From 4d22eb083cf667129e9158b407dda5588c89c64a Mon Sep 17 00:00:00 2001 From: Sekhar Nori Date: Wed, 19 Mar 2014 11:25:50 +0530 Subject: [PATCH] dma: edma: fix incorrect SG list handling commit 5fc68a6cad658e45dca3e0a6607df3a8e5df4ef9 upstream. 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: Joel Fernandes Acked-by: Joel Fernandes Tested-by: Jon Ringle Tested-by: Alexander Holler Reported-by: Jon Ringle Signed-off-by: Sekhar Nori Signed-off-by: Vinod Koul Signed-off-by: Jiri Slaby --- drivers/dma/edma.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c index 10b577fcf48d8..0ad40e4a7ae06 100644 --- a/drivers/dma/edma.c +++ b/drivers/dma/edma.c @@ -170,11 +170,13 @@ static void edma_execute(struct edma_chan *echan) if (edesc->processed == edesc->pset_nr) edma_link(echan->slot[nslots-1], 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); } /*