[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.

Mika,

I wonder if the spurious interrupts were the real problem behind what
was causing the Oops that prompted your patch:

dma/ep93xx_dma: prevent ep93xx_dma_tasklet() to reference an empty list

???

Hartley