt b/Documentation/devicetree/bindings/spi/spi-gpio.txt
index 8a824be15754..a95603bcf6ff 100644
--- a/Documentation/devicetree/bindings/spi/spi-gpio.txt
+++ b/Documentation/devicetree/bindings/spi/spi-gpio.txt
@@ -8,8 +8,10 @@ Required properties:
  - 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
+ - cs-gpios: GPIOs to use for chipselect lines.
+             Not needed if num-chipselects = <0>.
+ - num-chipselects: Number of chipselect lines. Should be <0> if a single device
+                    with no chip select is connected.
 
 Example:
 
diff --git a/drivers/spi/spi-gpio.c b/drivers/spi/spi-gpio.c
index 9f595535cf27..f0492c99d145 100644
--- a/drivers/spi/spi-gpio.c
+++ b/drivers/spi/spi-gpio.c
@@ -413,6 +413,7 @@ static int spi_gpio_probe(struct platform_device *pdev)
         struct spi_gpio_platform_data   *pdata;
         u16 master_flags = 0;
         bool use_of = 0;
+        int num_devices;
 
         status = spi_gpio_probe_dt(pdev);
         if (status < 0)
@@ -422,16 +423,21 @@ static int spi_gpio_probe(struct platform_device *pdev)
 
         pdata = dev_get_platdata(&pdev->dev);
 #ifdef GENERIC_BITBANG
-        if (!pdata || !pdata->num_chipselect)
+        if (!pdata || (!use_of && !pdata->num_chipselect))
                 return -ENODEV;
 #endif
 
+        if (use_of && !SPI_N_CHIPSEL)
+                num_devices = 1;
+        else
+                num_devices = SPI_N_CHIPSEL;
+
         status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags);
         if (status < 0)
                 return status;
 
         master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio) +
-                                        (sizeof(int) * SPI_N_CHIPSEL));
+                                        (sizeof(int) * num_devices));
         if (!master) {
                 status = -ENOMEM;
                 goto gpio_free;
@@ -446,7 +452,7 @@ static int spi_gpio_probe(struct platform_device *pdev)
         master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
         master->flags = master_flags;
         master->bus_num = pdev->id;
-        master->num_chipselect = SPI_N_CHIPSEL;
+        master->num_chipselect = num_devices;
         master->setup = spi_gpio_setup;
         master->cleanup = spi_gpio_cleanup;
 #ifdef CONFIG_OF
@@ -461,9 +467,12 @@ static int spi_gpio_probe(struct platform_device *pdev)
                  * 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);
+                if (!SPI_N_CHIPSEL)
+                        spi_gpio->cs_gpios[0] = SPI_GPIO_NO_CHIPSELECT;
+                else
+                        for (i = 0; i < SPI_N_CHIPSEL; i++)
+                                spi_gpio->cs_gpios[i] =
+                                        of_get_named_gpio(np, "cs-gpios", i);
         }
 #endif