spi: rockchip: Support cs-gpio

1.Add standard cs-gpio support
2.Refer to spi-controller.yaml for details

Signed-off-by: Jon Lin <jon.lin@rock-chips.com>
Link: https://lore.kernel.org/r/20210621104848.19539-1-jon.lin@rock-chips.com
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-rockchip.c

@@ -157,7 +157,8 @@
  */
 #define ROCKCHIP_SPI_MAX_TRANLEN		0xffff
 
-#define ROCKCHIP_SPI_MAX_CS_NUM			2
+/* 2 for native cs, 2 for cs-gpio */
+#define ROCKCHIP_SPI_MAX_CS_NUM			4
 #define ROCKCHIP_SPI_VER2_TYPE1			0x05EC0002
 #define ROCKCHIP_SPI_VER2_TYPE2			0x00110002
 
@@ -245,11 +246,15 @@ static void rockchip_spi_set_cs(struct spi_device *spi, bool enable)
 		/* Keep things powered as long as CS is asserted */
 		pm_runtime_get_sync(rs->dev);
 
-		ROCKCHIP_SPI_SET_BITS(rs->regs + ROCKCHIP_SPI_SER,
-				      BIT(spi->chip_select));
+		if (spi->cs_gpiod)
+			ROCKCHIP_SPI_SET_BITS(rs->regs + ROCKCHIP_SPI_SER, 1);
+		else
+			ROCKCHIP_SPI_SET_BITS(rs->regs + ROCKCHIP_SPI_SER, BIT(spi->chip_select));
 	} else {
-		ROCKCHIP_SPI_CLR_BITS(rs->regs + ROCKCHIP_SPI_SER,
-				      BIT(spi->chip_select));
+		if (spi->cs_gpiod)
+			ROCKCHIP_SPI_CLR_BITS(rs->regs + ROCKCHIP_SPI_SER, 1);
+		else
+			ROCKCHIP_SPI_CLR_BITS(rs->regs + ROCKCHIP_SPI_SER, BIT(spi->chip_select));
 
 		/* Drop reference from when we first asserted CS */
 		pm_runtime_put(rs->dev);