[PATCH v2 0/8] dmaengine: Add new API to combine onfiguration and descriptor preparation

[PATCH v2 0/8] dmaengine: Add new API to combine onfiguration and descriptor preparation

[Frank Li]

Previously, configuration and preparation required two separate calls. This
works well when configuration is done only once during initialization.

However, in cases where the burst length or source/destination address must
be adjusted for each transfer, calling two functions is verbose.

	if (dmaengine_slave_config(chan, &sconf)) {
		dev_err(dev, "DMA slave config fail\n");
		return -EIO;
	}

	tx = dmaengine_prep_slave_single(chan, dma_local, len, dir, flags);

After new API added

	tx = dmaengine_prep_config_single(chan, dma_local, len, dir, flags, &sconf);

Additional, prevous two calls requires additional locking to ensure both
steps complete atomically.

    mutex_lock()
    dmaengine_slave_config()
    dmaengine_prep_slave_single()
    mutex_unlock()

after new API added, mutex lock can be moved. See patch
     nvmet: pci-epf: Use dmaengine_prep_config_single_safe() API

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Changes in v2:
- Use name dmaengine_prep_config_single() and dmaengine_prep_config_sg()
- Add _safe version to avoid confuse, which needn't additional mutex.
- Update document/
- Update commit message. add () for function name. Use upcase for subject.
- Add more explain for remove lock.
- Link to v1: https://lore.kernel.org/r/20251208-dma_prep_config-v1-0-53490c5e1e2a@nxp.com

---
Frank Li (8):
      dmaengine: Add API to combine configuration and preparation (sg and single)
      PCI: endpoint: pci-epf-test: Use dmaenigne_prep_config_single() to simplify code
      dmaengine: dw-edma: Use new .device_prep_config_sg() callback
      dmaengine: dw-edma: Pass dma_slave_config to dw_edma_device_transfer()
      nvmet: pci-epf: Remove unnecessary dmaengine_terminate_sync() on each DMA transfer
      nvmet: pci-epf: Use dmaengine_prep_config_single_safe() API
      PCI: epf-mhi: Use dmaengine_prep_config_single() to simplify code
      crypto: atmel: Use dmaengine_prep_config_single() API

 Documentation/driver-api/dmaengine/client.rst |   9 +++
 drivers/crypto/atmel-aes.c                    |  10 +--
 drivers/dma/dw-edma/dw-edma-core.c            |  36 ++++++---
 drivers/nvme/target/pci-epf.c                 |  21 ++----
 drivers/pci/endpoint/functions/pci-epf-mhi.c  |  52 ++++---------
 drivers/pci/endpoint/functions/pci-epf-test.c |   8 +-
 include/linux/dmaengine.h                     | 103 ++++++++++++++++++++++++--
 7 files changed, 156 insertions(+), 83 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20251204-dma_prep_config-654170d245a2

Best regards,
--
Frank Li <Frank.Li@nxp.com>

[PATCH v2 1/8] dmaengine: Add API to combine configuration and preparation (sg and single)

[Frank Li]

Previously, configuration and preparation required two separate calls. This
works well when configuration is done only once during initialization.

However, in cases where the burst length or source/destination address must
be adjusted for each transfer, calling two functions is verbose and
requires additional locking to ensure both steps complete atomically.

Add a new API dmaengine_prep_config_single() and dmaengine_prep_config_sg()
and callback device_prep_config_sg() that combines configuration and
preparation into a single operation. If the configuration argument is
passed as NULL, fall back to the existing implementation.

Add a new API dmaengine_prep_config_single_safe() and
dmaengine_prep_config_sg_safe() for re-entrancy, which require driver
implement callback device_prep_config_sg().

Tested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change in v2
- add () for function
- use short name device_prep_sg(), remove "slave" and "config". the 'slave'
is reduntant. after remove slave, the function name is difference existed
one, so remove _config suffix.
---
 Documentation/driver-api/dmaengine/client.rst |   9 +++
 include/linux/dmaengine.h                     | 103 ++++++++++++++++++++++++--
 2 files changed, 105 insertions(+), 7 deletions(-)

diff --git a/Documentation/driver-api/dmaengine/client.rst b/Documentation/driver-api/dmaengine/client.rst
index d491e385d61a98b8a804cd823caf254a2dc62cf4..02c45b7d7a779421411eb9c68325cdedafcfe3b1 100644
--- a/Documentation/driver-api/dmaengine/client.rst
+++ b/Documentation/driver-api/dmaengine/client.rst
@@ -80,6 +80,10 @@ The details of these operations are:
 
   - slave_sg: DMA a list of scatter gather buffers from/to a peripheral
 
+  - config_sg: Similar with slave_sg, just pass down dma_slave_config
+    struct to avoid call dmaengine_slave_config() every time if need
+    adjust burst length or FIFO address.
+
   - peripheral_dma_vec: DMA an array of scatter gather buffers from/to a
     peripheral. Similar to slave_sg, but uses an array of dma_vec
     structures instead of a scatterlist.
@@ -106,6 +110,11 @@ The details of these operations are:
 		unsigned int sg_len, enum dma_data_direction direction,
 		unsigned long flags);
 
+     struct dma_async_tx_descriptor *dmaengine_prep_config_sg(
+		struct dma_chan *chan, struct scatterlist *sgl,
+		unsigned int sg_len, enum dma_transfer_direction dir,
+		unsigned long flags, struct dma_slave_config *config);
+
      struct dma_async_tx_descriptor *dmaengine_prep_peripheral_dma_vec(
 		struct dma_chan *chan, const struct dma_vec *vecs,
 		size_t nents, enum dma_data_direction direction,
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 99efe2b9b4ea9844ca6161208362ef18ef111d96..276dca760f95e1131f5ff5bf69752c4c9cb1bcad 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -835,6 +835,8 @@ struct dma_filter {
  *	where the address and size of each segment is located in one entry of
  *	the dma_vec array.
  * @device_prep_slave_sg: prepares a slave dma operation
+ *	(Deprecated, use @device_prep_config_sg)
+ * @device_prep_config_sg: prepares a slave DMA operation with dma_slave_config
  * @device_prep_dma_cyclic: prepare a cyclic dma operation suitable for audio.
  *	The function takes a buffer of size buf_len. The callback function will
  *	be called after period_len bytes have been transferred.
@@ -934,6 +936,11 @@ struct dma_device {
 		struct dma_chan *chan, struct scatterlist *sgl,
 		unsigned int sg_len, enum dma_transfer_direction direction,
 		unsigned long flags, void *context);
+	struct dma_async_tx_descriptor *(*device_prep_config_sg)(
+		struct dma_chan *chan, struct scatterlist *sgl,
+		unsigned int sg_len, enum dma_transfer_direction direction,
+		unsigned long flags, struct dma_slave_config *config,
+		void *context);
 	struct dma_async_tx_descriptor *(*device_prep_dma_cyclic)(
 		struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
 		size_t period_len, enum dma_transfer_direction direction,
@@ -974,22 +981,85 @@ static inline bool is_slave_direction(enum dma_transfer_direction direction)
 	       (direction == DMA_DEV_TO_DEV);
 }
 
-static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_single(
-	struct dma_chan *chan, dma_addr_t buf, size_t len,
-	enum dma_transfer_direction dir, unsigned long flags)
+/*
+ * Re-entrancy and locking considerations for callers:
+ *
+ * dmaengine_prep_config_single(sg)_safe() is re-entrant and requires the
+ * DMA engine driver to implement device_prep_config_sg(). It returns NULL
+ * if device_prep_config_sg() is not implemented.
+ *
+ * The unsafe variant (without the _safe suffix) falls back to calling
+ * dmaengine_slave_config() and dmaengine_prep_slave_sg() separately.
+ * In this case, additional locking may be required, depending on the
+ * DMA consumer's usage.
+ */
+static inline struct dma_async_tx_descriptor *
+dmaengine_prep_config_sg_safe(struct dma_chan *chan, struct scatterlist *sgl,
+	unsigned int sg_len, enum dma_transfer_direction dir,
+	unsigned long flags, struct dma_slave_config *config)
+{
+	if (!chan || !chan->device || !chan->device->device_prep_config_sg)
+		return NULL;
+
+	return chan->device->device_prep_config_sg(chan, sgl, sg_len,
+						   dir, flags, config, NULL);
+}
+
+static inline struct dma_async_tx_descriptor *
+dmaengine_prep_config_single_safe(struct dma_chan *chan, dma_addr_t buf,
+	size_t len, enum dma_transfer_direction dir, unsigned long flags,
+	struct dma_slave_config *config)
 {
 	struct scatterlist sg;
+
 	sg_init_table(&sg, 1);
 	sg_dma_address(&sg) = buf;
 	sg_dma_len(&sg) = len;
 
-	if (!chan || !chan->device || !chan->device->device_prep_slave_sg)
+	if (!chan || !chan->device || !chan->device->device_prep_config_sg)
+		return NULL;
+
+	return chan->device->device_prep_config_sg(chan, &sg, 1, dir,
+						   flags, config, NULL);
+}
+
+static inline struct dma_async_tx_descriptor *
+dmaengine_prep_config_single(struct dma_chan *chan, dma_addr_t buf, size_t len,
+	enum dma_transfer_direction dir, unsigned long flags,
+	struct dma_slave_config *config)
+{
+	struct scatterlist sg;
+
+	sg_init_table(&sg, 1);
+	sg_dma_address(&sg) = buf;
+	sg_dma_len(&sg) = len;
+
+	if (!chan || !chan->device)
+		return NULL;
+
+	if (chan->device->device_prep_config_sg)
+		return dmaengine_prep_config_sg_safe(chan, &sg, 1, dir,
+						     flags, config);
+
+	if (config)
+		if (dmaengine_slave_config(chan, config))
+			return NULL;
+
+	if (!chan->device->device_prep_slave_sg)
 		return NULL;
 
 	return chan->device->device_prep_slave_sg(chan, &sg, 1,
 						  dir, flags, NULL);
 }
 
+static inline struct dma_async_tx_descriptor *
+dmaengine_prep_slave_single(struct dma_chan *chan, dma_addr_t buf, size_t len,
+			    enum dma_transfer_direction dir,
+			    unsigned long flags)
+{
+	return dmaengine_prep_config_single(chan, buf, len, dir, flags, NULL);
+}
+
 /**
  * dmaengine_prep_peripheral_dma_vec() - Prepare a DMA scatter-gather descriptor
  * @chan: The channel to be used for this descriptor
@@ -1009,17 +1079,36 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_peripheral_dma_vec(
 							    dir, flags);
 }
 
-static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_sg(
+static inline struct dma_async_tx_descriptor *dmaengine_prep_config_sg(
 	struct dma_chan *chan, struct scatterlist *sgl,	unsigned int sg_len,
-	enum dma_transfer_direction dir, unsigned long flags)
+	enum dma_transfer_direction dir, unsigned long flags,
+	struct dma_slave_config *config)
 {
-	if (!chan || !chan->device || !chan->device->device_prep_slave_sg)
+	if (!chan || !chan->device)
+		return NULL;
+
+	if (chan->device->device_prep_config_sg)
+		return dmaengine_prep_config_sg_safe(chan, sgl, sg_len,
+					dir, flags, config);
+
+	if (config)
+		if (dmaengine_slave_config(chan, config))
+			return NULL;
+
+	if (!chan->device->device_prep_slave_sg)
 		return NULL;
 
 	return chan->device->device_prep_slave_sg(chan, sgl, sg_len,
 						  dir, flags, NULL);
 }
 
+static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_sg(
+	struct dma_chan *chan, struct scatterlist *sgl, unsigned int sg_len,
+	enum dma_transfer_direction dir, unsigned long flags)
+{
+	return dmaengine_prep_config_sg(chan, sgl, sg_len, dir, flags, NULL);
+}
+
 #ifdef CONFIG_RAPIDIO_DMA_ENGINE
 struct rio_dma_ext;
 static inline struct dma_async_tx_descriptor *dmaengine_prep_rio_sg(

-- 
2.34.1

[PATCH v2 2/8] PCI: endpoint: pci-epf-test: Use dmaenigne_prep_config_single() to simplify code

[Frank Li]

Use dmaenigne_prep_config_single() to simplify code.

No functional change.

Tested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
 drivers/pci/endpoint/functions/pci-epf-test.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index debd235253c5ba54eb8f06d13261c407ee3768ec..95b046c678da7ca4a0d9616acdd544251dc05aac 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -162,12 +162,8 @@ static int pci_epf_test_data_transfer(struct pci_epf_test *epf_test,
 		else
 			sconf.src_addr = dma_remote;
 
-		if (dmaengine_slave_config(chan, &sconf)) {
-			dev_err(dev, "DMA slave config fail\n");
-			return -EIO;
-		}
-		tx = dmaengine_prep_slave_single(chan, dma_local, len, dir,
-						 flags);
+		tx = dmaengine_prep_config_single(chan, dma_local, len,
+						  dir, flags, &sconf);
 	} else {
 		tx = dmaengine_prep_dma_memcpy(chan, dma_dst, dma_src, len,
 					       flags);

-- 
2.34.1

[PATCH v2 3/8] dmaengine: dw-edma: Use new .device_prep_config_sg() callback

[Frank Li]

Use the new .device_prep_config_sg() callback to combine configuration and
descriptor preparation.

No functional changes.

Tested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
 drivers/dma/dw-edma/dw-edma-core.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index 8e5f7defa6b678eefe0f312ebc59f654677c744f..e005b7bdaee156a3f4573b4734f50e3e47553dd2 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -532,10 +532,11 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)
 }
 
 static struct dma_async_tx_descriptor *
-dw_edma_device_prep_slave_sg(struct dma_chan *dchan, struct scatterlist *sgl,
-			     unsigned int len,
-			     enum dma_transfer_direction direction,
-			     unsigned long flags, void *context)
+dw_edma_device_prep_config_sg(struct dma_chan *dchan, struct scatterlist *sgl,
+			      unsigned int len,
+			      enum dma_transfer_direction direction,
+			      unsigned long flags,
+			      struct dma_slave_config *config, void *context)
 {
 	struct dw_edma_transfer xfer;
 
@@ -546,6 +547,9 @@ dw_edma_device_prep_slave_sg(struct dma_chan *dchan, struct scatterlist *sgl,
 	xfer.flags = flags;
 	xfer.type = EDMA_XFER_SCATTER_GATHER;
 
+	if (config)
+		dw_edma_device_config(dchan, config);
+
 	return dw_edma_device_transfer(&xfer);
 }
 
@@ -815,7 +819,7 @@ static int dw_edma_channel_setup(struct dw_edma *dw, u32 wr_alloc, u32 rd_alloc)
 	dma->device_terminate_all = dw_edma_device_terminate_all;
 	dma->device_issue_pending = dw_edma_device_issue_pending;
 	dma->device_tx_status = dw_edma_device_tx_status;
-	dma->device_prep_slave_sg = dw_edma_device_prep_slave_sg;
+	dma->device_prep_config_sg = dw_edma_device_prep_config_sg;
 	dma->device_prep_dma_cyclic = dw_edma_device_prep_dma_cyclic;
 	dma->device_prep_interleaved_dma = dw_edma_device_prep_interleaved_dma;
 

-- 
2.34.1

[PATCH v2 4/8] dmaengine: dw-edma: Pass dma_slave_config to dw_edma_device_transfer()

[Frank Li]

Pass dma_slave_config to dw_edma_device_transfer() to support atomic
configuration and descriptor preparation when a non-NULL config is
provided to device_prep_config_sg().

Tested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
 drivers/dma/dw-edma/dw-edma-core.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index e005b7bdaee156a3f4573b4734f50e3e47553dd2..1863254bf61eb892cb0cf8934e53b40d32027dfa 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -230,6 +230,15 @@ static int dw_edma_device_config(struct dma_chan *dchan,
 	return 0;
 }
 
+static struct dma_slave_config *
+dw_edma_device_get_config(struct dma_chan *dchan,
+			  struct dma_slave_config *config)
+{
+	struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
+
+	return config ? config : &chan->config;
+}
+
 static int dw_edma_device_pause(struct dma_chan *dchan)
 {
 	struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
@@ -348,7 +357,8 @@ dw_edma_device_tx_status(struct dma_chan *dchan, dma_cookie_t cookie,
 }
 
 static struct dma_async_tx_descriptor *
-dw_edma_device_transfer(struct dw_edma_transfer *xfer)
+dw_edma_device_transfer(struct dw_edma_transfer *xfer,
+			struct dma_slave_config *config)
 {
 	struct dw_edma_chan *chan = dchan2dw_edma_chan(xfer->dchan);
 	enum dma_transfer_direction dir = xfer->direction;
@@ -427,8 +437,8 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer)
 		src_addr = xfer->xfer.il->src_start;
 		dst_addr = xfer->xfer.il->dst_start;
 	} else {
-		src_addr = chan->config.src_addr;
-		dst_addr = chan->config.dst_addr;
+		src_addr = config->src_addr;
+		dst_addr = config->dst_addr;
 	}
 
 	if (dir == DMA_DEV_TO_MEM)
@@ -550,7 +560,7 @@ dw_edma_device_prep_config_sg(struct dma_chan *dchan, struct scatterlist *sgl,
 	if (config)
 		dw_edma_device_config(dchan, config);
 
-	return dw_edma_device_transfer(&xfer);
+	return dw_edma_device_transfer(&xfer, dw_edma_device_get_config(dchan, config));
 }
 
 static struct dma_async_tx_descriptor *
@@ -569,7 +579,7 @@ dw_edma_device_prep_dma_cyclic(struct dma_chan *dchan, dma_addr_t paddr,
 	xfer.flags = flags;
 	xfer.type = EDMA_XFER_CYCLIC;
 
-	return dw_edma_device_transfer(&xfer);
+	return dw_edma_device_transfer(&xfer, dw_edma_device_get_config(dchan, NULL));
 }
 
 static struct dma_async_tx_descriptor *
@@ -585,7 +595,7 @@ dw_edma_device_prep_interleaved_dma(struct dma_chan *dchan,
 	xfer.flags = flags;
 	xfer.type = EDMA_XFER_INTERLEAVED;
 
-	return dw_edma_device_transfer(&xfer);
+	return dw_edma_device_transfer(&xfer, dw_edma_device_get_config(dchan, NULL));
 }
 
 static void dw_hdma_set_callback_result(struct virt_dma_desc *vd,

-- 
2.34.1

[PATCH v2 5/8] nvmet: pci-epf: Remove unnecessary dmaengine_terminate_sync() on each DMA transfer

[Frank Li]

dmaengine_terminate_sync() cancels all pending requests. Calling it for
every DMA transfer is unnecessary and counterproductive. This function is
generally intended for cleanup paths such as module removal, device close,
or unbind operations.

Remove the redundant calls for success path and keep it only at error path.

Tested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
This one also fix stress test failure after remove mutex and use new API
dmaengine_prep_slave_sg_config().
---
 drivers/nvme/target/pci-epf.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/nvme/target/pci-epf.c b/drivers/nvme/target/pci-epf.c
index f858a6c9d7cb90670037a957cebdcbf17dddc43b..56b1c6a7706a9e2dd9d8aaf17b440129b948486c 100644
--- a/drivers/nvme/target/pci-epf.c
+++ b/drivers/nvme/target/pci-epf.c
@@ -420,10 +420,9 @@ static int nvmet_pci_epf_dma_transfer(struct nvmet_pci_epf *nvme_epf,
 	if (dma_sync_wait(chan, cookie) != DMA_COMPLETE) {
 		dev_err(dev, "DMA transfer failed\n");
 		ret = -EIO;
+		dmaengine_terminate_sync(chan);
 	}
 
-	dmaengine_terminate_sync(chan);
-
 unmap:
 	dma_unmap_single(dma_dev, dma_addr, seg->length, dir);
 

-- 
2.34.1

[PATCH v2 6/8] nvmet: pci-epf: Use dmaengine_prep_config_single_safe() API

[Frank Li]

Use the new dmaengine_prep_config_single_safe() API to combine the
configuration and descriptor preparation into a single call.

Since dmaengine_prep_config_single_safe() performs the configuration and
preparation atomically and dw edma driver implement prep_config_sg() call
back, so dmaengine_prep_config_single() is reentriable, the mutex can be
removed.

Tested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
 drivers/nvme/target/pci-epf.c | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/drivers/nvme/target/pci-epf.c b/drivers/nvme/target/pci-epf.c
index 56b1c6a7706a9e2dd9d8aaf17b440129b948486c..8b5ea5d4c79dfd461b767cfd4033a9e4604c94b1 100644
--- a/drivers/nvme/target/pci-epf.c
+++ b/drivers/nvme/target/pci-epf.c
@@ -388,22 +388,15 @@ static int nvmet_pci_epf_dma_transfer(struct nvmet_pci_epf *nvme_epf,
 		return -EINVAL;
 	}
 
-	mutex_lock(lock);
-
 	dma_dev = dmaengine_get_dma_device(chan);
 	dma_addr = dma_map_single(dma_dev, seg->buf, seg->length, dir);
 	ret = dma_mapping_error(dma_dev, dma_addr);
 	if (ret)
-		goto unlock;
-
-	ret = dmaengine_slave_config(chan, &sconf);
-	if (ret) {
-		dev_err(dev, "Failed to configure DMA channel\n");
-		goto unmap;
-	}
+		return ret;
 
-	desc = dmaengine_prep_slave_single(chan, dma_addr, seg->length,
-					   sconf.direction, DMA_CTRL_ACK);
+	desc = dmaengine_prep_config_single_safe(chan, dma_addr, seg->length,
+						 sconf.direction,
+						 DMA_CTRL_ACK, &sconf);
 	if (!desc) {
 		dev_err(dev, "Failed to prepare DMA\n");
 		ret = -EIO;
@@ -426,9 +419,6 @@ static int nvmet_pci_epf_dma_transfer(struct nvmet_pci_epf *nvme_epf,
 unmap:
 	dma_unmap_single(dma_dev, dma_addr, seg->length, dir);
 
-unlock:
-	mutex_unlock(lock);
-
 	return ret;
 }
 

-- 
2.34.1

[PATCH v2 7/8] PCI: epf-mhi: Use dmaengine_prep_config_single() to simplify code

[Frank Li]

Use dmaengine_prep_config_single() to simplify
pci_epf_mhi_edma_read[_sync]() and pci_epf_mhi_edma_write[_sync]().

No functional change.

Tested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Keep mutex lock because sync with other function.
---
 drivers/pci/endpoint/functions/pci-epf-mhi.c | 52 +++++++++-------------------
 1 file changed, 16 insertions(+), 36 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-mhi.c b/drivers/pci/endpoint/functions/pci-epf-mhi.c
index 6643a88c7a0ce38161bc6253c09d29f1c36ba394..0bf51fd467395182161555f83aa78f3839e36773 100644
--- a/drivers/pci/endpoint/functions/pci-epf-mhi.c
+++ b/drivers/pci/endpoint/functions/pci-epf-mhi.c
@@ -328,12 +328,6 @@ static int pci_epf_mhi_edma_read(struct mhi_ep_cntrl *mhi_cntrl,
 	config.direction = DMA_DEV_TO_MEM;
 	config.src_addr = buf_info->host_addr;
 
-	ret = dmaengine_slave_config(chan, &config);
-	if (ret) {
-		dev_err(dev, "Failed to configure DMA channel\n");
-		goto err_unlock;
-	}
-
 	dst_addr = dma_map_single(dma_dev, buf_info->dev_addr, buf_info->size,
 				  DMA_FROM_DEVICE);
 	ret = dma_mapping_error(dma_dev, dst_addr);
@@ -342,9 +336,10 @@ static int pci_epf_mhi_edma_read(struct mhi_ep_cntrl *mhi_cntrl,
 		goto err_unlock;
 	}
 
-	desc = dmaengine_prep_slave_single(chan, dst_addr, buf_info->size,
-					   DMA_DEV_TO_MEM,
-					   DMA_CTRL_ACK | DMA_PREP_INTERRUPT);
+	desc = dmaengine_prep_config_single(chan, dst_addr, buf_info->size,
+					    DMA_DEV_TO_MEM,
+					    DMA_CTRL_ACK | DMA_PREP_INTERRUPT,
+					    &config);
 	if (!desc) {
 		dev_err(dev, "Failed to prepare DMA\n");
 		ret = -EIO;
@@ -399,12 +394,6 @@ static int pci_epf_mhi_edma_write(struct mhi_ep_cntrl *mhi_cntrl,
 	config.direction = DMA_MEM_TO_DEV;
 	config.dst_addr = buf_info->host_addr;
 
-	ret = dmaengine_slave_config(chan, &config);
-	if (ret) {
-		dev_err(dev, "Failed to configure DMA channel\n");
-		goto err_unlock;
-	}
-
 	src_addr = dma_map_single(dma_dev, buf_info->dev_addr, buf_info->size,
 				  DMA_TO_DEVICE);
 	ret = dma_mapping_error(dma_dev, src_addr);
@@ -413,9 +402,10 @@ static int pci_epf_mhi_edma_write(struct mhi_ep_cntrl *mhi_cntrl,
 		goto err_unlock;
 	}
 
-	desc = dmaengine_prep_slave_single(chan, src_addr, buf_info->size,
-					   DMA_MEM_TO_DEV,
-					   DMA_CTRL_ACK | DMA_PREP_INTERRUPT);
+	desc = dmaengine_prep_config_single(chan, src_addr, buf_info->size,
+					    DMA_MEM_TO_DEV,
+					    DMA_CTRL_ACK | DMA_PREP_INTERRUPT,
+					    &config);
 	if (!desc) {
 		dev_err(dev, "Failed to prepare DMA\n");
 		ret = -EIO;
@@ -502,12 +492,6 @@ static int pci_epf_mhi_edma_read_async(struct mhi_ep_cntrl *mhi_cntrl,
 	config.direction = DMA_DEV_TO_MEM;
 	config.src_addr = buf_info->host_addr;
 
-	ret = dmaengine_slave_config(chan, &config);
-	if (ret) {
-		dev_err(dev, "Failed to configure DMA channel\n");
-		goto err_unlock;
-	}
-
 	dst_addr = dma_map_single(dma_dev, buf_info->dev_addr, buf_info->size,
 				  DMA_FROM_DEVICE);
 	ret = dma_mapping_error(dma_dev, dst_addr);
@@ -516,9 +500,10 @@ static int pci_epf_mhi_edma_read_async(struct mhi_ep_cntrl *mhi_cntrl,
 		goto err_unlock;
 	}
 
-	desc = dmaengine_prep_slave_single(chan, dst_addr, buf_info->size,
-					   DMA_DEV_TO_MEM,
-					   DMA_CTRL_ACK | DMA_PREP_INTERRUPT);
+	desc = dmaengine_prep_config_single(chan, dst_addr, buf_info->size,
+					    DMA_DEV_TO_MEM,
+					    DMA_CTRL_ACK | DMA_PREP_INTERRUPT,
+					    &config);
 	if (!desc) {
 		dev_err(dev, "Failed to prepare DMA\n");
 		ret = -EIO;
@@ -581,12 +566,6 @@ static int pci_epf_mhi_edma_write_async(struct mhi_ep_cntrl *mhi_cntrl,
 	config.direction = DMA_MEM_TO_DEV;
 	config.dst_addr = buf_info->host_addr;
 
-	ret = dmaengine_slave_config(chan, &config);
-	if (ret) {
-		dev_err(dev, "Failed to configure DMA channel\n");
-		goto err_unlock;
-	}
-
 	src_addr = dma_map_single(dma_dev, buf_info->dev_addr, buf_info->size,
 				  DMA_TO_DEVICE);
 	ret = dma_mapping_error(dma_dev, src_addr);
@@ -595,9 +574,10 @@ static int pci_epf_mhi_edma_write_async(struct mhi_ep_cntrl *mhi_cntrl,
 		goto err_unlock;
 	}
 
-	desc = dmaengine_prep_slave_single(chan, src_addr, buf_info->size,
-					   DMA_MEM_TO_DEV,
-					   DMA_CTRL_ACK | DMA_PREP_INTERRUPT);
+	desc = dmaengine_prep_config_single(chan, src_addr, buf_info->size,
+					    DMA_MEM_TO_DEV,
+					    DMA_CTRL_ACK | DMA_PREP_INTERRUPT,
+					    &config);
 	if (!desc) {
 		dev_err(dev, "Failed to prepare DMA\n");
 		ret = -EIO;

-- 
2.34.1

[PATCH v2 8/8] crypto: atmel: Use dmaengine_prep_config_single() API

[Frank Li]

Using new API dmaengine_prep_config_single() to simple code.

No functional change.

Tested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
 drivers/crypto/atmel-aes.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/crypto/atmel-aes.c b/drivers/crypto/atmel-aes.c
index 3a2684208dda9ee45d71b4bc2958be293a4fb6fe..e300672ffd7185b0f5bf356c2376681537047def 100644
--- a/drivers/crypto/atmel-aes.c
+++ b/drivers/crypto/atmel-aes.c
@@ -795,7 +795,6 @@ static int atmel_aes_dma_transfer_start(struct atmel_aes_dev *dd,
 	struct dma_slave_config config;
 	dma_async_tx_callback callback;
 	struct atmel_aes_dma *dma;
-	int err;
 
 	memset(&config, 0, sizeof(config));
 	config.src_addr_width = addr_width;
@@ -820,12 +819,9 @@ static int atmel_aes_dma_transfer_start(struct atmel_aes_dev *dd,
 		return -EINVAL;
 	}
 
-	err = dmaengine_slave_config(dma->chan, &config);
-	if (err)
-		return err;
-
-	desc = dmaengine_prep_slave_sg(dma->chan, dma->sg, dma->sg_len, dir,
-				       DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	desc = dmaengine_prep_config_sg(dma->chan, dma->sg, dma->sg_len, dir,
+					DMA_PREP_INTERRUPT | DMA_CTRL_ACK,
+					&config);
 	if (!desc)
 		return -ENOMEM;
 

-- 
2.34.1

Re: [PATCH v2 1/8] dmaengine: Add API to combine configuration and preparation (sg and single)

[Damien Le Moal]

On 12/19/25 00:56, Frank Li wrote:
> Previously, configuration and preparation required two separate calls. This
> works well when configuration is done only once during initialization.
> 
> However, in cases where the burst length or source/destination address must
> be adjusted for each transfer, calling two functions is verbose and
> requires additional locking to ensure both steps complete atomically.
> 
> Add a new API dmaengine_prep_config_single() and dmaengine_prep_config_sg()
> and callback device_prep_config_sg() that combines configuration and
> preparation into a single operation. If the configuration argument is
> passed as NULL, fall back to the existing implementation.
> 
> Add a new API dmaengine_prep_config_single_safe() and
> dmaengine_prep_config_sg_safe() for re-entrancy, which require driver
> implement callback device_prep_config_sg().
> 
> Tested-by: Niklas Cassel <cassel@kernel.org>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
> change in v2
> - add () for function
> - use short name device_prep_sg(), remove "slave" and "config". the 'slave'
> is reduntant. after remove slave, the function name is difference existed
> one, so remove _config suffix.
> ---
>  Documentation/driver-api/dmaengine/client.rst |   9 +++
>  include/linux/dmaengine.h                     | 103 ++++++++++++++++++++++++--
>  2 files changed, 105 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/driver-api/dmaengine/client.rst b/Documentation/driver-api/dmaengine/client.rst
> index d491e385d61a98b8a804cd823caf254a2dc62cf4..02c45b7d7a779421411eb9c68325cdedafcfe3b1 100644
> --- a/Documentation/driver-api/dmaengine/client.rst
> +++ b/Documentation/driver-api/dmaengine/client.rst
> @@ -80,6 +80,10 @@ The details of these operations are:
>  
>    - slave_sg: DMA a list of scatter gather buffers from/to a peripheral
>  
> +  - config_sg: Similar with slave_sg, just pass down dma_slave_config
> +    struct to avoid call dmaengine_slave_config() every time if need

...struct to avoid calling dmaengine_slave_config() every time adjusting the
burst length or the FIFO address is needed.

> +    adjust burst length or FIFO address.
> +

> +static inline struct dma_async_tx_descriptor *
> +dmaengine_prep_config_single_safe(struct dma_chan *chan, dma_addr_t buf,
> +	size_t len, enum dma_transfer_direction dir, unsigned long flags,
> +	struct dma_slave_config *config)
>  {
>  	struct scatterlist sg;
> +
>  	sg_init_table(&sg, 1);
>  	sg_dma_address(&sg) = buf;
>  	sg_dma_len(&sg) = len;
>  
> -	if (!chan || !chan->device || !chan->device->device_prep_slave_sg)
> +	if (!chan || !chan->device || !chan->device->device_prep_config_sg)
> +		return NULL;

While at it, please move this arguments check before the sg initialization.
Otherwise, this is a little odd (argument checks generally are done first).

> +
> +	return chan->device->device_prep_config_sg(chan, &sg, 1, dir,
> +						   flags, config, NULL);
> +}
> +
> +static inline struct dma_async_tx_descriptor *
> +dmaengine_prep_config_single(struct dma_chan *chan, dma_addr_t buf, size_t len,
> +	enum dma_transfer_direction dir, unsigned long flags,
> +	struct dma_slave_config *config)
> +{
> +	struct scatterlist sg;
> +
> +	sg_init_table(&sg, 1);
> +	sg_dma_address(&sg) = buf;
> +	sg_dma_len(&sg) = len;
> +
> +	if (!chan || !chan->device)
> +		return NULL;

Same here. Check these before initializing sg.

> +
> +	if (chan->device->device_prep_config_sg)
> +		return dmaengine_prep_config_sg_safe(chan, &sg, 1, dir,
> +						     flags, config);
> +
> +	if (config)
> +		if (dmaengine_slave_config(chan, config))
> +			return NULL;
> +
> +	if (!chan->device->device_prep_slave_sg)
>  		return NULL;
>  
>  	return chan->device->device_prep_slave_sg(chan, &sg, 1,
>  						  dir, flags, NULL);
>  }
>  
> +static inline struct dma_async_tx_descriptor *
> +dmaengine_prep_slave_single(struct dma_chan *chan, dma_addr_t buf, size_t len,
> +			    enum dma_transfer_direction dir,
> +			    unsigned long flags)
> +{
> +	return dmaengine_prep_config_single(chan, buf, len, dir, flags, NULL);
> +}
> +
>  /**
>   * dmaengine_prep_peripheral_dma_vec() - Prepare a DMA scatter-gather descriptor
>   * @chan: The channel to be used for this descriptor
> @@ -1009,17 +1079,36 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_peripheral_dma_vec(
>  							    dir, flags);
>  }
>  
> -static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_sg(
> +static inline struct dma_async_tx_descriptor *dmaengine_prep_config_sg(

Very odd line split. Please split this after the "*" of the return type.

>  	struct dma_chan *chan, struct scatterlist *sgl,	unsigned int sg_len,
> -	enum dma_transfer_direction dir, unsigned long flags)
> +	enum dma_transfer_direction dir, unsigned long flags,
> +	struct dma_slave_config *config)
>  {
> -	if (!chan || !chan->device || !chan->device->device_prep_slave_sg)
> +	if (!chan || !chan->device)
> +		return NULL;
> +
> +	if (chan->device->device_prep_config_sg)
> +		return dmaengine_prep_config_sg_safe(chan, sgl, sg_len,
> +					dir, flags, config);
> +
> +	if (config)
> +		if (dmaengine_slave_config(chan, config))
> +			return NULL;
> +
> +	if (!chan->device->device_prep_slave_sg)
>  		return NULL;
>  
>  	return chan->device->device_prep_slave_sg(chan, sgl, sg_len,
>  						  dir, flags, NULL);
>  }
>  
> +static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_sg(

Same comment here.

> +	struct dma_chan *chan, struct scatterlist *sgl, unsigned int sg_len,
> +	enum dma_transfer_direction dir, unsigned long flags)
> +{
> +	return dmaengine_prep_config_sg(chan, sgl, sg_len, dir, flags, NULL);
> +}
> +
>  #ifdef CONFIG_RAPIDIO_DMA_ENGINE
>  struct rio_dma_ext;
>  static inline struct dma_async_tx_descriptor *dmaengine_prep_rio_sg(
> 


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH v2 2/8] PCI: endpoint: pci-epf-test: Use dmaenigne_prep_config_single() to simplify code

[Damien Le Moal]

On 12/19/25 00:56, Frank Li wrote:
> Use dmaenigne_prep_config_single() to simplify code.
> 
> No functional change.
> 
> Tested-by: Niklas Cassel <cassel@kernel.org>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>

Looks good.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

-- 
Damien Le Moal
Western Digital Research

Re: [PATCH v2 3/8] dmaengine: dw-edma: Use new .device_prep_config_sg() callback

[Damien Le Moal]

On 12/19/25 00:56, Frank Li wrote:
> Use the new .device_prep_config_sg() callback to combine configuration and
> descriptor preparation.
> 
> No functional changes.
> 
> Tested-by: Niklas Cassel <cassel@kernel.org>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>

Looks good.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

-- 
Damien Le Moal
Western Digital Research

Re: [PATCH v2 4/8] dmaengine: dw-edma: Pass dma_slave_config to dw_edma_device_transfer()

[Damien Le Moal]

On 12/19/25 00:56, Frank Li wrote:
> Pass dma_slave_config to dw_edma_device_transfer() to support atomic
> configuration and descriptor preparation when a non-NULL config is
> provided to device_prep_config_sg().
> 
> Tested-by: Niklas Cassel <cassel@kernel.org>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
>  drivers/dma/dw-edma/dw-edma-core.c | 22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> index e005b7bdaee156a3f4573b4734f50e3e47553dd2..1863254bf61eb892cb0cf8934e53b40d32027dfa 100644
> --- a/drivers/dma/dw-edma/dw-edma-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-core.c
> @@ -230,6 +230,15 @@ static int dw_edma_device_config(struct dma_chan *dchan,
>  	return 0;
>  }
>  
> +static struct dma_slave_config *
> +dw_edma_device_get_config(struct dma_chan *dchan,
> +			  struct dma_slave_config *config)
> +{
> +	struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
> +
> +	return config ? config : &chan->config;
> +}

I would rewrite this as:

static struct dma_slave_config *
dw_edma_device_get_config(struct dma_chan *dchan,
			  struct dma_slave_config *config)
{
	struct dw_edma_chan *chan;

	if (config)
		return config;

	chan = dchan2dw_edma_chan(dchan);

	return &chan->config;
}

That avoids the call to dchan2dw_edma_chan() if config is specified.

-- 
Damien Le Moal
Western Digital Research

Re: [PATCH v2 5/8] nvmet: pci-epf: Remove unnecessary dmaengine_terminate_sync() on each DMA transfer

[Damien Le Moal]

On 12/19/25 00:56, Frank Li wrote:
> dmaengine_terminate_sync() cancels all pending requests. Calling it for
> every DMA transfer is unnecessary and counterproductive. This function is
> generally intended for cleanup paths such as module removal, device close,
> or unbind operations.
> 
> Remove the redundant calls for success path and keep it only at error path.
> 
> Tested-by: Niklas Cassel <cassel@kernel.org>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>

Looks good.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

-- 
Damien Le Moal
Western Digital Research

Re: [PATCH v2 6/8] nvmet: pci-epf: Use dmaengine_prep_config_single_safe() API

[Damien Le Moal]

On 12/19/25 00:56, Frank Li wrote:
> Use the new dmaengine_prep_config_single_safe() API to combine the
> configuration and descriptor preparation into a single call.
> 
> Since dmaengine_prep_config_single_safe() performs the configuration and
> preparation atomically and dw edma driver implement prep_config_sg() call
> back, so dmaengine_prep_config_single() is reentriable, the mutex can be
> removed.

What about for platforms other than DesignWare EDMA ?
This is a generic endpoint driver that can work on any platform that is endpoint
capable and that has a DMA channel for the PCI endpoint.

The dmaengine_prep_config_single_safe() API should be handling everything
transparently for any platform, regardless of the DMA channel driver
implementing or not the prep_config_sg() callback.

For platforms that do not implement it, I suspect that the mutex will still be
needed here. So how to we resolve this ? Ideally, all of that should be hidden
by the DMA API. The endpoint driver should not need to deal with these differences.

> 
> Tested-by: Niklas Cassel <cassel@kernel.org>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
>  drivers/nvme/target/pci-epf.c | 18 ++++--------------
>  1 file changed, 4 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/nvme/target/pci-epf.c b/drivers/nvme/target/pci-epf.c
> index 56b1c6a7706a9e2dd9d8aaf17b440129b948486c..8b5ea5d4c79dfd461b767cfd4033a9e4604c94b1 100644
> --- a/drivers/nvme/target/pci-epf.c
> +++ b/drivers/nvme/target/pci-epf.c
> @@ -388,22 +388,15 @@ static int nvmet_pci_epf_dma_transfer(struct nvmet_pci_epf *nvme_epf,
>  		return -EINVAL;
>  	}
>  
> -	mutex_lock(lock);
> -
>  	dma_dev = dmaengine_get_dma_device(chan);
>  	dma_addr = dma_map_single(dma_dev, seg->buf, seg->length, dir);
>  	ret = dma_mapping_error(dma_dev, dma_addr);
>  	if (ret)
> -		goto unlock;
> -
> -	ret = dmaengine_slave_config(chan, &sconf);
> -	if (ret) {
> -		dev_err(dev, "Failed to configure DMA channel\n");
> -		goto unmap;
> -	}
> +		return ret;
>  
> -	desc = dmaengine_prep_slave_single(chan, dma_addr, seg->length,
> -					   sconf.direction, DMA_CTRL_ACK);
> +	desc = dmaengine_prep_config_single_safe(chan, dma_addr, seg->length,
> +						 sconf.direction,
> +						 DMA_CTRL_ACK, &sconf);
>  	if (!desc) {
>  		dev_err(dev, "Failed to prepare DMA\n");
>  		ret = -EIO;
> @@ -426,9 +419,6 @@ static int nvmet_pci_epf_dma_transfer(struct nvmet_pci_epf *nvme_epf,
>  unmap:
>  	dma_unmap_single(dma_dev, dma_addr, seg->length, dir);
>  
> -unlock:
> -	mutex_unlock(lock);
> -
>  	return ret;
>  }
>  
> 


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH v2 1/8] dmaengine: Add API to combine configuration and preparation (sg and single)

[Vinod Koul]

On 18-12-25, 10:56, Frank Li wrote:
> Previously, configuration and preparation required two separate calls. This
> works well when configuration is done only once during initialization.
> 
> However, in cases where the burst length or source/destination address must
> be adjusted for each transfer, calling two functions is verbose and
> requires additional locking to ensure both steps complete atomically.
> 
> Add a new API dmaengine_prep_config_single() and dmaengine_prep_config_sg()
> and callback device_prep_config_sg() that combines configuration and
> preparation into a single operation. If the configuration argument is
> passed as NULL, fall back to the existing implementation.
> 
> Add a new API dmaengine_prep_config_single_safe() and
> dmaengine_prep_config_sg_safe() for re-entrancy, which require driver
> implement callback device_prep_config_sg().
> 
> Tested-by: Niklas Cassel <cassel@kernel.org>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
> change in v2
> - add () for function
> - use short name device_prep_sg(), remove "slave" and "config". the 'slave'
> is reduntant. after remove slave, the function name is difference existed
> one, so remove _config suffix.
> ---
>  Documentation/driver-api/dmaengine/client.rst |   9 +++
>  include/linux/dmaengine.h                     | 103 ++++++++++++++++++++++++--
>  2 files changed, 105 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/driver-api/dmaengine/client.rst b/Documentation/driver-api/dmaengine/client.rst
> index d491e385d61a98b8a804cd823caf254a2dc62cf4..02c45b7d7a779421411eb9c68325cdedafcfe3b1 100644
> --- a/Documentation/driver-api/dmaengine/client.rst
> +++ b/Documentation/driver-api/dmaengine/client.rst
> @@ -80,6 +80,10 @@ The details of these operations are:
>  
>    - slave_sg: DMA a list of scatter gather buffers from/to a peripheral
>  
> +  - config_sg: Similar with slave_sg, just pass down dma_slave_config
> +    struct to avoid call dmaengine_slave_config() every time if need
> +    adjust burst length or FIFO address.
> +
>    - peripheral_dma_vec: DMA an array of scatter gather buffers from/to a
>      peripheral. Similar to slave_sg, but uses an array of dma_vec
>      structures instead of a scatterlist.
> @@ -106,6 +110,11 @@ The details of these operations are:
>  		unsigned int sg_len, enum dma_data_direction direction,
>  		unsigned long flags);
>  
> +     struct dma_async_tx_descriptor *dmaengine_prep_config_sg(
> +		struct dma_chan *chan, struct scatterlist *sgl,
> +		unsigned int sg_len, enum dma_transfer_direction dir,
> +		unsigned long flags, struct dma_slave_config *config);
> +
>       struct dma_async_tx_descriptor *dmaengine_prep_peripheral_dma_vec(
>  		struct dma_chan *chan, const struct dma_vec *vecs,
>  		size_t nents, enum dma_data_direction direction,
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index 99efe2b9b4ea9844ca6161208362ef18ef111d96..276dca760f95e1131f5ff5bf69752c4c9cb1bcad 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -835,6 +835,8 @@ struct dma_filter {
>   *	where the address and size of each segment is located in one entry of
>   *	the dma_vec array.
>   * @device_prep_slave_sg: prepares a slave dma operation
> + *	(Deprecated, use @device_prep_config_sg)

Sorry that is _not_ deprecated, we are adding another way to do this in
a single shot

> + * @device_prep_config_sg: prepares a slave DMA operation with dma_slave_config
>   * @device_prep_dma_cyclic: prepare a cyclic dma operation suitable for audio.
>   *	The function takes a buffer of size buf_len. The callback function will
>   *	be called after period_len bytes have been transferred.
> @@ -934,6 +936,11 @@ struct dma_device {
>  		struct dma_chan *chan, struct scatterlist *sgl,
>  		unsigned int sg_len, enum dma_transfer_direction direction,
>  		unsigned long flags, void *context);
> +	struct dma_async_tx_descriptor *(*device_prep_config_sg)(
> +		struct dma_chan *chan, struct scatterlist *sgl,
> +		unsigned int sg_len, enum dma_transfer_direction direction,
> +		unsigned long flags, struct dma_slave_config *config,
> +		void *context);
>  	struct dma_async_tx_descriptor *(*device_prep_dma_cyclic)(
>  		struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
>  		size_t period_len, enum dma_transfer_direction direction,
> @@ -974,22 +981,85 @@ static inline bool is_slave_direction(enum dma_transfer_direction direction)
>  	       (direction == DMA_DEV_TO_DEV);
>  }
>  
> -static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_single(
> -	struct dma_chan *chan, dma_addr_t buf, size_t len,
> -	enum dma_transfer_direction dir, unsigned long flags)
> +/*
> + * Re-entrancy and locking considerations for callers:
> + *
> + * dmaengine_prep_config_single(sg)_safe() is re-entrant and requires the
> + * DMA engine driver to implement device_prep_config_sg(). It returns NULL
> + * if device_prep_config_sg() is not implemented.
> + *
> + * The unsafe variant (without the _safe suffix) falls back to calling
> + * dmaengine_slave_config() and dmaengine_prep_slave_sg() separately.
> + * In this case, additional locking may be required, depending on the
> + * DMA consumer's usage.
> + */
> +static inline struct dma_async_tx_descriptor *
> +dmaengine_prep_config_sg_safe(struct dma_chan *chan, struct scatterlist *sgl,
> +	unsigned int sg_len, enum dma_transfer_direction dir,
> +	unsigned long flags, struct dma_slave_config *config)
> +{
> +	if (!chan || !chan->device || !chan->device->device_prep_config_sg)
> +		return NULL;
> +
> +	return chan->device->device_prep_config_sg(chan, sgl, sg_len,
> +						   dir, flags, config, NULL);
> +}
> +
> +static inline struct dma_async_tx_descriptor *
> +dmaengine_prep_config_single_safe(struct dma_chan *chan, dma_addr_t buf,
> +	size_t len, enum dma_transfer_direction dir, unsigned long flags,
> +	struct dma_slave_config *config)

Agree with Damien, this could look better!

-- 
~Vinod