dmaengine: dw: don't perform DMA when dmaengine_submit is called

Accordingly to discussion [1] and followed up documentation the DMA controller
driver shouldn't start any DMA operations when dmaengine_submit() is called.

This patch fixes the workflow in dw_dmac driver to follow the documentation.

[1] http://www.spinics.net/lists/arm-kernel/msg125987.html

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

2 files changed, 7 insertions, 13 deletions

diff --git a/drivers/dma/TODO b/drivers/dma/TODO
index 734ed0206cd5..b8045cd42ee1 100644
--- a/drivers/dma/TODO
+++ b/drivers/dma/TODO
@@ -7,7 +7,6 @@ TODO for slave dma
         - imx-dma
         - imx-sdma
         - mxs-dma.c
-        - dw_dmac
         - intel_mid_dma
 4. Check other subsystems for dma drivers and merge/move to dmaengine
 5. Remove dma_slave_config's dma direction.
diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index 52815b905b7c..1af731b83b3f 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -684,17 +684,9 @@ static dma_cookie_t dwc_tx_submit(struct dma_async_tx_descriptor *tx)
          * possible, perhaps even appending to those already submitted
          * for DMA. But this is hard to do in a race-free manner.
          */
-        if (list_empty(&dwc->active_list)) {
-                dev_vdbg(chan2dev(tx->chan), "%s: started %u\n", __func__,
-                                desc->txd.cookie);
-                list_add_tail(&desc->desc_node, &dwc->active_list);
-                dwc_dostart(dwc, dwc_first_active(dwc));
-        } else {
-                dev_vdbg(chan2dev(tx->chan), "%s: queued %u\n", __func__,
-                                desc->txd.cookie);
 
-                list_add_tail(&desc->desc_node, &dwc->queue);
-        }
+        dev_vdbg(chan2dev(tx->chan), "%s: queued %u\n", __func__, desc->txd.cookie);
+        list_add_tail(&desc->desc_node, &dwc->queue);
 
         spin_unlock_irqrestore(&dwc->lock, flags);
 
@@ -1099,9 +1091,12 @@ dwc_tx_status(struct dma_chan *chan,
 static void dwc_issue_pending(struct dma_chan *chan)
 {
         struct dw_dma_chan      *dwc = to_dw_dma_chan(chan);
+        unsigned long           flags;
 
-        if (!list_empty(&dwc->queue))
-                dwc_scan_descriptors(to_dw_dma(chan->device), dwc);
+        spin_lock_irqsave(&dwc->lock, flags);
+        if (list_empty(&dwc->active_list))
+                dwc_dostart_first_queued(dwc);
+        spin_unlock_irqrestore(&dwc->lock, flags);
 }
 
 static int dwc_alloc_chan_resources(struct dma_chan *chan)