1 files changed, 91 insertions, 25 deletions

diff --git a/drivers/spi/pxa2xx_spi.c b/drivers/spi/pxa2xx_spi.c
index 34c7c9875681..d47d3636227f 100644
--- 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)       ((((u32)(x)) & 0x07) == 0)
+#define MAX_DMA_LEN             8191
 
 /*
  * for testing SSCR1 changes that require SSP restart, basically
@@ -144,7 +145,6 @@ struct driver_data {
         size_t tx_map_len;
         u8 n_bytes;
         u32 dma_width;
-        int cs_change;
         int (*write)(struct driver_data *drv_data);
         int (*read)(struct driver_data *drv_data);
         irqreturn_t (*transfer_handler)(struct driver_data *drv_data);
@@ -406,8 +406,45 @@ static void giveback(struct driver_data *drv_data)
                                         struct spi_transfer,
                                         transfer_list);
 
+        /* Delay if requested before any change in chip select */
+        if (last_transfer->delay_usecs)
+                udelay(last_transfer->delay_usecs);
+
+        /* Drop chip select UNLESS cs_change is true or we are returning
+         * a message with an error, or next message is for another chip
+         */
         if (!last_transfer->cs_change)
                 drv_data->cs_control(PXA2XX_CS_DEASSERT);
+        else {
+                struct spi_message *next_msg;
+
+                /* Holding of cs was hinted, but we need to make sure
+                 * the next message is for the same chip.  Don't waste
+                 * time with the following tests unless this was hinted.
+                 *
+                 * We cannot postpone this until pump_messages, because
+                 * after calling msg->complete (below) the driver that
+                 * sent the current message could be unloaded, which
+                 * could invalidate the cs_control() callback...
+                 */
+
+                /* get a pointer to the next message, if any */
+                spin_lock_irqsave(&drv_data->lock, flags);
+                if (list_empty(&drv_data->queue))
+                        next_msg = NULL;
+                else
+                        next_msg = list_entry(drv_data->queue.next,
+                                        struct spi_message, queue);
+                spin_unlock_irqrestore(&drv_data->lock, flags);
+
+                /* see if the next and current messages point
+                 * to the same chip
+                 */
+                if (next_msg && next_msg->spi != msg->spi)
+                        next_msg = NULL;
+                if (!next_msg || msg->state == ERROR_STATE)
+                        drv_data->cs_control(PXA2XX_CS_DEASSERT);
+        }
 
         msg->state = NULL;
         if (msg->complete)
@@ -490,10 +527,9 @@ static void dma_transfer_complete(struct driver_data *drv_data)
         msg->actual_length += drv_data->len -
                                 (drv_data->rx_end - drv_data->rx);
 
-        /* Release chip select if requested, transfer delays are
-         * handled in pump_transfers */
-        if (drv_data->cs_change)
-                drv_data->cs_control(PXA2XX_CS_DEASSERT);
+        /* Transfer delays and chip select release are
+         * handled in pump_transfers or giveback
+         */
 
         /* Move to next transfer */
         msg->state = next_transfer(drv_data);
@@ -602,10 +638,9 @@ static void int_transfer_complete(struct driver_data *drv_data)
         drv_data->cur_msg->actual_length += drv_data->len -
                                 (drv_data->rx_end - drv_data->rx);
 
-        /* Release chip select if requested, transfer delays are
-         * handled in pump_transfers */
-        if (drv_data->cs_change)
-                drv_data->cs_control(PXA2XX_CS_DEASSERT);
+        /* Transfer delays and chip select release are
+         * handled in pump_transfers or giveback
+         */
 
         /* Move to next transfer */
         drv_data->cur_msg->state = next_transfer(drv_data);
@@ -840,23 +875,40 @@ static void pump_transfers(unsigned long data)
                 return;
         }
 
-        /* Delay if requested at end of transfer*/
+        /* Delay if requested at end of transfer before CS change */
         if (message->state == RUNNING_STATE) {
                 previous = list_entry(transfer->transfer_list.prev,
                                         struct spi_transfer,
                                         transfer_list);
                 if (previous->delay_usecs)
                         udelay(previous->delay_usecs);
+
+                /* Drop chip select only if cs_change is requested */
+                if (previous->cs_change)
+                        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 %u 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 */
@@ -878,7 +930,6 @@ static void pump_transfers(unsigned long data)
         drv_data->len = transfer->len & DCMD_LENGTH;
         drv_data->write = drv_data->tx ? chip->write : null_writer;
         drv_data->read = drv_data->rx ? chip->read : null_reader;
-        drv_data->cs_change = transfer->cs_change;
 
         /* Change speed and bit per word on a per transfer */
         cr0 = chip->cr0;
@@ -925,7 +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");
                 }
@@ -939,8 +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;