spi_imx: full duplex dma corruption bugfix

Fix unsafe order in dma mapping operation: always flush data from the
cache *BEFORE* invalidating it, to allow full duplex transfers where the
same buffer may be used for both writes and reads.

Signed-off-by: Andrea Paterniani <a.paterniani@swapp-eng.it>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 22 insertions, 23 deletions

diff --git a/drivers/spi/spi_imx.c b/drivers/spi/spi_imx.c
index 61ba147e384d..0b4db0ce78d6 100644
--- a/drivers/spi/spi_imx.c
+++ b/drivers/spi/spi_imx.c
@@ -506,20 +506,6 @@ static int map_dma_buffers(struct driver_data *drv_data)
         if (!IS_DMA_ALIGNED(drv_data->rx) || !IS_DMA_ALIGNED(drv_data->tx))
                 return -1;
 
-        /* NULL rx means write-only transfer and no map needed
-           since rx DMA will not be used */
-        if (drv_data->rx) {
-                buf = drv_data->rx;
-                drv_data->rx_dma = dma_map_single(
-                                        dev,
-                                        buf,
-                                        drv_data->len,
-                                        DMA_FROM_DEVICE);
-                if (dma_mapping_error(dev, drv_data->rx_dma))
-                        return -1;
-                drv_data->rx_dma_needs_unmap = 1;
-        }
-
         if (drv_data->tx == NULL) {
                 /* Read only message --> use drv_data->dummy_dma_buf for dummy
                    writes to achive reads */
@@ -533,18 +519,31 @@ static int map_dma_buffers(struct driver_data *drv_data)
                                         buf,
                                         drv_data->tx_map_len,
                                         DMA_TO_DEVICE);
-        if (dma_mapping_error(dev, drv_data->tx_dma)) {
-                if (drv_data->rx_dma) {
-                        dma_unmap_single(dev,
-                                        drv_data->rx_dma,
-                                        drv_data->len,
-                                        DMA_FROM_DEVICE);
-                        drv_data->rx_dma_needs_unmap = 0;
-                }
+        if (dma_mapping_error(dev, drv_data->tx_dma))
                 return -1;
-        }
         drv_data->tx_dma_needs_unmap = 1;
 
+        /* NULL rx means write-only transfer and no map needed
+         * since rx DMA will not be used */
+        if (drv_data->rx) {
+                buf = drv_data->rx;
+                drv_data->rx_dma = dma_map_single(dev,
+                                                buf,
+                                                drv_data->len,
+                                                DMA_FROM_DEVICE);
+                if (dma_mapping_error(dev, drv_data->rx_dma)) {
+                        if (drv_data->tx_dma) {
+                                dma_unmap_single(dev,
+                                                drv_data->tx_dma,
+                                                drv_data->tx_map_len,
+                                                DMA_TO_DEVICE);
+                                drv_data->tx_dma_needs_unmap = 0;
+                        }
+                        return -1;
+                }
+                drv_data->rx_dma_needs_unmap = 1;
+        }
+
         return 0;
 }