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* [PATCH v5] dmaengine: cookie bypass for out of order completion
@ 2020-05-13 18:47 Dave Jiang
  0 siblings, 0 replies; only message in thread
From: Dave Jiang @ 2020-05-13 18:47 UTC (permalink / raw)
  To: vkoul; +Cc: dmaengine, swathi.kovvuri, peter.ujfalusi

The cookie tracking in dmaengine expects all submissions completed in
order. Some DMA devices like Intel DSA can complete submissions out of
order, especially if configured with a work queue sharing multiple DMA
engines. Add a status DMA_OUT_OF_ORDER that tx_status can be returned for
those DMA devices. The user should use callbacks to track the completion
rather than the DMA cookie. This would address the issue of dmatest
complaining that descriptors are "busy" when the cookie count goes
backwards due to out of order completion. Add DMA_COMPLETION_NO_ORDER
DMA capability to allow the driver to flag the device's ability to complete
operations out of order.

Reported-by: Swathi Kovvuri <swathi.kovvuri@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Tested-by: Swathi Kovvuri <swathi.kovvuri@intel.com>
---

v5:
- Additional clarification in documentation. (peter)
v4:
- Add block for polled in dmatest. Need better enabling in future to solve
  per channel capability for out of order vs poll. (peter)
v3:
- v2 mailed wrong patch
v2:
- Add DMA capability (vinod)
- Add documentation (vinod)

 Documentation/driver-api/dmaengine/provider.rst |   19 +++++++++++++++++++
 drivers/dma/dmatest.c                           |   11 ++++++++++-
 drivers/dma/idxd/dma.c                          |    3 ++-
 include/linux/dmaengine.h                       |    2 ++
 4 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/Documentation/driver-api/dmaengine/provider.rst b/Documentation/driver-api/dmaengine/provider.rst
index 56e5833e8a07..ce68315482b1 100644
--- a/Documentation/driver-api/dmaengine/provider.rst
+++ b/Documentation/driver-api/dmaengine/provider.rst
@@ -239,6 +239,22 @@ Currently, the types available are:
     want to transfer a portion of uncompressed data directly to the
     display to print it
 
+- DMA_COMPLETION_NO_ORDER
+
+  - The device does not support in order completion.
+
+  - The driver should return DMA_OUT_OF_ORDER for device_tx_status if
+    the device is setting this capability.
+
+  - All cookie tracking and checking API should be treated as invalid if
+    the device exports this capability.
+
+  - At this point, this is incompatible with polling option for dmatest.
+
+  - If this cap is set, the user is recommended to provide an unique
+    identifier for each descriptor sent to the DMA device in order to
+    properly track the completion.
+
 These various types will also affect how the source and destination
 addresses change over time.
 
@@ -399,6 +415,9 @@ supported.
   - In the case of a cyclic transfer, it should only take into
     account the current period.
 
+  - Should return DMA_OUT_OF_ORDER if the device does not support in order
+    completion and is completing the operation out of order.
+
   - This function can be called in an interrupt context.
 
 - device_config
diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index a2cadfa2e6d7..93c7c56af5f2 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -821,7 +821,10 @@ static int dmatest_func(void *data)
 			result("test timed out", total_tests, src->off, dst->off,
 			       len, 0);
 			goto error_unmap_continue;
-		} else if (status != DMA_COMPLETE) {
+		} else if (status != DMA_COMPLETE &&
+			   !(dma_has_cap(DMA_COMPLETION_NO_ORDER,
+					 dev->cap_mask) &&
+			     status == DMA_OUT_OF_ORDER)) {
 			result(status == DMA_ERROR ?
 			       "completion error status" :
 			       "completion busy status", total_tests, src->off,
@@ -999,6 +1002,12 @@ static int dmatest_add_channel(struct dmatest_info *info,
 	dtc->chan = chan;
 	INIT_LIST_HEAD(&dtc->threads);
 
+	if (dma_has_cap(DMA_COMPLETION_NO_ORDER, dma_dev->cap_mask) &&
+	    info->params.polled) {
+		info->params.polled = false;
+		pr_warn("DMA_COMPLETION_NO_ORDER, polled disabled\n");
+	}
+
 	if (dma_has_cap(DMA_MEMCPY, dma_dev->cap_mask)) {
 		if (dmatest == 0) {
 			cnt = dmatest_add_threads(info, dtc, DMA_MEMCPY);
diff --git a/drivers/dma/idxd/dma.c b/drivers/dma/idxd/dma.c
index c64c1429d160..0c892cbd72e0 100644
--- a/drivers/dma/idxd/dma.c
+++ b/drivers/dma/idxd/dma.c
@@ -133,7 +133,7 @@ static enum dma_status idxd_dma_tx_status(struct dma_chan *dma_chan,
 					  dma_cookie_t cookie,
 					  struct dma_tx_state *txstate)
 {
-	return dma_cookie_status(dma_chan, cookie, txstate);
+	return DMA_OUT_OF_ORDER;
 }
 
 /*
@@ -174,6 +174,7 @@ int idxd_register_dma_device(struct idxd_device *idxd)
 	INIT_LIST_HEAD(&dma->channels);
 	dma->dev = &idxd->pdev->dev;
 
+	dma_cap_set(DMA_COMPLETION_NO_ORDER, dma->cap_mask);
 	dma->device_release = idxd_dma_release;
 
 	if (idxd->hw.opcap.bits[0] & IDXD_OPCAP_MEMMOVE) {
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 21065c04c4ac..1123f4d15bae 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -39,6 +39,7 @@ enum dma_status {
 	DMA_IN_PROGRESS,
 	DMA_PAUSED,
 	DMA_ERROR,
+	DMA_OUT_OF_ORDER,
 };
 
 /**
@@ -61,6 +62,7 @@ enum dma_transaction_type {
 	DMA_SLAVE,
 	DMA_CYCLIC,
 	DMA_INTERLEAVE,
+	DMA_COMPLETION_NO_ORDER,
 /* last transaction type for creation of the capabilities mask */
 	DMA_TX_TYPE_END,
 };


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2020-05-13 18:47 [PATCH v5] dmaengine: cookie bypass for out of order completion Dave Jiang

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