spi: atmel: Convert to use CS GPIO descriptors

This converts the Atmel SPI master driver to use GPIO descriptors
for chip select handling.

The Atmel driver has duplicate code to look up and initialize CS
GPIOs from the device tree, so this is removed. It further has code
to retrieve a CS GPIO from .controller_data but this seems to be
completely unused in the kernel (legacy codepath?) so I deleted
this support. It keeps track of polarity when switching the CS, but
this is not needed anymore since we moved this over to the gpiolib.

The local handling of the "npcs_pin" (I guess this might mean
"negative polarity chip select pin") is preserved, but I strongly
suspect this can be switched over to handling by the core and
using the SPI_MASTER_GPIO_SS flag on the master to assure that
the additional CS handling in the driver is also done.

Cc: Eugen Hristev <eugen.hristev@microchip.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Radu Pirea <radu.pirea@microchip.com>
Cc: Linuxarm <linuxarm@huawei.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-atmel.c

@@ -23,8 +23,7 @@
 #include <linux/of.h>
 
 #include <linux/io.h>
-#include <linux/gpio.h>
-#include <linux/of_gpio.h>
+#include <linux/gpio/consumer.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/pm_runtime.h>
 
@@ -312,7 +311,7 @@ struct atmel_spi {
 
 /* Controller-specific per-slave state */
 struct atmel_spi_device {
-	unsigned int		npcs_pin;
+	struct gpio_desc	*npcs_pin;
 	u32			csr;
 };
 
@@ -355,7 +354,6 @@ static bool atmel_spi_is_v2(struct atmel_spi *as)
 static void cs_activate(struct atmel_spi *as, struct spi_device *spi)
 {
 	struct atmel_spi_device *asd = spi->controller_state;
-	unsigned active = spi->mode & SPI_CS_HIGH;
 	u32 mr;
 
 	if (atmel_spi_is_v2(as)) {
@@ -379,7 +377,7 @@ static void cs_activate(struct atmel_spi *as, struct spi_device *spi)
 
 		mr = spi_readl(as, MR);
 		if (as->use_cs_gpios)
-			gpio_set_value(asd->npcs_pin, active);
+			gpiod_set_value(asd->npcs_pin, 1);
 	} else {
 		u32 cpol = (spi->mode & SPI_CPOL) ? SPI_BIT(CPOL) : 0;
 		int i;
@@ -396,19 +394,16 @@ static void cs_activate(struct atmel_spi *as, struct spi_device *spi)
 		mr = spi_readl(as, MR);
 		mr = SPI_BFINS(PCS, ~(1 << spi->chip_select), mr);
 		if (as->use_cs_gpios && spi->chip_select != 0)
-			gpio_set_value(asd->npcs_pin, active);
+			gpiod_set_value(asd->npcs_pin, 1);
 		spi_writel(as, MR, mr);
 	}
 
-	dev_dbg(&spi->dev, "activate %u%s, mr %08x\n",
-			asd->npcs_pin, active ? " (high)" : "",
-			mr);
+	dev_dbg(&spi->dev, "activate NPCS, mr %08x\n", mr);
 }
 
 static void cs_deactivate(struct atmel_spi *as, struct spi_device *spi)
 {
 	struct atmel_spi_device *asd = spi->controller_state;
-	unsigned active = spi->mode & SPI_CS_HIGH;
 	u32 mr;
 
 	/* only deactivate *this* device; sometimes transfers to
@@ -420,14 +415,12 @@ static void cs_deactivate(struct atmel_spi *as, struct spi_device *spi)
 		spi_writel(as, MR, mr);
 	}
 
-	dev_dbg(&spi->dev, "DEactivate %u%s, mr %08x\n",
-			asd->npcs_pin, active ? " (low)" : "",
-			mr);
+	dev_dbg(&spi->dev, "DEactivate NPCS, mr %08x\n", mr);
 
 	if (!as->use_cs_gpios)
 		spi_writel(as, CR, SPI_BIT(LASTXFER));
 	else if (atmel_spi_is_v2(as) || spi->chip_select != 0)
-		gpio_set_value(asd->npcs_pin, !active);
+		gpiod_set_value(asd->npcs_pin, 0);
 }
 
 static void atmel_spi_lock(struct atmel_spi *as) __acquires(&as->lock)
@@ -1188,7 +1181,6 @@ static int atmel_spi_setup(struct spi_device *spi)
 	struct atmel_spi_device	*asd;
 	u32			csr;
 	unsigned int		bits = spi->bits_per_word;
-	unsigned int		npcs_pin;
 
 	as = spi_master_get_devdata(spi->master);
 
@@ -1217,25 +1209,27 @@ static int atmel_spi_setup(struct spi_device *spi)
 	csr |= SPI_BF(DLYBS, 0);
 	csr |= SPI_BF(DLYBCT, 0);
 
-	/* chipselect must have been muxed as GPIO (e.g. in board setup) */
-	npcs_pin = (unsigned long)spi->controller_data;
-
-	if (!as->use_cs_gpios)
-		npcs_pin = spi->chip_select;
-	else if (gpio_is_valid(spi->cs_gpio))
-		npcs_pin = spi->cs_gpio;
-
 	asd = spi->controller_state;
 	if (!asd) {
 		asd = kzalloc(sizeof(struct atmel_spi_device), GFP_KERNEL);
 		if (!asd)
 			return -ENOMEM;
 
-		if (as->use_cs_gpios)
-			gpio_direction_output(npcs_pin,
-					      !(spi->mode & SPI_CS_HIGH));
+		/*
+		 * If use_cs_gpios is true this means that we have "cs-gpios"
+		 * defined in the device tree node so we should have
+		 * gotten the GPIO lines from the device tree inside the
+		 * SPI core. Warn if this is not the case but continue since
+		 * CS GPIOs are after all optional.
+		 */
+		if (as->use_cs_gpios) {
+			if (!spi->cs_gpiod) {
+				dev_err(&spi->dev,
+					"host claims to use CS GPIOs but no CS found in DT by the SPI core\n");
+			}
+			asd->npcs_pin = spi->cs_gpiod;
+		}
 
-		asd->npcs_pin = npcs_pin;
 		spi->controller_state = asd;
 	}
 
@@ -1473,41 +1467,6 @@ static void atmel_get_caps(struct atmel_spi *as)
 	as->caps.has_pdc_support = version < 0x212;
 }
 
-/*-------------------------------------------------------------------------*/
-static int atmel_spi_gpio_cs(struct platform_device *pdev)
-{
-	struct spi_master	*master = platform_get_drvdata(pdev);
-	struct atmel_spi	*as = spi_master_get_devdata(master);
-	struct device_node	*np = master->dev.of_node;
-	int			i;
-	int			ret = 0;
-	int			nb = 0;
-
-	if (!as->use_cs_gpios)
-		return 0;
-
-	if (!np)
-		return 0;
-
-	nb = of_gpio_named_count(np, "cs-gpios");
-	for (i = 0; i < nb; i++) {
-		int cs_gpio = of_get_named_gpio(pdev->dev.of_node,
-						"cs-gpios", i);
-
-		if (cs_gpio == -EPROBE_DEFER)
-			return cs_gpio;
-
-		if (gpio_is_valid(cs_gpio)) {
-			ret = devm_gpio_request(&pdev->dev, cs_gpio,
-						dev_name(&pdev->dev));
-			if (ret)
-				return ret;
-		}
-	}
-
-	return 0;
-}
-
 static void atmel_spi_init(struct atmel_spi *as)
 {
 	spi_writel(as, CR, SPI_BIT(SWRST));
@@ -1560,6 +1519,7 @@ static int atmel_spi_probe(struct platform_device *pdev)
 		goto out_free;
 
 	/* the spi->mode bits understood by this driver: */
+	master->use_gpio_descriptors = true;
 	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
 	master->bits_per_word_mask = SPI_BPW_RANGE_MASK(8, 16);
 	master->dev.of_node = pdev->dev.of_node;
@@ -1592,6 +1552,11 @@ static int atmel_spi_probe(struct platform_device *pdev)
 
 	atmel_get_caps(as);
 
+	/*
+	 * If there are chip selects in the device tree, those will be
+	 * discovered by the SPI core when registering the SPI master
+	 * and assigned to each SPI device.
+	 */
 	as->use_cs_gpios = true;
 	if (atmel_spi_is_v2(as) &&
 	    pdev->dev.of_node &&
@@ -1600,10 +1565,6 @@ static int atmel_spi_probe(struct platform_device *pdev)
 		master->num_chipselect = 4;
 	}
 
-	ret = atmel_spi_gpio_cs(pdev);
-	if (ret)
-		goto out_unmap_regs;
-
 	as->use_dma = false;
 	as->use_pdc = false;
 	if (as->caps.has_dma_support) {