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    SubjectRE: [PATCH] ep93xx: Implement double buffering for M2M DMA channels
    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@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@visionengravers.com>
    >
    > Tested-by: Mika Westerberg <mika.westerberg@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



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