[PATCH] ep93xx: Implement double buffering for M2M DMA channels

[H Hartley Sweeten]

On Thursday, March 22, 2012 1:04 PM, Mika Westerberg wrote:
> On Thu, Mar 22, 2012 at 01:52:52PM -0500, H Hartley Sweeten wrote:
>
>> I hacked this back to the handle_one_vic function. It looks like every time
>> I get the message above the stat read in that function shows an active
>> interrupt for DMAM2M0 (the dma rx channel) and DMAM2M1 (the dma
>> tx channel). Because of the way handle_one_vic processes the irq's, the
>> DMAM2M0 interrupt gets handled first. When it's done it must be clearing
>> the DMAM2M1 interrupt automatically for some reason. So, when it's
>> handled there is no interrupt pending so we get the message.
>> 
>> The "cleanest" fix I can think of is the following patch.  This is against
>> linux-next.
>
> I can't figure out any better fix unless we move ep93xx back to use
> !MULTI_IRQ_HANDLER which obviously is not good thing to do.

I agree.

>> From: H Hartley Sweeten <hsweeten at visionengravers.com>
>> 
>> dma: ep93xx: check for spurious interrupts
>> 
>> The ep93xx dma controller generates spurious interrupts on dma1chan1 when
>> used with the mmc_spi driver. Catch these early by making sure there is an
>> interrupt to actually process.
>> 
>> Signed-off-by: H Hartley Sweeten <hsweeten at visionengravers.com>
>
> Tested-by: Mika Westerberg <mika.westerberg at iki.fi>
>
> Thanks for investigating this. You missed one thing though, see below.
> Otherwise it doesn't compile :)
>
> diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
> index e1cc87a..614bff4 100644
> --- a/drivers/dma/ep93xx_dma.c
> +++ b/drivers/dma/ep93xx_dma.c
> @@ -751,7 +751,7 @@ static irqreturn_t ep93xx_dma_interrupt(int irq, void *dev_id)
> 		return IRQ_NONE;
>  	}
>  
> -	switch (edmac->edma->hw_interrupt(edmac)) {
> +	switch (edmac->edma->hw_interrupt(edmac, irq_status)) {
> 	case INTERRUPT_DONE:
> 		desc->complete = true;
> 		tasklet_schedule(&edmac->tasklet);

Gah... Misstyped it when I created the patch.

I'll fix it and post a proper patch with your Tested-by.

Thanks,
Hartley