linux/drivers/mmc/card/Kconfig
Pierre Ossman 98ccf14909 mmc: bounce requests for simple hosts
Some hosts cannot do scatter/gather in hardware. Since not doing sg
is such a big performance hit, we (optionally) bounce the requests
to a simple linear buffer that we hand over to the driver.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
2007-07-09 21:22:53 +02:00

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#
# MMC/SD card drivers
#
comment "MMC/SD Card Drivers"
config MMC_BLOCK
tristate "MMC block device driver"
depends on BLOCK
default y
help
Say Y here to enable the MMC block device driver support.
This provides a block device driver, which you can use to
mount the filesystem. Almost everyone wishing MMC support
should say Y or M here.
config MMC_BLOCK_BOUNCE
bool "Use bounce buffer for simple hosts"
depends on MMC_BLOCK
default y
help
SD/MMC is a high latency protocol where it is crucial to
send large requests in order to get high performance. Many
controllers, however, are restricted to continuous memory
(i.e. they can't do scatter-gather), something the kernel
rarely can provide.
Say Y here to help these restricted hosts by bouncing
requests back and forth from a large buffer. You will get
a big performance gain at the cost of up to 64 KiB of
physical memory.
If unsure, say Y here.