1 files changed, 42 insertions, 28 deletions

diff --git a/drivers/spi/davinci_spi.c b/drivers/spi/davinci_spi.c
index f5129390bc2d..705d0069bce0 100644
--- a/drivers/spi/davinci_spi.c
+++ b/drivers/spi/davinci_spi.c
@@ -138,6 +138,8 @@ struct davinci_spi {
 
         const void              *tx;
         void                    *rx;
+#define SPI_TMP_BUFSZ   (SMP_CACHE_BYTES + 1)
+        u8                      rx_tmp_buf[SPI_TMP_BUFSZ];
         int                     rcount;
         int                     wcount;
         struct davinci_spi_dma  dma_channels;
@@ -716,10 +718,12 @@ static int davinci_spi_bufs_dma(struct spi_device *spi, struct spi_transfer *t)
         struct davinci_spi *davinci_spi;
         int int_status = 0;
         int count;
+        unsigned rx_buf_count;
         struct davinci_spi_dma *davinci_spi_dma;
         int data_type, ret;
         unsigned long tx_reg, rx_reg;
         struct davinci_spi_platform_data *pdata;
+        void *rx_buf;
         struct device *sdev;
 
         davinci_spi = spi_master_get_devdata(spi->master);
@@ -778,50 +782,60 @@ static int davinci_spi_bufs_dma(struct spi_device *spi, struct spi_transfer *t)
                         t->tx_buf ? data_type : 0, 0);
         edma_set_dest_index(davinci_spi_dma->dma_tx_channel, 0, 0);
 
+        /*
+         * Receive DMA setup
+         *
+         * If there is receive buffer, use it to receive data. If there
+         * is none provided, use a temporary receive buffer. Set the
+         * destination B index to 0 so effectively only one byte is used
+         * in the temporary buffer (address does not increment).
+         *
+         * The source of receive data is the receive data register. The
+         * source address never increments.
+         */
+
         if (t->rx_buf) {
-                t->rx_dma = dma_map_single(&spi->dev, (void *)t->rx_buf, count,
-                                DMA_FROM_DEVICE);
-                if (dma_mapping_error(&spi->dev, t->rx_dma)) {
-                        dev_dbg(sdev, "Couldn't DMA map a %d bytes RX buffer\n",
-                                        count);
-                        if (t->tx_buf != NULL)
-                                dma_unmap_single(NULL, t->tx_dma,
-                                                 count, DMA_TO_DEVICE);
-                        return -ENOMEM;
-                }
-                edma_set_transfer_params(davinci_spi_dma->dma_rx_channel,
-                                data_type, count, 1, 0, ASYNC);
-                edma_set_src(davinci_spi_dma->dma_rx_channel,
-                                rx_reg, INCR, W8BIT);
-                edma_set_dest(davinci_spi_dma->dma_rx_channel,
-                                t->rx_dma, INCR, W8BIT);
-                edma_set_src_index(davinci_spi_dma->dma_rx_channel, 0, 0);
-                edma_set_dest_index(davinci_spi_dma->dma_rx_channel,
-                                data_type, 0);
+                rx_buf = t->rx_buf;
+                rx_buf_count = count;
+        } else {
+                rx_buf = davinci_spi->rx_tmp_buf;
+                rx_buf_count = sizeof(davinci_spi->rx_tmp_buf);
+        }
+
+        t->rx_dma = dma_map_single(&spi->dev, rx_buf, rx_buf_count,
+                                                        DMA_FROM_DEVICE);
+        if (dma_mapping_error(&spi->dev, t->rx_dma)) {
+                dev_dbg(sdev, "Couldn't DMA map a %d bytes RX buffer\n",
+                                                                rx_buf_count);
+                if (t->tx_buf)
+                        dma_unmap_single(NULL, t->tx_dma, count, DMA_TO_DEVICE);
+                return -ENOMEM;
         }
 
+        edma_set_transfer_params(davinci_spi_dma->dma_rx_channel, data_type,
+                                                        count, 1, 0, ASYNC);
+        edma_set_src(davinci_spi_dma->dma_rx_channel, rx_reg, INCR, W8BIT);
+        edma_set_dest(davinci_spi_dma->dma_rx_channel, t->rx_dma, INCR, W8BIT);
+        edma_set_src_index(davinci_spi_dma->dma_rx_channel, 0, 0);
+        edma_set_dest_index(davinci_spi_dma->dma_rx_channel,
+                                                t->rx_buf ? data_type : 0, 0);
+
         if (pdata->cshold_bug) {
                 u16 spidat1 = ioread16(davinci_spi->base + SPIDAT1 + 2);
                 iowrite16(spidat1, davinci_spi->base + SPIDAT1 + 2);
         }
 
-        if (t->rx_buf)
-                edma_start(davinci_spi_dma->dma_rx_channel);
-
+        edma_start(davinci_spi_dma->dma_rx_channel);
         edma_start(davinci_spi_dma->dma_tx_channel);
         davinci_spi_set_dma_req(spi, 1);
 
         wait_for_completion_interruptible(&davinci_spi_dma->dma_tx_completion);
-
-        if (t->rx_buf)
-                wait_for_completion_interruptible(
-                                &davinci_spi_dma->dma_rx_completion);
+        wait_for_completion_interruptible(&davinci_spi_dma->dma_rx_completion);
 
         if (t->tx_buf)
                 dma_unmap_single(NULL, t->tx_dma, count, DMA_TO_DEVICE);
 
-        if (t->rx_buf)
-                dma_unmap_single(NULL, t->rx_dma, count, DMA_FROM_DEVICE);
+        dma_unmap_single(NULL, t->rx_dma, rx_buf_count, DMA_FROM_DEVICE);
 
         /*
          * Check for bit error, desync error,parity error,timeout error and