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>
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

View File

@ -81,6 +81,10 @@ async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
struct dma_device *device = chan->device;
struct dma_async_tx_descriptor *intr_tx = (void *) ~0;
#ifdef CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH
BUG();
#endif
/* first check to see if we can still append to depend_tx */
spin_lock_bh(&depend_tx->lock);
if (depend_tx->parent && depend_tx->chan == tx->chan) {

View File

@ -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.

View File

@ -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;

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);