spi: sh-msiof: Implement cs-gpios configuration

The current support for GPIO chip selects assumes the GPIOs have been
configured by platform code or the boot loader.  This includes pinmux
setup and GPIO direction.  Hence it does not work as expected when just
described in DT using the "cs-gpios" property.

Fix this by:
  1. using devm_gpiod_get_index() to request the GPIO, and thus
     configure pinmux, if needed,
  2. configuring the GPIO direction is the spi_master.setup() callback.

Use gpio_is_valid() instead of a check on positive numbers.

Note that when using GPIO chip selects, at least one native chip select
must be left unused, as that native chip select will be driven anyway,
and (global) native chip select polarity must be taken into account.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-sh-msiof.c

@@ -19,6 +19,7 @@
 #include <linux/dmaengine.h>
 #include <linux/err.h>
 #include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
@@ -55,6 +56,7 @@ struct sh_msiof_spi_priv {
 	void *rx_dma_page;
 	dma_addr_t tx_dma_addr;
 	dma_addr_t rx_dma_addr;
+	unsigned short unused_ss;
 	bool native_cs_inited;
 	bool native_cs_high;
 	bool slave_aborted;
@@ -547,8 +549,8 @@ static int sh_msiof_spi_setup(struct spi_device *spi)
 		spi->cs_gpio = (uintptr_t)spi->controller_data;
 	}
 
-	if (spi->cs_gpio >= 0) {
-		gpio_set_value(spi->cs_gpio, !(spi->mode & SPI_CS_HIGH));
+	if (gpio_is_valid(spi->cs_gpio)) {
+		gpio_direction_output(spi->cs_gpio, !(spi->mode & SPI_CS_HIGH));
 		return 0;
 	}
 
@@ -580,14 +582,20 @@ static int sh_msiof_prepare_message(struct spi_master *master,
 {
 	struct sh_msiof_spi_priv *p = spi_master_get_devdata(master);
 	const struct spi_device *spi = msg->spi;
+	u32 ss, cs_high;
 
 	/* Configure pins before asserting CS */
-	sh_msiof_spi_set_pin_regs(p, spi->chip_select,
-				  !!(spi->mode & SPI_CPOL),
+	if (gpio_is_valid(spi->cs_gpio)) {
+		ss = p->unused_ss;
+		cs_high = p->native_cs_high;
+	} else {
+		ss = spi->chip_select;
+		cs_high = !!(spi->mode & SPI_CS_HIGH);
+	}
+	sh_msiof_spi_set_pin_regs(p, ss, !!(spi->mode & SPI_CPOL),
 				  !!(spi->mode & SPI_CPHA),
 				  !!(spi->mode & SPI_3WIRE),
-				  !!(spi->mode & SPI_LSB_FIRST),
-				  !!(spi->mode & SPI_CS_HIGH));
+				  !!(spi->mode & SPI_LSB_FIRST), cs_high);
 	return 0;
 }
 
@@ -1091,6 +1099,45 @@ static struct sh_msiof_spi_info *sh_msiof_spi_parse_dt(struct device *dev)
 }
 #endif
 
+static int sh_msiof_get_cs_gpios(struct sh_msiof_spi_priv *p)
+{
+	struct device *dev = &p->pdev->dev;
+	unsigned int used_ss_mask = 0;
+	unsigned int cs_gpios = 0;
+	unsigned int num_cs, i;
+	int ret;
+
+	ret = gpiod_count(dev, "cs");
+	if (ret <= 0)
+		return 0;
+
+	num_cs = max_t(unsigned int, ret, p->master->num_chipselect);
+	for (i = 0; i < num_cs; i++) {
+		struct gpio_desc *gpiod;
+
+		gpiod = devm_gpiod_get_index(dev, "cs", i, GPIOD_ASIS);
+		if (!IS_ERR(gpiod)) {
+			cs_gpios++;
+			continue;
+		}
+
+		if (PTR_ERR(gpiod) != -ENOENT)
+			return PTR_ERR(gpiod);
+
+		if (i >= MAX_SS) {
+			dev_err(dev, "Invalid native chip select %d\n", i);
+			return -EINVAL;
+		}
+		used_ss_mask |= BIT(i);
+	}
+	p->unused_ss = ffz(used_ss_mask);
+	if (cs_gpios && p->unused_ss >= MAX_SS) {
+		dev_err(dev, "No unused native chip select available\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
 static struct dma_chan *sh_msiof_request_dma_chan(struct device *dev,
 	enum dma_transfer_direction dir, unsigned int id, dma_addr_t port_addr)
 {
@@ -1304,13 +1351,18 @@ static int sh_msiof_spi_probe(struct platform_device *pdev)
 	if (p->info->rx_fifo_override)
 		p->rx_fifo_size = p->info->rx_fifo_override;
 
+	/* Setup GPIO chip selects */
+	master->num_chipselect = p->info->num_chipselect;
+	ret = sh_msiof_get_cs_gpios(p);
+	if (ret)
+		goto err1;
+
 	/* init master code */
 	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
 	master->mode_bits |= SPI_LSB_FIRST | SPI_3WIRE;
 	master->flags = chipdata->master_flags;
 	master->bus_num = pdev->id;
 	master->dev.of_node = pdev->dev.of_node;
-	master->num_chipselect = p->info->num_chipselect;
 	master->setup = sh_msiof_spi_setup;
 	master->prepare_message = sh_msiof_prepare_message;
 	master->slave_abort = sh_msiof_slave_abort;