spi/pxa2xx: Prevent DMA from transferring too many bytes
authorMika Westerberg <mika.westerberg@linux.intel.com>
Thu, 8 May 2014 14:30:31 +0000 (17:30 +0300)
committerMark Brown <broonie@linaro.org>
Mon, 12 May 2014 21:05:37 +0000 (22:05 +0100)
commit111e0a9dc71ed75baa5e739289b9bdb06fda13be
tree665d90e7a448682bd9430a7bd303d5506de9be30
parentc9eaa447e77efe77b7fa4c953bd62de8297fd6c5
spi/pxa2xx: Prevent DMA from transferring too many bytes

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.

Or that is what it tried to do. What actually happens is that it calls
ALIGN() to the buffer size which aligns it to the next 4-byte boundary
(doesn't truncate). Doing this results 1-3 bytes extra to be transferred.
Furthermore we handle remaining bytes using PIO which results one extra
byte to be transferred. In worst case the driver transfers 4 extra bytes.

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.

Reported-by: Chiau Ee Chew <chiau.ee.chew@intel.com>
Reported-by: Hock Leong Kweh <hock.leong.kweh@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
drivers/spi/spi-pxa2xx-dma.c