3.13.11.3 -stable review patch. If anyone has any objections, please let me know.
------------------ From: Sekhar Nori <[email protected]> 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 <[email protected]> Acked-by: Joel Fernandes <[email protected]> Tested-by: Jon Ringle <[email protected]> Tested-by: Alexander Holler <[email protected]> Reported-by: Jon Ringle <[email protected]> Signed-off-by: Sekhar Nori <[email protected]> Signed-off-by: Vinod Koul <[email protected]> Signed-off-by: Kamal Mostafa <[email protected]> --- 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 2539ea0..037443c 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); } /* -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
