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Date: Fri, 9 May 2014 14:21:05 +0300
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
Message-ID: <20140509112105.GS3722@lahna.fi.intel.com>
References: <1399559431-2065-1-git-send-email-mika.westerberg@linux.intel.com>
 <20140509103315.GJ12304@sirena.org.uk>
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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.