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dmaengine, async_tx: add a "no channel switch" allocator

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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>
This commit is contained in:
Dan Williams 2009-09-08 17:42:51 -07:00
parent 0403e38277
commit 138f4c359d
4 changed files with 57 additions and 1 deletions
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10
include/linux/dmaengine.h
View file

@ -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);