Re: [PATCH] dma/imx-sdma: add wmb before enable/run a channel

From: Richard Zhao
Date: Sun Jan 01 2012 - 08:30:38 EST


On Sun, Jan 01, 2012 at 08:14:25AM +0100, Uwe Kleine-König wrote:
> Hello Richard,
>
> On Sun, Jan 01, 2012 at 11:27:40AM +0800, Richard Zhao wrote:
> > dma_alloc_coherent memory may be bufferable. We need to add
> > nececcary memory barrier.
> necessary
>
> >
> > Signed-off-by: Richard Zhao <richard.zhao@xxxxxxxxxx>
> > ---
> > drivers/dma/imx-sdma.c | 2 ++
> > 1 files changed, 2 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> > index 2ebb2bc..8cd9492 100644
> > --- a/drivers/dma/imx-sdma.c
> > +++ b/drivers/dma/imx-sdma.c
> > @@ -403,6 +403,7 @@ static int sdma_run_channel(struct sdma_channel *sdmac)
> >
> > init_completion(&sdmac->done);
> >
> > + wmb();
> > __raw_writel(1 << channel, sdma->regs + SDMA_H_START);
> >
> > ret = wait_for_completion_timeout(&sdmac->done, HZ);
> > @@ -809,6 +810,7 @@ out:
> >
> > static void sdma_enable_channel(struct sdma_engine *sdma, int channel)
> > {
> > + wmb();
> > __raw_writel(1 << channel, sdma->regs + SDMA_H_START);
> > }
> I don't know the sdma code very well, but wouldn't it be nice to call
> sdma_enable_channel() in sdma_run_channel() instead of open coding it?
right.
>
> As you probably need some rearrangements to have sdma_enable_channel()
> declared in sdma_run_channel() this might be better done with a seperate
> patch.
It'll save one wmb.

Thanks
Richard
>
> Best regards
> Uwe
>
> --
> Pengutronix e.K. | Uwe Kleine-König |
> Industrial Linux Solutions | http://www.pengutronix.de/ |
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