spi: orion: Handle GPIO chip-selects

Some hardware designs use GPIOs to add (or supplement) the SPI
chip-select so that more than one SPI slave device can be used.

For this to work with the spi-orion driver the SPI_MASTER_GPIO_SS flag
needs to be set (because the other outputs are gated internally by the
CS) and the correct chip-select (in this case CS0) needs to be driven by
the controller.
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-orion.c

@@ -22,6 +22,7 @@
 #include <linux/of_device.h>
 #include <linux/clk.h>
 #include <linux/sizes.h>
+#include <linux/gpio.h>
 #include <asm/unaligned.h>
 
 #define DRIVER_NAME			"orion_spi"
@@ -320,12 +321,18 @@ orion_spi_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
 static void orion_spi_set_cs(struct spi_device *spi, bool enable)
 {
 	struct orion_spi *orion_spi;
+	int cs;
+
+	if (gpio_is_valid(spi->cs_gpio))
+		cs = 0;
+	else
+		cs = spi->chip_select;
 
 	orion_spi = spi_master_get_devdata(spi->master);
 
 	orion_spi_clrbits(orion_spi, ORION_SPI_IF_CTRL_REG, ORION_SPI_CS_MASK);
 	orion_spi_setbits(orion_spi, ORION_SPI_IF_CTRL_REG,
-				ORION_SPI_CS(spi->chip_select));
+				ORION_SPI_CS(cs));
 
 	/* Chip select logic is inverted from spi_set_cs */
 	if (!enable)
@@ -606,6 +613,7 @@ static int orion_spi_probe(struct platform_device *pdev)
 	master->setup = orion_spi_setup;
 	master->bits_per_word_mask = SPI_BPW_MASK(8) | SPI_BPW_MASK(16);
 	master->auto_runtime_pm = true;
+	master->flags = SPI_MASTER_GPIO_SS;
 
 	platform_set_drvdata(pdev, master);