From: Richard Zhao <richard.zhao@freescale.com>
To: Shawn Guo <shawn.guo@linaro.org>
Cc: Richard Zhao <richard.zhao@linaro.org>,
Arnd Bergmann <arnd@arndb.de>, <patches@linaro.org>,
<vinod.koul@intel.com>, <linux-kernel@vger.kernel.org>,
<eric.miao@linaro.org>, <kernel@pengutronix.de>,
<dan.j.williams@intel.com>,
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v3 2/2] dma/imx-sdma: use writel to write register when enable a channel
Date: Thu, 5 Jan 2012 17:19:05 +0800 [thread overview]
Message-ID: <20120105091904.GO2414@b20223-02.ap.freescale.net> (raw)
In-Reply-To: <20120105092316.GB1729@S2101-09.ap.freescale.net>
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
>
next prev parent reply other threads:[~2012-01-05 9:19 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-05 7:59 [PATCH v3 0/2] imx-sdma: memory barrier fix Richard Zhao
2012-01-05 7:59 ` [PATCH v3 1/2] dma/imx-sdma: let sdma_run_channel call sdma_enable_channel Richard Zhao
2012-01-05 9:14 ` Shawn Guo
2012-01-05 7:59 ` [PATCH v3 2/2] dma/imx-sdma: use writel to write register when enable a channel Richard Zhao
2012-01-05 9:23 ` Shawn Guo
2012-01-05 9:19 ` Richard Zhao [this message]
2012-01-05 9:34 ` Eric Miao
2012-01-05 9:54 ` Shawn Guo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120105091904.GO2414@b20223-02.ap.freescale.net \
--to=richard.zhao@freescale.com \
--cc=arnd@arndb.de \
--cc=dan.j.williams@intel.com \
--cc=eric.miao@linaro.org \
--cc=kernel@pengutronix.de \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=patches@linaro.org \
--cc=richard.zhao@linaro.org \
--cc=shawn.guo@linaro.org \
--cc=vinod.koul@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®