Dmaengine topic

- New device_prep_peripheral_dma_vec, documentation and user
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Merge tag 'dmaengine_topic_dma_vec' into next

Dmaengine topic
 - New device_prep_peripheral_dma_vec, documentation and user

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
 
+  - 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.
+
   - dma_cyclic: Perform a cyclic DMA operation from/to a peripheral till the
     operation is explicitly stopped.
 
@@ -102,6 +106,11 @@ 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_peripheral_dma_vec(
+		struct dma_chan *chan, const struct dma_vec *vecs,
+		size_t nents, enum dma_data_direction direction,
+		unsigned long flags);
+
      struct dma_async_tx_descriptor *dmaengine_prep_dma_cyclic(
 		struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
 		size_t period_len, enum dma_data_direction direction);

Documentation/driver-api/dmaengine/provider.rst

@@ -433,6 +433,12 @@ supported.
     - residue: Provides the residue bytes of the transfer for those that
       support residue.
 
+- ``device_prep_peripheral_dma_vec``
+
+  - Similar to ``device_prep_slave_sg``, but it takes a pointer to a
+    array of ``dma_vec`` structures, which (in the long run) will replace
+    scatterlists.
+
 - ``device_issue_pending``
 
   - Takes the first transaction descriptor in the pending queue,
@@ -544,6 +550,10 @@ dma_cookie_t
 - Not really relevant any more since the introduction of ``virt-dma``
   that abstracts it away.
 
+dma_vec
+
+- A small structure that contains a DMA address and length.
+
 DMA_CTRL_ACK
 
 - If clear, the descriptor cannot be reused by provider until the

drivers/dma/dma-axi-dmac.c

@@ -620,6 +620,45 @@ static struct axi_dmac_sg *axi_dmac_fill_linear_sg(struct axi_dmac_chan *chan,
 	return sg;
 }
 
+static struct dma_async_tx_descriptor *
+axi_dmac_prep_peripheral_dma_vec(struct dma_chan *c, const struct dma_vec *vecs,
+				 size_t nb, enum dma_transfer_direction direction,
+				 unsigned long flags)
+{
+	struct axi_dmac_chan *chan = to_axi_dmac_chan(c);
+	struct axi_dmac_desc *desc;
+	unsigned int num_sgs = 0;
+	struct axi_dmac_sg *dsg;
+	size_t i;
+
+	if (direction != chan->direction)
+		return NULL;
+
+	for (i = 0; i < nb; i++)
+		num_sgs += DIV_ROUND_UP(vecs[i].len, chan->max_length);
+
+	desc = axi_dmac_alloc_desc(chan, num_sgs);
+	if (!desc)
+		return NULL;
+
+	dsg = desc->sg;
+
+	for (i = 0; i < nb; i++) {
+		if (!axi_dmac_check_addr(chan, vecs[i].addr) ||
+		    !axi_dmac_check_len(chan, vecs[i].len)) {
+			kfree(desc);
+			return NULL;
+		}
+
+		dsg = axi_dmac_fill_linear_sg(chan, direction, vecs[i].addr, 1,
+					      vecs[i].len, dsg);
+	}
+
+	desc->cyclic = false;
+
+	return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
+}
+
 static struct dma_async_tx_descriptor *axi_dmac_prep_slave_sg(
 	struct dma_chan *c, struct scatterlist *sgl,
 	unsigned int sg_len, enum dma_transfer_direction direction,
@@ -1061,6 +1100,7 @@ static int axi_dmac_probe(struct platform_device *pdev)
 	dma_dev->device_tx_status = dma_cookie_status;
 	dma_dev->device_issue_pending = axi_dmac_issue_pending;
 	dma_dev->device_prep_slave_sg = axi_dmac_prep_slave_sg;
+	dma_dev->device_prep_peripheral_dma_vec = axi_dmac_prep_peripheral_dma_vec;
 	dma_dev->device_prep_dma_cyclic = axi_dmac_prep_dma_cyclic;
 	dma_dev->device_prep_interleaved_dma = axi_dmac_prep_interleaved;
 	dma_dev->device_terminate_all = axi_dmac_terminate_all;

include/linux/dmaengine.h

@@ -160,6 +160,16 @@ struct dma_interleaved_template {
 	struct data_chunk sgl[];
 };
 
+/**
+ * struct dma_vec - DMA vector
+ * @addr: Bus address of the start of the vector
+ * @len: Length in bytes of the DMA vector
+ */
+struct dma_vec {
+	dma_addr_t addr;
+	size_t len;
+};
+
 /**
  * enum dma_ctrl_flags - DMA flags to augment operation preparation,
  *  control completion, and communicate status.
@@ -910,6 +920,10 @@ struct dma_device {
 	struct dma_async_tx_descriptor *(*device_prep_dma_interrupt)(
 		struct dma_chan *chan, unsigned long flags);
 
+	struct dma_async_tx_descriptor *(*device_prep_peripheral_dma_vec)(
+		struct dma_chan *chan, const struct dma_vec *vecs,
+		size_t nents, enum dma_transfer_direction direction,
+		unsigned long flags);
 	struct dma_async_tx_descriptor *(*device_prep_slave_sg)(
 		struct dma_chan *chan, struct scatterlist *sgl,
 		unsigned int sg_len, enum dma_transfer_direction direction,
@@ -973,6 +987,25 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_single(
 						  dir, flags, NULL);
 }
 
+/**
+ * dmaengine_prep_peripheral_dma_vec() - Prepare a DMA scatter-gather descriptor
+ * @chan: The channel to be used for this descriptor
+ * @vecs: The array of DMA vectors that should be transferred
+ * @nents: The number of DMA vectors in the array
+ * @dir: Specifies the direction of the data transfer
+ * @flags: DMA engine flags
+ */
+static inline struct dma_async_tx_descriptor *dmaengine_prep_peripheral_dma_vec(
+	struct dma_chan *chan, const struct dma_vec *vecs, size_t nents,
+	enum dma_transfer_direction dir, unsigned long flags)
+{
+	if (!chan || !chan->device || !chan->device->device_prep_peripheral_dma_vec)
+		return NULL;
+
+	return chan->device->device_prep_peripheral_dma_vec(chan, vecs, nents,
+							    dir, flags);
+}
+
 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)