From b3ce1fc8100afb5f859f35f9566fba3047fa57e0 Mon Sep 17 00:00:00 2001
From: Amelie Delaunay <amelie.delaunay@foss.st.com>
Date: Mon, 11 Oct 2021 11:42:59 +0200
Subject: [PATCH] dmaengine: stm32-dma: fix burst in case of unaligned memory address
Git-commit: af229d2c2557b5cf2a3b1eb39847ec1de7446873
Patch-mainline: v5.16-rc1
References: stable-5.14.19

[ Upstream commit af229d2c2557b5cf2a3b1eb39847ec1de7446873 ]

Theorically, address pointers used by STM32 DMA must be chosen so as to
ensure that all transfers within a burst block are aligned on the address
boundary equal to the size of the transfer.
If this is always the case for peripheral addresses on STM32, it is not for
memory addresses if the user doesn't respect this alignment constraint.
To avoid a weird behavior of the DMA controller in this case (no error
triggered but data are not transferred as expected), force no burst.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20211011094259.315023-4-amelie.delaunay@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/dma/stm32-dma.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c
index a5dab5510e62..1b2063fb3d1d 100644
--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -750,8 +750,14 @@ static int stm32_dma_set_xfer_param(struct stm32_dma_chan *chan,
 		if (src_bus_width < 0)
 			return src_bus_width;
 
-		/* Set memory burst size */
-		src_maxburst = STM32_DMA_MAX_BURST;
+		/*
+		 * Set memory burst size - burst not possible if address is not aligned on
+		 * the address boundary equal to the size of the transfer
+		 */
+		if (buf_addr % buf_len)
+			src_maxburst = 1;
+		else
+			src_maxburst = STM32_DMA_MAX_BURST;
 		src_best_burst = stm32_dma_get_best_burst(buf_len,
 							  src_maxburst,
 							  fifoth,
@@ -800,8 +806,14 @@ static int stm32_dma_set_xfer_param(struct stm32_dma_chan *chan,
 		if (dst_bus_width < 0)
 			return dst_bus_width;
 
-		/* Set memory burst size */
-		dst_maxburst = STM32_DMA_MAX_BURST;
+		/*
+		 * Set memory burst size - burst not possible if address is not aligned on
+		 * the address boundary equal to the size of the transfer
+		 */
+		if (buf_addr % buf_len)
+			dst_maxburst = 1;
+		else
+			dst_maxburst = STM32_DMA_MAX_BURST;
 		dst_best_burst = stm32_dma_get_best_burst(buf_len,
 							  dst_maxburst,
 							  fifoth,
-- 
2.26.2