pxa2xx_spi: dma bugfixes

[pandora-kernel.git] / drivers / spi / pxa2xx_spi.c

diff --git a/drivers/spi/pxa2xx_spi.c b/drivers/spi/pxa2xx_spi.c
index a7b9070..0e53354 100644 (file)
--- a/drivers/spi/pxa2xx_spi.c
+++ b/drivers/spi/pxa2xx_spi.c
@@ -47,9 +47,10 @@ MODULE_ALIAS("platform:pxa2xx-spi");
 
 #define MAX_BUSES 3
 
-#define DMA_INT_MASK (DCSR_ENDINTR | DCSR_STARTINTR | DCSR_BUSERR)
-#define RESET_DMA_CHANNEL (DCSR_NODESC | DMA_INT_MASK)
-#define IS_DMA_ALIGNED(x) (((u32)(x)&0x07)==0)
+#define DMA_INT_MASK           (DCSR_ENDINTR | DCSR_STARTINTR | DCSR_BUSERR)
+#define RESET_DMA_CHANNEL      (DCSR_NODESC | DMA_INT_MASK)
+#define IS_DMA_ALIGNED(x)      (((x) & 0x07) == 0)
+#define MAX_DMA_LEN            8191
 
 /*
  * for testing SSCR1 changes that require SSP restart, basically
@@ -887,14 +888,27 @@ static void pump_transfers(unsigned long data)
                        drv_data->cs_control(PXA2XX_CS_DEASSERT);
        }
 
-       /* Check transfer length */
-       if (transfer->len > 8191)
-       {
-               dev_warn(&drv_data->pdev->dev, "pump_transfers: transfer "
-                               "length greater than 8191\n");
-               message->status = -EINVAL;
-               giveback(drv_data);
-               return;
+       /* Check for transfers that need multiple DMA segments */
+       if (transfer->len > MAX_DMA_LEN && chip->enable_dma) {
+
+               /* reject already-mapped transfers; PIO won't always work */
+               if (message->is_dma_mapped
+                               || transfer->rx_dma || transfer->tx_dma) {
+                       dev_err(&drv_data->pdev->dev,
+                               "pump_transfers: mapped transfer length "
+                               "of %lu is greater than %d\n",
+                               transfer->len, MAX_DMA_LEN);
+                       message->status = -EINVAL;
+                       giveback(drv_data);
+                       return;
+               }
+
+               /* warn ... we force this to PIO mode */
+               if (printk_ratelimit())
+                       dev_warn(&message->spi->dev, "pump_transfers: "
+                               "DMA disabled for transfer length %ld "
+                               "greater than %d\n",
+                               (long)drv_data->len, MAX_DMA_LEN);
        }
 
        /* Setup the transfer state based on the type of transfer */
@@ -962,7 +976,7 @@ static void pump_transfers(unsigned long data)
                                                        &dma_thresh))
                                if (printk_ratelimit())
                                        dev_warn(&message->spi->dev,
-                                               "pump_transfer: "
+                                               "pump_transfers: "
                                                "DMA burst size reduced to "
                                                "match bits_per_word\n");
                }
@@ -976,8 +990,23 @@ static void pump_transfers(unsigned long data)
 
        message->state = RUNNING_STATE;
 
-       /* Try to map dma buffer and do a dma transfer if successful */
-       if ((drv_data->dma_mapped = map_dma_buffers(drv_data))) {
+       /* Try to map dma buffer and do a dma transfer if successful, but
+        * only if the length is non-zero and less than MAX_DMA_LEN.
+        *
+        * Zero-length non-descriptor DMA is illegal on PXA2xx; force use
+        * of PIO instead.  Care is needed above because the transfer may
+        * have have been passed with buffers that are already dma mapped.
+        * A zero-length transfer in PIO mode will not try to write/read
+        * to/from the buffers
+        *
+        * REVISIT large transfers are exactly where we most want to be
+        * using DMA.  If this happens much, split those transfers into
+        * multiple DMA segments rather than forcing PIO.
+        */
+       drv_data->dma_mapped = 0;
+       if (drv_data->len > 0 && drv_data->len <= MAX_DMA_LEN)
+               drv_data->dma_mapped = map_dma_buffers(drv_data);
+       if (drv_data->dma_mapped) {
 
                /* Ensure we have the correct interrupt handler */
                drv_data->transfer_handler = dma_transfer;