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From: Amelie Delaunay <amelie.delaunay@foss.st.com>
To: Vinod Koul <vkoul@kernel.org>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: <dmaengine@vger.kernel.org>,
	<linux-stm32@st-md-mailman.stormreply.com>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>,
	Amelie Delaunay <amelie.delaunay@foss.st.com>,
	Pierre-Yves Mordret <pierre-yves.mordret@foss.st.com>
Subject: [PATCH 3/3] dmaengine: stm32-dma: fix burst in case of unaligned memory address
Date: Mon, 11 Oct 2021 11:42:59 +0200	[thread overview]
Message-ID: <20211011094259.315023-4-amelie.delaunay@foss.st.com> (raw)
In-Reply-To: <20211011094259.315023-1-amelie.delaunay@foss.st.com>

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>
---
 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 6e4ef44941ef..2283c500f4ce 100644
--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -753,8 +753,14 @@ 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,
@@ -803,8 +809,14 @@ 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,
-- 
2.25.1


WARNING: multiple messages have this Message-ID (diff)
From: Amelie Delaunay <amelie.delaunay@foss.st.com>
To: Vinod Koul <vkoul@kernel.org>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: <dmaengine@vger.kernel.org>,
	<linux-stm32@st-md-mailman.stormreply.com>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>,
	Amelie Delaunay <amelie.delaunay@foss.st.com>,
	Pierre-Yves Mordret <pierre-yves.mordret@foss.st.com>
Subject: [PATCH 3/3] dmaengine: stm32-dma: fix burst in case of unaligned memory address
Date: Mon, 11 Oct 2021 11:42:59 +0200	[thread overview]
Message-ID: <20211011094259.315023-4-amelie.delaunay@foss.st.com> (raw)
In-Reply-To: <20211011094259.315023-1-amelie.delaunay@foss.st.com>

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>
---
 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 6e4ef44941ef..2283c500f4ce 100644
--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -753,8 +753,14 @@ 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,
@@ -803,8 +809,14 @@ 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,
-- 
2.25.1


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  parent reply	other threads:[~2021-10-11  9:43 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-11  9:42 [PATCH 0/3] dmaengine: stm32-dma: some corner case fixes Amelie Delaunay
2021-10-11  9:42 ` Amelie Delaunay
2021-10-11  9:42 ` [PATCH 1/3] dmaengine: stm32-dma: mark pending descriptor complete in terminate_all Amelie Delaunay
2021-10-11  9:42   ` Amelie Delaunay
2021-10-11  9:42 ` [PATCH 2/3] dmaengine: stm32-dma: fix stm32_dma_get_max_width Amelie Delaunay
2021-10-11  9:42   ` Amelie Delaunay
2021-10-11  9:42 ` Amelie Delaunay [this message]
2021-10-11  9:42   ` [PATCH 3/3] dmaengine: stm32-dma: fix burst in case of unaligned memory address Amelie Delaunay
2021-10-18  6:43 ` [PATCH 0/3] dmaengine: stm32-dma: some corner case fixes Vinod Koul
2021-10-18  6:43   ` Vinod Koul

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