Re: [PATCH] dma: edma: fix incorrect SG list handling

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On Mon, 17 Mar 2014, Sekhar Nori wrote:

> Hi Jon,
> 
> On Monday 17 March 2014 06:28 PM, Jon Ringle wrote:
> > 
> > On Mon, 17 Mar 2014, Sekhar Nori wrote:
> > 
> >> 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@xxxxxxxxxxxxxxx> # v3.12.x+
> >> Cc: Joel Fernandes <joelf@xxxxxx>
> >> Reported-by: Jon Ringle <jringle@xxxxxxxxxxxxx>
> >> Signed-off-by: Sekhar Nori <nsekhar@xxxxxx>
> >> ---
> >> Jon, can you please confirm this fixes the issue you
> >> reported?
> > 
> > The patch does not apply on linux-3.12 due to changes to the 3 context 
> > lines at the start of the hunk.
> > 
> > But, I manually fixed up the code and it does fix the issue  on our AM1808 
> > board.
> 
> Thanks for the testing. The patch is meant for latest mainline but based
> on what you said, a manual backport to v3.12-stable will be required.
> 
> Can you please reply with a formal Tested-by: ?

Tested-by: Jon Ringle <jringle@xxxxxxxxxxxxx>
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