mmc: sdhci: avoid unnecessary mapping/unmapping of align buffer

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Unnecessarily mapping and unmapping the align buffer for SD cards is
expensive: performance measurements on iMX6 show that this gives a hit
of 10% on hdparm buffered disk reads.

MMC/SD card IO comes from the mm/vfs which gives us page based IO, so
for this case, the align buffer is not going to be used.  However, we
still map and unmap this buffer.

Eliminate this by switching the align buffer to be a DMA coherent
buffer, which needs no DMA maintenance to access the buffer.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: stable@vger.kernel.org # v4.5+
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

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Russell King 2016-01-26 13:39:50 +00:00 • committed by Ulf Hansson

parent 71fcbda0fc

commit edd63fcc97

1 changed files with 18 additions and 36 deletions

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drivers/mmc/host/sdhci.c

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