mmc: sdhci: avoid unnecessary mapping/unmapping of align buffer
commit
edd63fcc97cdb53279a7c43fa1691f5913d92793 upstream.
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>
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>