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