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authorSekhar Nori <nsekhar@ti.com>2014-03-19 11:25:50 +0530
committerVinod Koul <vinod.koul@intel.com>2014-04-14 09:29:55 +0530
commit5fc68a6cad658e45dca3e0a6607df3a8e5df4ef9 (patch)
treeab4dc89221cfeb0f7cf7c6c3551b5e2856bef6cf /drivers/dma
parentc9eaa447e77efe77b7fa4c953bd62de8297fd6c5 (diff)
dma: edma: fix incorrect SG list handling
The code to handle any length SG lists calls edma_resume() even before edma_start() is called. This is incorrect because edma_resume() enables edma events on the channel after which CPU (in edma_start) cannot clear posted events by writing to ECR (per the EDMA user's guide). Because of this EDMA transfers fail to start if due to some reason there is a pending EDMA event registered even before EDMA transfers are started. This can happen if an EDMA event is a byproduct of device initialization. Fix this by calling edma_resume() only if it is not the first batch of MAX_NR_SG elements. Without this patch, MMC/SD fails to function on DA850 EVM with DMA. The behaviour is triggered by specific IP and this can explain why the issue was not reported before (example with MMC/SD on AM335x). Tested on DA850 EVM and AM335x EVM-SK using MMC/SD card. Cc: stable@vger.kernel.org # v3.12.x+ Cc: Joel Fernandes <joelf@ti.com> Acked-by: Joel Fernandes <joelf@ti.com> Tested-by: Jon Ringle <jringle@gridpoint.com> Tested-by: Alexander Holler <holler@ahsoftware.de> Reported-by: Jon Ringle <jringle@gridpoint.com> Signed-off-by: Sekhar Nori <nsekhar@ti.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Diffstat (limited to 'drivers/dma')
-rw-r--r--drivers/dma/edma.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c
index cd04eb7b182e..926360c2db6a 100644
--- a/drivers/dma/edma.c
+++ b/drivers/dma/edma.c
@@ -182,11 +182,13 @@ static void edma_execute(struct edma_chan *echan)
echan->ecc->dummy_slot);
}
- edma_resume(echan->ch_num);
-
if (edesc->processed <= MAX_NR_SG) {
dev_dbg(dev, "first transfer starting %d\n", echan->ch_num);
edma_start(echan->ch_num);
+ } else {
+ dev_dbg(dev, "chan: %d: completed %d elements, resuming\n",
+ echan->ch_num, edesc->processed);
+ edma_resume(echan->ch_num);
}
/*