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authorDan Williams <dan.j.williams@intel.com>2009-09-09 04:42:50 +0400
committerDan Williams <dan.j.williams@intel.com>2009-09-09 04:42:50 +0400
commit0403e3827788d878163f9ef0541b748b0f88ca5d (patch)
tree2dc73744bd92c268a1310f24668167f130877278 /include
parentf9dd2134374c8de6b911e2b8652c6c9622eaa658 (diff)
downloadlinux-0403e3827788d878163f9ef0541b748b0f88ca5d.tar.xz
dmaengine: add fence support
Some engines optimize operation by reading ahead in the descriptor chain such that descriptor2 may start execution before descriptor1 completes. If descriptor2 depends on the result from descriptor1 then a fence is required (on descriptor2) to disable this optimization. The async_tx api could implicitly identify dependencies via the 'depend_tx' parameter, but that would constrain cases where the dependency chain only specifies a completion order rather than a data dependency. So, provide an ASYNC_TX_FENCE to explicitly identify data dependencies. Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'include')
-rw-r--r--include/linux/async_tx.h3
-rw-r--r--include/linux/dmaengine.h3
2 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/async_tx.h b/include/linux/async_tx.h
index 866e61c4e2e0..a1c486a88e88 100644
--- a/include/linux/async_tx.h
+++ b/include/linux/async_tx.h
@@ -58,11 +58,14 @@ struct dma_chan_ref {
* array.
* @ASYNC_TX_ACK: immediately ack the descriptor, precludes setting up a
* dependency chain
+ * @ASYNC_TX_FENCE: specify that the next operation in the dependency
+ * chain uses this operation's result as an input
*/
enum async_tx_flags {
ASYNC_TX_XOR_ZERO_DST = (1 << 0),
ASYNC_TX_XOR_DROP_DST = (1 << 1),
ASYNC_TX_ACK = (1 << 2),
+ ASYNC_TX_FENCE = (1 << 3),
};
/**
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 1012f1abcb54..4d6c1c925fd4 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -87,6 +87,8 @@ enum dma_transaction_type {
* @DMA_PREP_CONTINUE - indicate to a driver that it is reusing buffers as
* sources that were the result of a previous operation, in the case of a PQ
* operation it continues the calculation with new sources
+ * @DMA_PREP_FENCE - tell the driver that subsequent operations depend
+ * on the result of this operation
*/
enum dma_ctrl_flags {
DMA_PREP_INTERRUPT = (1 << 0),
@@ -98,6 +100,7 @@ enum dma_ctrl_flags {
DMA_PREP_PQ_DISABLE_P = (1 << 6),
DMA_PREP_PQ_DISABLE_Q = (1 << 7),
DMA_PREP_CONTINUE = (1 << 8),
+ DMA_PREP_FENCE = (1 << 9),
};
/**