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    SubjectRe: [PATCH v3 2/2] dma/imx-sdma: use writel to write register when enable a channel
    On Thu, Jan 05, 2012 at 03:59:22PM +0800, Richard Zhao wrote:
    > dma_alloc_coherent memory may be bufferable when set
    > CONFIG_ARM_DMA_MEM_BUFFERABLE. We need to add nececcary
    > memory barrier. writel implicitly call wmb in such case.
    >
    > Signed-off-by: Richard Zhao <richard.zhao@linaro.org>
    > ---
    > drivers/dma/imx-sdma.c | 2 +-
    > 1 files changed, 1 insertions(+), 1 deletions(-)
    >
    > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
    > index c2bc4f1..e987468 100644
    > --- a/drivers/dma/imx-sdma.c
    > +++ b/drivers/dma/imx-sdma.c
    > @@ -396,7 +396,7 @@ static int sdma_config_ownership(struct sdma_channel *sdmac,
    >
    > static void sdma_enable_channel(struct sdma_engine *sdma, int channel)
    > {
    > - __raw_writel(1 << channel, sdma->regs + SDMA_H_START);
    > + writel(1 << channel, sdma->regs + SDMA_H_START);
    > }
    >

    As educated by Arnd, generally it's safer to use pair of readl/writel
    than __raw_readl/__raw_writel in driver. I'm wondering if it's a good
    opportunity for us to change the pair all over this driver.

    --
    Regards,
    Shawn


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