spi/xilinx: Support for spi mode LOOP

Hardware supports LOOP mode. Support it also in the driver.
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-xilinx.c

@@ -35,7 +35,7 @@
 #define XSPI_CR_CPOL		0x08
 #define XSPI_CR_CPHA		0x10
 #define XSPI_CR_MODE_MASK	(XSPI_CR_CPHA | XSPI_CR_CPOL | \
-				 XSPI_CR_LSB_FIRST)
+				 XSPI_CR_LSB_FIRST | XSPI_CR_LOOP)
 #define XSPI_CR_TXFIFO_RESET	0x20
 #define XSPI_CR_RXFIFO_RESET	0x40
 #define XSPI_CR_MANUAL_SSELECT	0x80
@@ -197,6 +197,8 @@ static void xilinx_spi_chipselect(struct spi_device *spi, int is_on)
 			cr |= XSPI_CR_CPOL;
 		if (spi->mode & SPI_LSB_FIRST)
 			cr |= XSPI_CR_LSB_FIRST;
+		if (spi->mode & SPI_LOOP)
+			cr |= XSPI_CR_LOOP;
 		xspi->write_fn(cr, xspi->regs + XSPI_CR_OFFSET);
 
 		/* We do not check spi->max_speed_hz here as the SPI clock
@@ -356,7 +358,7 @@ 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;
+	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST | SPI_LOOP;
 
 	xspi = spi_master_get_devdata(master);
 	xspi->bitbang.master = master;