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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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40
drivers/dma/dmaengine.c
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@@ -608,6 +608,40 @@ void dmaengine_put(void)
}
EXPORT_SYMBOL(dmaengine_put);
static bool device_has_all_tx_types(struct dma_device *device)
{
/* A device that satisfies this test has channels that will never cause
* an async_tx channel switch event as all possible operation types can
* be handled.
*/
#ifdef CONFIG_ASYNC_TX_DMA
if (!dma_has_cap(DMA_INTERRUPT, device->cap_mask))
return false;
#endif
#if defined(CONFIG_ASYNC_MEMCPY) || defined(CONFIG_ASYNC_MEMCPY_MODULE)
if (!dma_has_cap(DMA_MEMCPY, device->cap_mask))
return false;
#endif
#if defined(CONFIG_ASYNC_MEMSET) || defined(CONFIG_ASYNC_MEMSET_MODULE)
if (!dma_has_cap(DMA_MEMSET, device->cap_mask))
return false;
#endif
#if defined(CONFIG_ASYNC_XOR) || defined(CONFIG_ASYNC_XOR_MODULE)
if (!dma_has_cap(DMA_XOR, device->cap_mask))
return false;
#endif
#if defined(CONFIG_ASYNC_PQ) || defined(CONFIG_ASYNC_PQ_MODULE)
if (!dma_has_cap(DMA_PQ, device->cap_mask))
return false;
#endif
return true;
}
static int get_dma_id(struct dma_device *device)
{
int rc;
@@ -665,6 +699,12 @@ int dma_async_device_register(struct dma_device *device)
BUG_ON(!device->device_issue_pending);
BUG_ON(!device->dev);
/* note: this only matters in the
* CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH=y case
*/
if (device_has_all_tx_types(device))
dma_cap_set(DMA_ASYNC_TX, device->cap_mask);
idr_ref = kmalloc(sizeof(*idr_ref), GFP_KERNEL);
if (!idr_ref)
return -ENOMEM;