From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Mark Brown <broonie@kernel.org>
Cc: linux-kernel@vger.kernel.org, Eric Miao <eric.y.miao@gmail.com>,
Russell King <linux@arm.linux.org.uk>,
Haojian Zhuang <haojian.zhuang@gmail.com>,
Chiau Ee Chew <chiau.ee.chew@intel.com>,
Hock Leong Kweh <hock.leong.kweh@intel.com>
Subject: Re: [PATCH] spi/pxa2xx: Prevent DMA from transferring too many bytes
Date: Fri, 9 May 2014 14:21:05 +0300 [thread overview]
Message-ID: <20140509112105.GS3722@lahna.fi.intel.com> (raw)
In-Reply-To: <20140509103315.GJ12304@sirena.org.uk>
On Fri, May 09, 2014 at 11:33:15AM +0100, Mark Brown wrote:
> On Thu, May 08, 2014 at 05:30:31PM +0300, Mika Westerberg wrote:
> > In case we are doing DMA transfer and the size of the buffer is not multiple
> > of 4 bytes the driver truncates that to 4-byte boundary and tries to handle
> > remaining bytes using PIO.
>
> ...
>
> > While investigating this it turned out that the DMA hardware doesn't even
> > have such limitation so we can solve this by dropping the code that tries
> > to handle unaligned bytes.
>
> Is this definitely the case for all of the IPs using this driver? It
> seems like something which might have been present in actual PXA
> implemenetations but got fixed in later revisons used with x86. Equally
> well the current code is clearly broken either way so I'm not sure that
> problems with older systems should be a barrier to merging the patch but
> it seems better to check.
This code came with x86 LPSS implementation originally. The PXA one,
which lives in a different file (spi-pxa2xx-pxadma.c) didn't have any
such checks AFAIK.
next prev parent reply other threads:[~2014-05-09 11:21 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-08 14:30 [PATCH] spi/pxa2xx: Prevent DMA from transferring too many bytes Mika Westerberg
2014-05-09 10:33 ` Mark Brown
2014-05-09 11:21 ` Mika Westerberg [this message]
2014-05-09 11:27 ` Mark Brown
2014-05-12 7:08 ` Mika Westerberg
2014-05-12 21:06 ` Mark Brown
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