From 98ccf14909ba02a41c5925b0b2c92aeeef23d3b9 Mon Sep 17 00:00:00 2001 From: Pierre Ossman Date: Sat, 12 May 2007 00:26:16 +0200 Subject: 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 --- drivers/mmc/card/Kconfig | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) (limited to 'drivers/mmc/card/Kconfig') diff --git a/drivers/mmc/card/Kconfig b/drivers/mmc/card/Kconfig index 9320a8c7323..a49cb9737cd 100644 --- a/drivers/mmc/card/Kconfig +++ b/drivers/mmc/card/Kconfig @@ -14,3 +14,21 @@ config MMC_BLOCK 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. + -- cgit v1.2.3