[linux-yocto] [PATCH 08/28] dmaengine: dw: don't perform DMA when dmaengine_submit is called

[rebecca.swee.fun.chang at intel.com]

From: Andy Shevchenko <andriy.shevchenko at linux.intel.com>

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 at linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul at intel.com>
(cherry picked from commit dd8ecfcac66b4485416b2d1df0ec4798b198d7d6)
Signed-off-by: Chang Rebecca Swee Fun <rebecca.swee.fun.chang at intel.com>
---
 drivers/dma/TODO      |  1 -
 drivers/dma/dw/core.c | 19 +++++++------------
 2 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/drivers/dma/TODO b/drivers/dma/TODO
index 734ed02..b8045cd 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 4b03634..4e5a0f5 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -703,17 +703,9 @@ 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);
 
@@ -1119,9 +1111,12 @@ 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)
-- 
1.9.1