[PATCH] dmaengine: Remove DMA_MEMCPY_SG operation as it has no consumers

[Adrian Larumbe <adrian.larumbe@collabora.com>]

There are no in kernel consumers for DMA_MEMCPY_SG. Remove operation and
Xilinx CDMA driver code which implemented it.

This reverts the following commits:

- commit 58fe10766048 ("dmaengine: Add documentation for new memcpy
scatter-gather function")
- commit 3218910fd585 ("dmaengine: Add core function and capability check
for DMA_MEMCPY_SG")
- commit 29cf37fa6dd9 ("dmaengine: Add consumer for the new DMA_MEMCPY_SG
API function.")

Signed-off-by: Adrian Larumbe <adrian.larumbe@collabora.com>
---
 .../driver-api/dmaengine/provider.rst         |  23 ----
 drivers/dma/dmaengine.c                       |   7 -
 drivers/dma/xilinx/xilinx_dma.c               | 122 ------------------
 include/linux/dmaengine.h                     |  20 ---
 4 files changed, 172 deletions(-)

diff --git a/Documentation/driver-api/dmaengine/provider.rst b/Documentation/driver-api/dmaengine/provider.rst
index 1e0f1f85d10e..8cf704332bb4 100644
--- a/Documentation/driver-api/dmaengine/provider.rst
+++ b/Documentation/driver-api/dmaengine/provider.rst
@@ -162,29 +162,6 @@ Currently, the types available are:
 
   - The device is able to do memory to memory copies
 
-- - DMA_MEMCPY_SG
-
-  - The device supports memory to memory scatter-gather transfers.
-
-  - Even though a plain memcpy can look like a particular case of a
-    scatter-gather transfer, with a single chunk to copy, it's a distinct
-    transaction type in the mem2mem transfer case. This is because some very
-    simple devices might be able to do contiguous single-chunk memory copies,
-    but have no support for more complex SG transfers.
-
-  - No matter what the overall size of the combined chunks for source and
-    destination is, only as many bytes as the smallest of the two will be
-    transmitted. That means the number and size of the scatter-gather buffers in
-    both lists need not be the same, and that the operation functionally is
-    equivalent to a ``strncpy`` where the ``count`` argument equals the smallest
-    total size of the two scatter-gather list buffers.
-
-  - It's usually used for copying pixel data between host memory and
-    memory-mapped GPU device memory, such as found on modern PCI video graphics
-    cards. The most immediate example is the OpenGL API function
-    ``glReadPielx()``, which might require a verbatim copy of a huge framebuffer
-    from local device memory onto host memory.
-
 - DMA_XOR
 
   - The device is able to perform XOR operations on memory areas
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index e80feeea0e01..c741b6431958 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -1153,13 +1153,6 @@ int dma_async_device_register(struct dma_device *device)
 		return -EIO;
 	}
 
-	if (dma_has_cap(DMA_MEMCPY_SG, device->cap_mask) && !device->device_prep_dma_memcpy_sg) {
-		dev_err(device->dev,
-			"Device claims capability %s, but op is not defined\n",
-			"DMA_MEMCPY_SG");
-		return -EIO;
-	}
-
 	if (dma_has_cap(DMA_XOR, device->cap_mask) && !device->device_prep_dma_xor) {
 		dev_err(device->dev,
 			"Device claims capability %s, but op is not defined\n",
diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index cd62bbb50e8b..6276934d4d2b 100644
--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c
@@ -2127,126 +2127,6 @@ xilinx_cdma_prep_memcpy(struct dma_chan *dchan, dma_addr_t dma_dst,
 	return NULL;
 }
 
-/**
- * xilinx_cdma_prep_memcpy_sg - prepare descriptors for a memcpy_sg transaction
- * @dchan: DMA channel
- * @dst_sg: Destination scatter list
- * @dst_sg_len: Number of entries in destination scatter list
- * @src_sg: Source scatter list
- * @src_sg_len: Number of entries in source scatter list
- * @flags: transfer ack flags
- *
- * Return: Async transaction descriptor on success and NULL on failure
- */
-static struct dma_async_tx_descriptor *xilinx_cdma_prep_memcpy_sg(
-			struct dma_chan *dchan, struct scatterlist *dst_sg,
-			unsigned int dst_sg_len, struct scatterlist *src_sg,
-			unsigned int src_sg_len, unsigned long flags)
-{
-	struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
-	struct xilinx_dma_tx_descriptor *desc;
-	struct xilinx_cdma_tx_segment *segment, *prev = NULL;
-	struct xilinx_cdma_desc_hw *hw;
-	size_t len, dst_avail, src_avail;
-	dma_addr_t dma_dst, dma_src;
-
-	if (unlikely(dst_sg_len == 0 || src_sg_len == 0))
-		return NULL;
-
-	if (unlikely(!dst_sg  || !src_sg))
-		return NULL;
-
-	desc = xilinx_dma_alloc_tx_descriptor(chan);
-	if (!desc)
-		return NULL;
-
-	dma_async_tx_descriptor_init(&desc->async_tx, &chan->common);
-	desc->async_tx.tx_submit = xilinx_dma_tx_submit;
-
-	dst_avail = sg_dma_len(dst_sg);
-	src_avail = sg_dma_len(src_sg);
-	/*
-	 * loop until there is either no more source or no more destination
-	 * scatterlist entry
-	 */
-	while (true) {
-		len = min_t(size_t, src_avail, dst_avail);
-		len = min_t(size_t, len, chan->xdev->max_buffer_len);
-		if (len == 0)
-			goto fetch;
-
-		/* Allocate the link descriptor from DMA pool */
-		segment = xilinx_cdma_alloc_tx_segment(chan);
-		if (!segment)
-			goto error;
-
-		dma_dst = sg_dma_address(dst_sg) + sg_dma_len(dst_sg) -
-			dst_avail;
-		dma_src = sg_dma_address(src_sg) + sg_dma_len(src_sg) -
-			src_avail;
-		hw = &segment->hw;
-		hw->control = len;
-		hw->src_addr = dma_src;
-		hw->dest_addr = dma_dst;
-		if (chan->ext_addr) {
-			hw->src_addr_msb = upper_32_bits(dma_src);
-			hw->dest_addr_msb = upper_32_bits(dma_dst);
-		}
-
-		if (prev) {
-			prev->hw.next_desc = segment->phys;
-			if (chan->ext_addr)
-				prev->hw.next_desc_msb =
-					upper_32_bits(segment->phys);
-		}
-
-		prev = segment;
-		dst_avail -= len;
-		src_avail -= len;
-		list_add_tail(&segment->node, &desc->segments);
-
-fetch:
-		/* Fetch the next dst scatterlist entry */
-		if (dst_avail == 0) {
-			if (dst_sg_len == 0)
-				break;
-			dst_sg = sg_next(dst_sg);
-			if (dst_sg == NULL)
-				break;
-			dst_sg_len--;
-			dst_avail = sg_dma_len(dst_sg);
-		}
-		/* Fetch the next src scatterlist entry */
-		if (src_avail == 0) {
-			if (src_sg_len == 0)
-				break;
-			src_sg = sg_next(src_sg);
-			if (src_sg == NULL)
-				break;
-			src_sg_len--;
-			src_avail = sg_dma_len(src_sg);
-		}
-	}
-
-	if (list_empty(&desc->segments)) {
-		dev_err(chan->xdev->dev,
-			"%s: Zero-size SG transfer requested\n", __func__);
-		goto error;
-	}
-
-	/* Link the last hardware descriptor with the first. */
-	segment = list_first_entry(&desc->segments,
-				struct xilinx_cdma_tx_segment, node);
-	desc->async_tx.phys = segment->phys;
-	prev->hw.next_desc = segment->phys;
-
-	return &desc->async_tx;
-
-error:
-	xilinx_dma_free_tx_descriptor(chan, desc);
-	return NULL;
-}
-
 /**
  * xilinx_dma_prep_slave_sg - prepare descriptors for a DMA_SLAVE transaction
  * @dchan: DMA channel
@@ -3240,9 +3120,7 @@ static int xilinx_dma_probe(struct platform_device *pdev)
 					  DMA_RESIDUE_GRANULARITY_SEGMENT;
 	} else if (xdev->dma_config->dmatype == XDMA_TYPE_CDMA) {
 		dma_cap_set(DMA_MEMCPY, xdev->common.cap_mask);
-		dma_cap_set(DMA_MEMCPY_SG, xdev->common.cap_mask);
 		xdev->common.device_prep_dma_memcpy = xilinx_cdma_prep_memcpy;
-		xdev->common.device_prep_dma_memcpy_sg = xilinx_cdma_prep_memcpy_sg;
 		/* Residue calculation is supported by only AXI DMA and CDMA */
 		xdev->common.residue_granularity =
 					  DMA_RESIDUE_GRANULARITY_SEGMENT;
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index b46b88e6aa0d..c923f4e60f24 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -50,7 +50,6 @@ enum dma_status {
  */
 enum dma_transaction_type {
 	DMA_MEMCPY,
-	DMA_MEMCPY_SG,
 	DMA_XOR,
 	DMA_PQ,
 	DMA_XOR_VAL,
@@ -887,11 +886,6 @@ struct dma_device {
 	struct dma_async_tx_descriptor *(*device_prep_dma_memcpy)(
 		struct dma_chan *chan, dma_addr_t dst, dma_addr_t src,
 		size_t len, unsigned long flags);
-	struct dma_async_tx_descriptor *(*device_prep_dma_memcpy_sg)(
-		struct dma_chan *chan,
-		struct scatterlist *dst_sg, unsigned int dst_nents,
-		struct scatterlist *src_sg, unsigned int src_nents,
-		unsigned long flags);
 	struct dma_async_tx_descriptor *(*device_prep_dma_xor)(
 		struct dma_chan *chan, dma_addr_t dst, dma_addr_t *src,
 		unsigned int src_cnt, size_t len, unsigned long flags);
@@ -1060,20 +1054,6 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_dma_memcpy(
 						    len, flags);
 }
 
-static inline struct dma_async_tx_descriptor *dmaengine_prep_dma_memcpy_sg(
-		struct dma_chan *chan,
-		struct scatterlist *dst_sg, unsigned int dst_nents,
-		struct scatterlist *src_sg, unsigned int src_nents,
-		unsigned long flags)
-{
-	if (!chan || !chan->device || !chan->device->device_prep_dma_memcpy_sg)
-		return NULL;
-
-	return chan->device->device_prep_dma_memcpy_sg(chan, dst_sg, dst_nents,
-						       src_sg, src_nents,
-						       flags);
-}
-
 static inline bool dmaengine_is_metadata_mode_supported(struct dma_chan *chan,
 		enum dma_desc_metadata_mode mode)
 {
-- 
2.37.0