This is a note to let you know that I've just added the patch titled
dma: edma: fix incorrect SG list handling
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dma-edma-fix-incorrect-sg-list-handling.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 5fc68a6cad658e45dca3e0a6607df3a8e5df4ef9 Mon Sep 17 00:00:00 2001
From: Sekhar Nori <[email protected]>
Date: Wed, 19 Mar 2014 11:25:50 +0530
Subject: dma: edma: fix incorrect SG list handling
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: Greg Kroah-Hartman <[email protected]>
---
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);
}
/*
Patches currently in stable-queue which might be from [email protected] are
queue-3.14/dma-edma-fix-incorrect-sg-list-handling.patch
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