From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jisheng Zhang Subject: Re: [PATCH] i2c: designware: use {readl|writel}_relaxed instead of readl/writel Date: Fri, 19 Dec 2014 10:43:15 +0800 Message-ID: <20141219104315.0ccbba9c@xhacker> References: <1418279201-3886-1-git-send-email-jszhang@marvell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1418279201-3886-1-git-send-email-jszhang-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org" , "linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" Cc: "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: linux-i2c@vger.kernel.org Dear all, Is there any issue I need to resolve so that the patch can be merged? Thanks in advance, Jisheng On Wed, 10 Dec 2014 22:26:41 -0800 Jisheng Zhang wrote: > readl/writel is too expensive especially on Cortex A9 w/ outer L2 cache. > This introduces i2c read/write errors on Marvell BG2/BG2Q SoCs when there > are heavy L2 cache maintenance operations at the same time. > > The driver does not perform DMA, so it's safe to use the relaxed version. > From another side, the relaxed io accessor macros are available on all > architectures now, so we can use the relaxed versions instead. > > Signed-off-by: Jisheng Zhang > --- > drivers/i2c/busses/i2c-designware-core.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-designware-core.c > b/drivers/i2c/busses/i2c-designware-core.c index 23628b7..e279948 100644 > --- a/drivers/i2c/busses/i2c-designware-core.c > +++ b/drivers/i2c/busses/i2c-designware-core.c > @@ -170,10 +170,10 @@ u32 dw_readl(struct dw_i2c_dev *dev, int offset) > u32 value; > > if (dev->accessor_flags & ACCESS_16BIT) > - value = readw(dev->base + offset) | > - (readw(dev->base + offset + 2) << 16); > + value = readw_relaxed(dev->base + offset) | > + (readw_relaxed(dev->base + offset + 2) << 16); > else > - value = readl(dev->base + offset); > + value = readl_relaxed(dev->base + offset); > > if (dev->accessor_flags & ACCESS_SWAP) > return swab32(value); > @@ -187,10 +187,10 @@ void dw_writel(struct dw_i2c_dev *dev, u32 b, int > offset) b = swab32(b); > > if (dev->accessor_flags & ACCESS_16BIT) { > - writew((u16)b, dev->base + offset); > - writew((u16)(b >> 16), dev->base + offset + 2); > + writew_relaxed((u16)b, dev->base + offset); > + writew_relaxed((u16)(b >> 16), dev->base + offset + 2); > } else { > - writel(b, dev->base + offset); > + writel_relaxed(b, dev->base + offset); > } > } >