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

commit dd8ecfcac66b4485416b2d1df0ec4798b198d7d6 upstream.

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>
Cc: "Petallo, MauriceX R" <mauricex.r.petallo@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/dma/TODO b/drivers/dma/TODO
index 734ed02..b8045cd 100644 (file)
--- 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 d585787..b0972b3 100644 (file)
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -680,17 +680,9 @@ 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);
 
@@ -1095,9 +1087,12 @@ 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)