spi/pxa2xx: add support for SPI_LOOP

This is useful when testing the functionality of the controller from userspace
and there aren't any real SPI slave devices connected to the bus.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Tested-by: Lu Cao <lucao@marvell.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/spi/spi-pxa2xx.c

@@ -846,6 +846,9 @@ static int setup(struct spi_device *spi)
 	chip->cr1 |= (((spi->mode & SPI_CPHA) != 0) ? SSCR1_SPH : 0)
 			| (((spi->mode & SPI_CPOL) != 0) ? SSCR1_SPO : 0);
 
+	if (spi->mode & SPI_LOOP)
+		chip->cr1 |= SSCR1_LBM;
+
 	/* NOTE:  PXA25x_SSP _could_ use external clocking ... */
 	if (!pxa25x_ssp_comp(drv_data))
 		dev_dbg(&spi->dev, "%ld Hz actual, %s\n",
@@ -939,7 +942,7 @@ static int pxa2xx_spi_probe(struct platform_device *pdev)
 	master->dev.parent = &pdev->dev;
 	master->dev.of_node = pdev->dev.of_node;
 	/* the spi->mode bits understood by this driver: */
-	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
+	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_LOOP;
 
 	master->bus_num = ssp->port_id;
 	master->num_chipselect = platform_info->num_chipselect;