From: Richard Zhao <richard.zhao@freescale.com>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Richard Zhao <richard.zhao@linaro.org>, <patches@linaro.org>,
<vinod.koul@intel.com>, <linux-kernel@vger.kernel.org>,
<eric.miao@linaro.org>, <kernel@pengutronix.de>,
<dan.j.williams@intel.com>, <shawn.guo@linaro.org>,
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 2/2] dma/imx-sdma: add wmb before enable a channel
Date: Wed, 4 Jan 2012 10:31:58 +0800 [thread overview]
Message-ID: <20120104023157.GJ2414@b20223-02.ap.freescale.net> (raw)
In-Reply-To: <20120103174639.GF2914@n2100.arm.linux.org.uk>
On Tue, Jan 03, 2012 at 05:46:39PM +0000, Russell King - ARM Linux wrote:
> 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); })
Why does writel always call wmb? ioremap memory needs mb too?
Isn't it supposed to be when there's prior touch of dma memory?
Thanks
Richard
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
next prev parent reply other threads:[~2012-01-04 2:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-01 14:38 [PATCH v2 0/2] imx-sdma: memory barrier fix Richard Zhao
2012-01-01 14:38 ` [PATCH v2 1/2] dma/imx-sdma: let sdma_run_channel call sdma_enable_channel Richard Zhao
2012-01-01 14:38 ` [PATCH v2 2/2] dma/imx-sdma: add wmb before enable a channel Richard Zhao
2012-01-03 17:46 ` Russell King - ARM Linux
2012-01-04 2:31 ` Richard Zhao [this message]
2012-01-05 1:56 ` Richard Zhao
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