| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.14 69/83] dma: edma: fix incorrect SG list handling | Date | Sun, 11 May 2014 21:20:10 +0200 |
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3.14-stable review patch. If anyone has any objections, please let me know.
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From: Sekhar Nori <nsekhar@ti.com>
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 <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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/dma/edma.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/drivers/dma/edma.c +++ b/drivers/dma/edma.c @@ -182,11 +182,13 @@ static void edma_execute(struct edma_cha 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); } /*
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