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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 /drivers/dma
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 'drivers/dma')
-rw-r--r--drivers/dma/Kconfig4
-rw-r--r--drivers/dma/dmaengine.c40
2 files changed, 44 insertions, 0 deletions
diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 912a51b5cbd..ddcd9793b25 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -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.
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 96598479eec..d5bc628d207 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -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;