linux-kernel - [PATCH v5 1/6] dmaengine: sh: rz-dmac: Protect the driver specific lists

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Message-ID: <20251217135213.400280-2-claudiu.beznea.uj@bp.renesas.com>
Date: Wed, 17 Dec 2025 15:52:08 +0200
From: Claudiu <claudiu.beznea@...on.dev>
To: vkoul@...nel.org,
	fabrizio.castro.jz@...esas.com,
	biju.das.jz@...renesas.com,
	geert+renesas@...der.be,
	prabhakar.mahadev-lad.rj@...renesas.com
Cc: claudiu.beznea@...on.dev,
	dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
	stable@...r.kernel.org
Subject: [PATCH v5 1/6] dmaengine: sh: rz-dmac: Protect the driver specific lists

From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

The driver lists (ld_free, ld_queue) are used in
rz_dmac_free_chan_resources(), rz_dmac_terminate_all(),
rz_dmac_issue_pending(), and rz_dmac_irq_handler_thread(), all under
the virtual channel lock. Take the same lock in rz_dmac_prep_slave_sg()
and rz_dmac_prep_dma_memcpy() as well to avoid concurrency issues, since
these functions also check whether the lists are empty and update or
remove list entries.

Fixes: 5000d37042a6 ("dmaengine: sh: Add DMAC driver for RZ/G2L SoC")
Cc: stable@...r.kernel.org
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
---

Changes in v5:
- none, this patch is new

 drivers/dma/sh/rz-dmac.c | 57 ++++++++++++++++++++++------------------
 1 file changed, 32 insertions(+), 25 deletions(-)

diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c
index 9e5f088355e2..c8e3d9f77b8a 100644
--- a/drivers/dma/sh/rz-dmac.c
+++ b/drivers/dma/sh/rz-dmac.c
@@ -10,6 +10,7 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/cleanup.h>
 #include <linux/dma-mapping.h>
 #include <linux/dmaengine.h>
 #include <linux/interrupt.h>
@@ -448,6 +449,7 @@ static int rz_dmac_alloc_chan_resources(struct dma_chan *chan)
 		if (!desc)
 			break;
 
+		/* No need to lock. This is called only for the 1st client. */
 		list_add_tail(&desc->node, &channel->ld_free);
 		channel->descs_allocated++;
 	}
@@ -503,18 +505,21 @@ rz_dmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 	dev_dbg(dmac->dev, "%s channel: %d src=0x%pad dst=0x%pad len=%zu\n",
 		__func__, channel->index, &src, &dest, len);
 
-	if (list_empty(&channel->ld_free))
-		return NULL;
+	scoped_guard(spinlock_irqsave, &channel->vc.lock) {
+		if (list_empty(&channel->ld_free))
+			return NULL;
+
+		desc = list_first_entry(&channel->ld_free, struct rz_dmac_desc, node);
 
-	desc = list_first_entry(&channel->ld_free, struct rz_dmac_desc, node);
+		desc->type = RZ_DMAC_DESC_MEMCPY;
+		desc->src = src;
+		desc->dest = dest;
+		desc->len = len;
+		desc->direction = DMA_MEM_TO_MEM;
 
-	desc->type = RZ_DMAC_DESC_MEMCPY;
-	desc->src = src;
-	desc->dest = dest;
-	desc->len = len;
-	desc->direction = DMA_MEM_TO_MEM;
+		list_move_tail(channel->ld_free.next, &channel->ld_queue);
+	}
 
-	list_move_tail(channel->ld_free.next, &channel->ld_queue);
 	return vchan_tx_prep(&channel->vc, &desc->vd, flags);
 }
 
@@ -530,27 +535,29 @@ rz_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 	int dma_length = 0;
 	int i = 0;
 
-	if (list_empty(&channel->ld_free))
-		return NULL;
+	scoped_guard(spinlock_irqsave, &channel->vc.lock) {
+		if (list_empty(&channel->ld_free))
+			return NULL;
 
-	desc = list_first_entry(&channel->ld_free, struct rz_dmac_desc, node);
+		desc = list_first_entry(&channel->ld_free, struct rz_dmac_desc, node);
 
-	for_each_sg(sgl, sg, sg_len, i) {
-		dma_length += sg_dma_len(sg);
-	}
+		for_each_sg(sgl, sg, sg_len, i)
+			dma_length += sg_dma_len(sg);
 
-	desc->type = RZ_DMAC_DESC_SLAVE_SG;
-	desc->sg = sgl;
-	desc->sgcount = sg_len;
-	desc->len = dma_length;
-	desc->direction = direction;
+		desc->type = RZ_DMAC_DESC_SLAVE_SG;
+		desc->sg = sgl;
+		desc->sgcount = sg_len;
+		desc->len = dma_length;
+		desc->direction = direction;
 
-	if (direction == DMA_DEV_TO_MEM)
-		desc->src = channel->src_per_address;
-	else
-		desc->dest = channel->dst_per_address;
+		if (direction == DMA_DEV_TO_MEM)
+			desc->src = channel->src_per_address;
+		else
+			desc->dest = channel->dst_per_address;
+
+		list_move_tail(channel->ld_free.next, &channel->ld_queue);
+	}
 
-	list_move_tail(channel->ld_free.next, &channel->ld_queue);
 	return vchan_tx_prep(&channel->vc, &desc->vd, flags);
 }
 
-- 
2.43.0