spi/pxa2xx: enable DMA on newer Intel LPSS silicon

There is an additional bit in the Intel LPSS SPI private registers that
needs to be set in order to be able to use DMA with the SPI controller.
Enable this as well.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/spi/spi-pxa2xx.c

@@ -69,6 +69,8 @@ MODULE_ALIAS("platform:pxa2xx-spi");
 #define LPSS_TX_HITHRESH_DFLT	224
 
 /* Offset from drv_data->lpss_base */
+#define GENERAL_REG		0x08
+#define GENERAL_REG_RXTO_HOLDOFF_DISABLE BIT(24)
 #define SSP_REG			0x0c
 #define SPI_CS_CONTROL		0x18
 #define SPI_CS_CONTROL_SW_MODE	BIT(0)
@@ -142,8 +144,13 @@ detection_done:
 	__lpss_ssp_write_priv(drv_data, SPI_CS_CONTROL, value);
 
 	/* Enable multiblock DMA transfers */
-	if (drv_data->master_info->enable_dma)
+	if (drv_data->master_info->enable_dma) {
 		__lpss_ssp_write_priv(drv_data, SSP_REG, 1);
+
+		value = __lpss_ssp_read_priv(drv_data, GENERAL_REG);
+		value |= GENERAL_REG_RXTO_HOLDOFF_DISABLE;
+		__lpss_ssp_write_priv(drv_data, GENERAL_REG, value);
+	}
 }
 
 static void lpss_ssp_cs_control(struct driver_data *drv_data, bool enable)