spi/xilinx: Support for spi mode CS_HIGH

The core controls the chip select lines individually.

By default, all the lines are consider active_low. After
spi_setup_transfer, it has its real value.
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-xilinx.c

@@ -89,6 +89,7 @@ struct xilinx_spi {
 	int remaining_bytes;	/* the number of bytes left to transfer */
 	u8 bits_per_word;
 	int buffer_size;	/* buffer size in words */
+	u32 cs_inactive;	/* Level of the CS pins when inactive*/
 	unsigned int (*read_fn)(void __iomem *);
 	void (*write_fn)(u32, void __iomem *);
 	void (*tx_fn)(struct xilinx_spi *);
@@ -194,14 +195,17 @@ static void xspi_init_hw(struct xilinx_spi *xspi)
 static void xilinx_spi_chipselect(struct spi_device *spi, int is_on)
 {
 	struct xilinx_spi *xspi = spi_master_get_devdata(spi->master);
+	u16 cr;
+	u32 cs;
 
 	if (is_on == BITBANG_CS_INACTIVE) {
 		/* Deselect the slave on the SPI bus */
-		xspi->write_fn(0xffff, xspi->regs + XSPI_SSR_OFFSET);
-	} else if (is_on == BITBANG_CS_ACTIVE) {
+		xspi->write_fn(xspi->cs_inactive, xspi->regs + XSPI_SSR_OFFSET);
+		return;
+	}
+
 	/* Set the SPI clock phase and polarity */
-		u16 cr = xspi->read_fn(xspi->regs + XSPI_CR_OFFSET)
-			 & ~XSPI_CR_MODE_MASK;
+	cr = xspi->read_fn(xspi->regs + XSPI_CR_OFFSET)	& ~XSPI_CR_MODE_MASK;
 	if (spi->mode & SPI_CPHA)
 		cr |= XSPI_CR_CPHA;
 	if (spi->mode & SPI_CPOL)
@@ -217,10 +221,11 @@ static void xilinx_spi_chipselect(struct spi_device *spi, int is_on)
 	 * parameter)
 	 */
 
+	cs = xspi->cs_inactive;
+	cs ^= BIT(spi->chip_select);
+
 	/* Activate the chip select */
-		xspi->write_fn(~(0x0001 << spi->chip_select),
-			xspi->regs + XSPI_SSR_OFFSET);
-	}
+	xspi->write_fn(cs, xspi->regs + XSPI_SSR_OFFSET);
 }
 
 /* spi_bitbang requires custom setup_transfer() to be defined if there is a
@@ -229,6 +234,13 @@ static void xilinx_spi_chipselect(struct spi_device *spi, int is_on)
 static int xilinx_spi_setup_transfer(struct spi_device *spi,
 		struct spi_transfer *t)
 {
+	struct xilinx_spi *xspi = spi_master_get_devdata(spi->master);
+
+	if (spi->mode & SPI_CS_HIGH)
+		xspi->cs_inactive &= ~BIT(spi->chip_select);
+	else
+		xspi->cs_inactive |= BIT(spi->chip_select);
+
 	return 0;
 }
 
@@ -376,9 +388,11 @@ static int xilinx_spi_probe(struct platform_device *pdev)
 		return -ENODEV;
 
 	/* the spi->mode bits understood by this driver: */
-	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST | SPI_LOOP;
+	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST | SPI_LOOP |
+			    SPI_CS_HIGH;
 
 	xspi = spi_master_get_devdata(master);
+	xspi->cs_inactive = 0xffffffff;
 	xspi->bitbang.master = master;
 	xspi->bitbang.chipselect = xilinx_spi_chipselect;
 	xspi->bitbang.setup_transfer = xilinx_spi_setup_transfer;