[PATCH 4/4] dmaengine: dw-edma: Add spinlock to protect DONE_INT_MASK and ABORT_INT_MASK

[Koichiro Den]

From: Frank Li <Frank.Li@xxxxxxx>

The DONE_INT_MASK and ABORT_INT_MASK registers are shared by all DMA
channels, and modifying them requires a read-modify-write sequence.
Because this operation is not atomic, concurrent calls to
dw_edma_v0_core_start() can introduce race conditions if two channels
update these registers simultaneously.

Add a spinlock to serialize access to these registers and prevent race
conditions.

Fixes: 7e4b8a4fbe2c ("dmaengine: Add Synopsys eDMA IP version 0 support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
[den: update dw_edma.lock comment]
Link: https://lore.kernel.org/dmaengine/20260109-edma_ll-v2-1-5c0b27b2c664@xxxxxxx/
Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
---
 drivers/dma/dw-edma/dw-edma-core.h    | 2 +-
 drivers/dma/dw-edma/dw-edma-v0-core.c | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/dw-edma/dw-edma-core.h b/drivers/dma/dw-edma/dw-edma-core.h
index 902574b1ba86..6474cacf7195 100644
--- a/drivers/dma/dw-edma/dw-edma-core.h
+++ b/drivers/dma/dw-edma/dw-edma-core.h
@@ -109,7 +109,7 @@ struct dw_edma {
 
 	struct dw_edma_chan		*chan;
 
-	raw_spinlock_t			lock;		/* Only for legacy */
+	raw_spinlock_t			lock;		/* Protect v0 shared registers */
 
 	struct dw_edma_chip             *chip;
 
diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c b/drivers/dma/dw-edma/dw-edma-v0-core.c
index 69e8279adec8..cfdd6463252e 100644
--- a/drivers/dma/dw-edma/dw-edma-v0-core.c
+++ b/drivers/dma/dw-edma/dw-edma-v0-core.c
@@ -364,6 +364,7 @@ static void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
 {
 	struct dw_edma_chan *chan = chunk->chan;
 	struct dw_edma *dw = chan->dw;
+	unsigned long flags;
 	u32 tmp;
 
 	dw_edma_v0_core_write_chunk(chunk);
@@ -408,6 +409,8 @@ static void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
 			}
 		}
 		/* Interrupt unmask - done, abort */
+		raw_spin_lock_irqsave(&dw->lock, flags);
+
 		tmp = GET_RW_32(dw, chan->dir, int_mask);
 		tmp &= ~FIELD_PREP(EDMA_V0_DONE_INT_MASK, BIT(chan->id));
 		tmp &= ~FIELD_PREP(EDMA_V0_ABORT_INT_MASK, BIT(chan->id));
@@ -416,6 +419,9 @@ static void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
 		tmp = GET_RW_32(dw, chan->dir, linked_list_err_en);
 		tmp |= FIELD_PREP(EDMA_V0_LINKED_LIST_ERR_MASK, BIT(chan->id));
 		SET_RW_32(dw, chan->dir, linked_list_err_en, tmp);
+
+		raw_spin_unlock_irqrestore(&dw->lock, flags);
+
 		/* Channel control */
 		SET_CH_32(dw, chan->dir, chan->id, ch_control1,
 			  (DW_EDMA_V0_CCS | DW_EDMA_V0_LLE));
-- 
2.51.0