[PATCH v7 09/10] dmaengine: dw-edma: Use burst array instead of linked list

From: Frank Li <[email protected]>

The current descriptor layout is:

  struct dw_edma_desc *desc
   └─ chunk list
        └─ burst list

Creating a DMA descriptor requires at least three kzalloc() calls because
each burst is allocated as a linked-list node. Since the number of bursts
is already known when the descriptor is created, a linked list is not
necessary.

Allocate a burst array when creating each chunk to simplify the code and
eliminate one kzalloc() call.

Tested-by: Koichiro Den <[email protected]>
Tested-By: Devendra Verma <[email protected]>
Signed-off-by: Frank Li <[email protected]>
---
Change in v7
- One more place, use bursts_max instead of chan->ll_max because non-ll
mode only allow 1 burst pre-transfer. Found by sashiko AI.

change in v6
- use bursts_max instead of chan->ll_max because non-ll mode only allow
1 burst pre-transfer. Found by sashiko AI.

change in v4
- collect Koichiro tag
---
 drivers/dma/dw-edma/dw-edma-core.c | 120 +++++++------------------------------
 drivers/dma/dw-edma/dw-edma-core.h |   9 +--
 2 files changed, 26 insertions(+), 103 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index f52d9fd18e573..c028011cc61ca 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -40,38 +40,15 @@ u64 dw_edma_get_pci_address(struct dw_edma_chan *chan, phys_addr_t cpu_addr)
 	return cpu_addr;
 }
 
-static struct dw_edma_burst *dw_edma_alloc_burst(struct dw_edma_chunk *chunk)
-{
-	struct dw_edma_burst *burst;
-
-	burst = kzalloc_obj(*burst, GFP_NOWAIT);
-	if (unlikely(!burst))
-		return NULL;
-
-	INIT_LIST_HEAD(&burst->list);
-	if (chunk->burst) {
-		/* Create and add new element into the linked list */
-		chunk->bursts_alloc++;
-		list_add_tail(&burst->list, &chunk->burst->list);
-	} else {
-		/* List head */
-		chunk->bursts_alloc = 0;
-		chunk->burst = burst;
-	}
-
-	return burst;
-}
-
-static struct dw_edma_chunk *dw_edma_alloc_chunk(struct dw_edma_desc *desc)
+static struct dw_edma_chunk *dw_edma_alloc_chunk(struct dw_edma_desc *desc, u32 nburst)
 {
 	struct dw_edma_chan *chan = desc->chan;
 	struct dw_edma_chunk *chunk;
 
-	chunk = kzalloc_obj(*chunk, GFP_NOWAIT);
+	chunk = kzalloc_flex(*chunk, burst, nburst, GFP_NOWAIT);
 	if (unlikely(!chunk))
 		return NULL;
 
-	INIT_LIST_HEAD(&chunk->list);
 	chunk->chan = chan;
 	/* Toggling change bit (CB) in each chunk, this is a mechanism to
 	 * inform the eDMA HW block that this is a new linked list ready
@@ -81,20 +58,10 @@ static struct dw_edma_chunk *dw_edma_alloc_chunk(struct dw_edma_desc *desc)
 	 */
 	chunk->cb = !(desc->chunks_alloc % 2);
 
-	if (desc->chunk) {
-		/* Create and add new element into the linked list */
-		if (!dw_edma_alloc_burst(chunk)) {
-			kfree(chunk);
-			return NULL;
-		}
-		desc->chunks_alloc++;
-		list_add_tail(&chunk->list, &desc->chunk->list);
-	} else {
-		/* List head */
-		chunk->burst = NULL;
-		desc->chunks_alloc = 0;
-		desc->chunk = chunk;
-	}
+	chunk->nburst = nburst;
+
+	list_add_tail(&chunk->list, &desc->chunk_list);
+	desc->chunks_alloc++;
 
 	return chunk;
 }
@@ -108,53 +75,23 @@ static struct dw_edma_desc *dw_edma_alloc_desc(struct dw_edma_chan *chan)
 		return NULL;
 
 	desc->chan = chan;
-	if (!dw_edma_alloc_chunk(desc)) {
-		kfree(desc);
-		return NULL;
-	}
 
-	return desc;
-}
+	INIT_LIST_HEAD(&desc->chunk_list);
 
-static void dw_edma_free_burst(struct dw_edma_chunk *chunk)
-{
-	struct dw_edma_burst *child, *_next;
-
-	/* Remove all the list elements */
-	list_for_each_entry_safe(child, _next, &chunk->burst->list, list) {
-		list_del(&child->list);
-		kfree(child);
-		chunk->bursts_alloc--;
-	}
-
-	/* Remove the list head */
-	kfree(child);
-	chunk->burst = NULL;
+	return desc;
 }
 
-static void dw_edma_free_chunk(struct dw_edma_desc *desc)
+static void dw_edma_free_desc(struct dw_edma_desc *desc)
 {
 	struct dw_edma_chunk *child, *_next;
 
-	if (!desc->chunk)
-		return;
-
 	/* Remove all the list elements */
-	list_for_each_entry_safe(child, _next, &desc->chunk->list, list) {
-		dw_edma_free_burst(child);
+	list_for_each_entry_safe(child, _next, &desc->chunk_list, list) {
 		list_del(&child->list);
 		kfree(child);
 		desc->chunks_alloc--;
 	}
 
-	/* Remove the list head */
-	kfree(child);
-	desc->chunk = NULL;
-}
-
-static void dw_edma_free_desc(struct dw_edma_desc *desc)
-{
-	dw_edma_free_chunk(desc);
 	kfree(desc);
 }
 
@@ -166,23 +103,17 @@ static void vchan_free_desc(struct virt_dma_desc *vdesc)
 static void dw_edma_core_start(struct dw_edma_chunk *chunk, bool first)
 {
 	struct dw_edma_chan *chan = chunk->chan;
-	struct dw_edma_burst *child;
 	u32 i = 0;
-	int j;
 
 	if (chan->non_ll) {
-		child = list_first_entry_or_null(&chunk->burst->list,
-						 struct dw_edma_burst, list);
-		if (child)
-			chan->dw->core->non_ll_start(chunk->chan, child);
+		if (chunk->nburst == 1)
+			chan->dw->core->non_ll_start(chunk->chan, &chunk->burst[0]);
 		return;
 	}
 
-	j = chunk->bursts_alloc;
-	list_for_each_entry(child, &chunk->burst->list, list) {
-		j--;
-		dw_edma_core_ll_data(chan, child, i++, chunk->cb, !j);
-	}
+	for (i = 0; i < chunk->nburst; i++)
+		dw_edma_core_ll_data(chan, &chunk->burst[i], i, chunk->cb,
+				     i == chunk->nburst - 1);
 
 	dw_edma_core_ll_link(chan, i, chunk->cb, chan->ll_region.paddr);
 
@@ -206,14 +137,13 @@ static int dw_edma_start_transfer(struct dw_edma_chan *chan)
 	if (!desc)
 		return 0;
 
-	child = list_first_entry_or_null(&desc->chunk->list,
+	child = list_first_entry_or_null(&desc->chunk_list,
 					 struct dw_edma_chunk, list);
 	if (!child)
 		return 0;
 
 	dw_edma_core_start(child, !desc->xfer_sz);
 	desc->xfer_sz += child->xfer_sz;
-	dw_edma_free_burst(child);
 	list_del(&child->list);
 	kfree(child);
 	desc->chunks_alloc--;
@@ -425,14 +355,14 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer,
 	struct dw_edma_chan *chan = dchan2dw_edma_chan(xfer->dchan);
 	enum dma_transfer_direction dir = xfer->direction;
 	struct scatterlist *sg = NULL;
-	struct dw_edma_chunk *chunk;
+	struct dw_edma_chunk *chunk = NULL;
 	struct dw_edma_burst *burst;
 	struct dw_edma_desc *desc;
 	u64 src_addr, dst_addr;
 	size_t fsz = 0;
 	u32 bursts_max;
 	u32 cnt = 0;
-	int i;
+	u32 i;
 
 	if (!chan->configured)
 		return NULL;
@@ -499,10 +429,6 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer,
 	if (unlikely(!desc))
 		goto err_alloc;
 
-	chunk = dw_edma_alloc_chunk(desc);
-	if (unlikely(!chunk))
-		goto err_alloc;
-
 	if (xfer->type == EDMA_XFER_INTERLEAVED) {
 		src_addr = xfer->xfer.il->src_start;
 		dst_addr = xfer->xfer.il->dst_start;
@@ -530,15 +456,15 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer,
 		if (xfer->type == EDMA_XFER_SCATTER_GATHER && !sg)
 			break;
 
-		if (chunk->bursts_alloc == bursts_max) {
-			chunk = dw_edma_alloc_chunk(desc);
+		if (!(i % bursts_max)) {
+			u32 n = min(cnt - i, bursts_max);
+
+			chunk = dw_edma_alloc_chunk(desc, n);
 			if (unlikely(!chunk))
 				goto err_alloc;
 		}
 
-		burst = dw_edma_alloc_burst(chunk);
-		if (unlikely(!burst))
-			goto err_alloc;
+		burst = chunk->burst + (i % bursts_max);
 
 		if (xfer->type == EDMA_XFER_CYCLIC)
 			burst->sz = xfer->xfer.cyclic.len;
diff --git a/drivers/dma/dw-edma/dw-edma-core.h b/drivers/dma/dw-edma/dw-edma-core.h
index 27415f3a2d04b..4950c57fca34f 100644
--- a/drivers/dma/dw-edma/dw-edma-core.h
+++ b/drivers/dma/dw-edma/dw-edma-core.h
@@ -43,7 +43,6 @@ struct dw_edma_chan;
 struct dw_edma_chunk;
 
 struct dw_edma_burst {
-	struct list_head		list;
 	u64				sar;
 	u64				dar;
 	u32				sz;
@@ -52,18 +51,16 @@ struct dw_edma_burst {
 struct dw_edma_chunk {
 	struct list_head		list;
 	struct dw_edma_chan		*chan;
-	struct dw_edma_burst		*burst;
-
-	u32				bursts_alloc;
-
 	u8				cb;
 	u32				xfer_sz;
+	u32                             nburst;
+	struct dw_edma_burst            burst[] __counted_by(nburst);
 };
 
 struct dw_edma_desc {
 	struct virt_dma_desc		vd;
 	struct dw_edma_chan		*chan;
-	struct dw_edma_chunk		*chunk;
+	struct list_head		chunk_list;
 
 	u32				chunks_alloc;
 

-- 
2.43.0