Messages in this thread | | | Date | Thu, 5 Jan 2012 17:19:05 +0800 | From | Richard Zhao <> | Subject | Re: [PATCH v3 2/2] dma/imx-sdma: use writel to write register when enable a channel |
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Hi Shawn,
On Thu, Jan 05, 2012 at 05:23:17PM +0800, Shawn Guo wrote: > 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. Russel mentioned that too. But I cannot understand. If CONFIG_ARM_DMA_MEM_BUFFERABLE, readl/writel always call rmb/wmb. Do we realy need it? It might affect performance.
Du to the concern, I didn't convert all the readl/writel.
Thanks Richard > > -- > Regards, > Shawn > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
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