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    SubjectRe: [PATCH v2 2/2] dma/imx-sdma: add wmb before enable a channel
    On Sun, Jan 01, 2012 at 10:38:12PM +0800, Richard Zhao wrote:
    > dma_alloc_coherent memory may be bufferable. We need to add
    > nececcary memory barrier.
    >
    > Signed-off-by: Richard Zhao <richard.zhao@linaro.org>
    > ---
    > drivers/dma/imx-sdma.c | 1 +
    > 1 files changed, 1 insertions(+), 0 deletions(-)
    >
    > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
    > index f8e87b5..9301bff 100644
    > --- a/drivers/dma/imx-sdma.c
    > +++ b/drivers/dma/imx-sdma.c
    > @@ -394,6 +394,7 @@ static int sdma_config_ownership(struct sdma_channel *sdmac,
    >
    > static void sdma_enable_channel(struct sdma_engine *sdma, int channel)
    > {
    > + wmb();
    > __raw_writel(1 << channel, sdma->regs + SDMA_H_START);

    Use writel(). That's what it's there for:

    #ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE
    #define __iowmb() wmb()
    #endif
    #define writel_relaxed(v,c) ((void)__raw_writel((__force u32) \
    cpu_to_le32(v),__mem_pci(c)))
    #define writel(v,c) ({ __iowmb(); writel_relaxed(v,c); })


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