fsldma: Fix the DMA halt when using DMA_INTERRUPT async_tx transfer.

The DMA_INTERRUPT async_tx is a NULL transfer, thus the BCR(count register)
is 0. When the transfer started with a byte count of zero, the DMA
controller will triger a PE(programming error) event and halt, not a normal
interrupt. I add special codes for PE event and DMA_INTERRUPT
async_tx testing.

Signed-off-by: Zhang Wei <wei.zhang@freescale.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

2 files changed, 31 insertions, 0 deletions

diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
index ad2f938597e2..72692309398a 100644
--- a/drivers/dma/fsldma.c
+++ b/drivers/dma/fsldma.c
@@ -123,6 +123,11 @@ static dma_addr_t get_ndar(struct fsl_dma_chan *fsl_chan)
         return DMA_IN(fsl_chan, &fsl_chan->reg_base->ndar, 64);
 }
 
+static u32 get_bcr(struct fsl_dma_chan *fsl_chan)
+{
+        return DMA_IN(fsl_chan, &fsl_chan->reg_base->bcr, 32);
+}
+
 static int dma_is_idle(struct fsl_dma_chan *fsl_chan)
 {
         u32 sr = get_sr(fsl_chan);
@@ -426,6 +431,9 @@ fsl_dma_prep_interrupt(struct dma_chan *chan)
         new->async_tx.cookie = -EBUSY;
         new->async_tx.ack = 0;
 
+        /* Insert the link descriptor to the LD ring */
+        list_add_tail(&new->node, &new->async_tx.tx_list);
+
         /* Set End-of-link to the last link descriptor of new list*/
         set_ld_eol(fsl_chan, new);
 
@@ -701,6 +709,23 @@ static irqreturn_t fsl_dma_chan_do_interrupt(int irq, void *data)
         if (stat & FSL_DMA_SR_TE)
                 dev_err(fsl_chan->dev, "Transfer Error!\n");
 
+        /* Programming Error
+         * The DMA_INTERRUPT async_tx is a NULL transfer, which will
+         * triger a PE interrupt.
+         */
+        if (stat & FSL_DMA_SR_PE) {
+                dev_dbg(fsl_chan->dev, "event: Programming Error INT\n");
+                if (get_bcr(fsl_chan) == 0) {
+                        /* BCR register is 0, this is a DMA_INTERRUPT async_tx.
+                         * Now, update the completed cookie, and continue the
+                         * next uncompleted transfer.
+                         */
+                        fsl_dma_update_completed_cookie(fsl_chan);
+                        fsl_chan_xfer_ld_queue(fsl_chan);
+                }
+                stat &= ~FSL_DMA_SR_PE;
+        }
+
         /* If the link descriptor segment transfer finishes,
          * we will recycle the used descriptor.
          */
@@ -841,6 +866,11 @@ static int fsl_dma_self_test(struct fsl_dma_chan *fsl_chan)
         tx3 = fsl_dma_prep_memcpy(chan, dma_dest, dma_src, test_size / 4, 0);
         async_tx_ack(tx3);
 
+        /* Interrupt tx test */
+        tx1 = fsl_dma_prep_interrupt(chan);
+        async_tx_ack(tx1);
+        cookie = fsl_dma_tx_submit(tx1);
+
         /* Test exchanging the prepared tx sort */
         cookie = fsl_dma_tx_submit(tx3);
         cookie = fsl_dma_tx_submit(tx2);
diff --git a/drivers/dma/fsldma.h b/drivers/dma/fsldma.h
index ba78c42121ba..fddd6aee2a63 100644
--- a/drivers/dma/fsldma.h
+++ b/drivers/dma/fsldma.h
@@ -40,6 +40,7 @@
 #define FSL_DMA_MR_EOTIE        0x00000080
 
 #define FSL_DMA_SR_CH           0x00000020
+#define FSL_DMA_SR_PE           0x00000010
 #define FSL_DMA_SR_CB           0x00000004
 #define FSL_DMA_SR_TE           0x00000080
 #define FSL_DMA_SR_EOSI         0x00000002