spi: omap2-mcspi: Convert to use GPIO descriptors

The OMAP2 MCSPI has some kind of half-baked GPIO CS support:
it includes code like this:

  if (gpio_is_valid(spi->cs_gpio)) {
        ret = gpio_request(spi->cs_gpio, dev_name(&spi->dev));
	(...)

But it doesn't parse the "cs-gpios" attribute in the device
tree to count the number of GPIOs or pick out the GPIO numbers
and put these in the SPI master's .cs_gpios property.

We complete the implementation of supporting CS GPIOs
from the device tree and switch it over to use the SPI core
for this.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20200625231257.280615-1-linus.walleij@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-omap2-mcspi.c

@@ -27,7 +27,6 @@
 #include <linux/iopoll.h>
 
 #include <linux/spi/spi.h>
-#include <linux/gpio.h>
 
 #include <linux/platform_data/spi-omap2-mcspi.h>
 
@@ -1043,16 +1042,6 @@ static int omap2_mcspi_setup(struct spi_device *spi)
 		spi->controller_state = cs;
 		/* Link this to context save list */
 		list_add_tail(&cs->node, &ctx->cs);
-
-		if (gpio_is_valid(spi->cs_gpio)) {
-			ret = gpio_request(spi->cs_gpio, dev_name(&spi->dev));
-			if (ret) {
-				dev_err(&spi->dev, "failed to request gpio\n");
-				return ret;
-			}
-			gpio_direction_output(spi->cs_gpio,
-					 !(spi->mode & SPI_CS_HIGH));
-		}
 	}
 
 	ret = pm_runtime_get_sync(mcspi->dev);
@@ -1080,9 +1069,6 @@ static void omap2_mcspi_cleanup(struct spi_device *spi)
 
 		kfree(cs);
 	}
-
-	if (gpio_is_valid(spi->cs_gpio))
-		gpio_free(spi->cs_gpio);
 }
 
 static irqreturn_t omap2_mcspi_irq_handler(int irq, void *data)
@@ -1152,7 +1138,7 @@ static int omap2_mcspi_transfer_one(struct spi_master *master,
 
 	omap2_mcspi_set_enable(spi, 0);
 
-	if (gpio_is_valid(spi->cs_gpio))
+	if (spi->cs_gpiod)
 		omap2_mcspi_set_cs(spi, spi->mode & SPI_CS_HIGH);
 
 	if (par_override ||
@@ -1241,7 +1227,7 @@ static int omap2_mcspi_transfer_one(struct spi_master *master,
 
 	omap2_mcspi_set_enable(spi, 0);
 
-	if (gpio_is_valid(spi->cs_gpio))
+	if (spi->cs_gpiod)
 		omap2_mcspi_set_cs(spi, !(spi->mode & SPI_CS_HIGH));
 
 	if (mcspi->fifo_depth > 0 && t)
@@ -1431,6 +1417,7 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
 	master->dev.of_node = node;
 	master->max_speed_hz = OMAP2_MCSPI_MAX_FREQ;
 	master->min_speed_hz = OMAP2_MCSPI_MAX_FREQ >> 15;
+	master->use_gpio_descriptors = true;
 
 	platform_set_drvdata(pdev, master);