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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 /include/linux/dmaengine.h
parent0403e3827788d878163f9ef0541b748b0f88ca5d (diff)
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 'include/linux/dmaengine.h')
-rw-r--r--include/linux/dmaengine.h10
1 files changed, 9 insertions, 1 deletions
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 4d6c1c925fd4..86853ed7970b 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -48,6 +48,9 @@ enum dma_status {
/**
* enum dma_transaction_type - DMA transaction types/indexes
+ *
+ * Note: The DMA_ASYNC_TX capability is not to be set by drivers. It is
+ * automatically set as dma devices are registered.
*/
enum dma_transaction_type {
DMA_MEMCPY,
@@ -61,6 +64,7 @@ enum dma_transaction_type {
DMA_MEMCPY_CRC32C,
DMA_INTERRUPT,
DMA_PRIVATE,
+ DMA_ASYNC_TX,
DMA_SLAVE,
};
@@ -396,7 +400,11 @@ static inline void net_dmaengine_put(void)
#ifdef CONFIG_ASYNC_TX_DMA
#define async_dmaengine_get() dmaengine_get()
#define async_dmaengine_put() dmaengine_put()
+#ifdef CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH
+#define async_dma_find_channel(type) dma_find_channel(DMA_ASYNC_TX)
+#else
#define async_dma_find_channel(type) dma_find_channel(type)
+#endif /* CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH */
#else
static inline void async_dmaengine_get(void)
{
@@ -409,7 +417,7 @@ async_dma_find_channel(enum dma_transaction_type type)
{
return NULL;
}
-#endif
+#endif /* CONFIG_ASYNC_TX_DMA */
dma_cookie_t dma_async_memcpy_buf_to_buf(struct dma_chan *chan,
void *dest, void *src, size_t len);