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authorDan Williams <dan.j.williams@intel.com>2009-09-08 17:42:51 -0700
committerDan Williams <dan.j.williams@intel.com>2009-09-08 17:42:51 -0700
commit138f4c359d23d2ec38d18bd70dd9613ae515fe93 (patch)
treead7fafba6eac74d9d92ade839a65171466d67a70 /drivers/dma/Kconfig
parent0403e3827788d878163f9ef0541b748b0f88ca5d (diff)
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dmaengine, async_tx: add a "no channel switch" allocator
Channel switching is problematic for some dmaengine drivers as the architecture precludes separating the ->prep from ->submit. In these cases the driver can select ASYNC_TX_DISABLE_CHANNEL_SWITCH to modify the async_tx allocator to only return channels that support all of the required asynchronous operations. For example MD_RAID456=y selects support for asynchronous xor, xor validate, pq, pq validate, and memcpy. When ASYNC_TX_DISABLE_CHANNEL_SWITCH=y any channel with all these capabilities is marked DMA_ASYNC_TX allowing async_tx_find_channel() to quickly locate compatible channels with the guarantee that dependency chains will remain on one channel. When ASYNC_TX_DISABLE_CHANNEL_SWITCH=n async_tx_find_channel() may select channels that lead to operation chains that need to cross channel boundaries using the async_tx channel switch capability. Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/dma/Kconfig')
-rw-r--r--drivers/dma/Kconfig4
1 files changed, 4 insertions, 0 deletions
diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 912a51b5cbd3..ddcd9793b25c 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -17,11 +17,15 @@ if DMADEVICES
comment "DMA Devices"
+config ASYNC_TX_DISABLE_CHANNEL_SWITCH
+ bool
+
config INTEL_IOATDMA
tristate "Intel I/OAT DMA support"
depends on PCI && X86
select DMA_ENGINE
select DCA
+ select ASYNC_TX_DISABLE_CHANNEL_SWITCH
help
Enable support for the Intel(R) I/OAT DMA engine present
in recent Intel Xeon chipsets.