linux-kernel - [PATCH 1/1] dmaengine: fsl-qdma: fix SoC may hang on 16 byte unaligned read

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Date: Thu,  1 Feb 2024 16:50:07 -0500
From: Frank Li <Frank.Li@....com>
To: Vinod Koul <vkoul@...nel.org>,
	Wen He <wen.he_1@....com>,
	Peng Ma <peng.ma@....com>,
	Jiaheng Fan <jiaheng.fan@....com>,
	dmaengine@...r.kernel.org (open list:DMA GENERIC OFFLOAD ENGINE SUBSYSTEM),
	linux-kernel@...r.kernel.org (open list)
Cc: imx@...ts.linux.dev
Subject: [PATCH 1/1] dmaengine: fsl-qdma: fix SoC may hang on 16 byte unaligned read

From: Peng Ma <peng.ma@....com>

There is chip (ls1028a) errata:

The SoC may hang on 16 byte unaligned read transactions by QDMA.

Unaligned read transactions initiated by QDMA may stall in the NOC
(Network On-Chip), causing a deadlock condition. Stalled transactions will
trigger completion timeouts in PCIe controller.

Workaround:
Enable prefetch by setting the source descriptor prefetchable bit
( SD[PF] = 1 ).

Implement this workaround.

Cc: stable@...r.kernel.org
Fixes: b092529e0aa0 ("dmaengine: fsl-qdma: Add qDMA controller driver for Layerscape SoCs")
Signed-off-by: Peng Ma <peng.ma@....com>
Signed-off-by: Frank Li <Frank.Li@....com>
---
 drivers/dma/fsl-qdma.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/fsl-qdma.c b/drivers/dma/fsl-qdma.c
index 47cb284680494..11d10dcd8b45d 100644
--- a/drivers/dma/fsl-qdma.c
+++ b/drivers/dma/fsl-qdma.c
@@ -109,6 +109,7 @@
 #define FSL_QDMA_CMD_WTHROTL_OFFSET	20
 #define FSL_QDMA_CMD_DSEN_OFFSET	19
 #define FSL_QDMA_CMD_LWC_OFFSET		16
+#define FSL_QDMA_CMD_PF			BIT(17)
 
 /* Field definition for Descriptor status */
 #define QDMA_CCDF_STATUS_RTE		BIT(5)
@@ -384,7 +385,8 @@ static void fsl_qdma_comp_fill_memcpy(struct fsl_qdma_comp *fsl_comp,
 	qdma_csgf_set_f(csgf_dest, len);
 	/* Descriptor Buffer */
 	cmd = cpu_to_le32(FSL_QDMA_CMD_RWTTYPE <<
-			  FSL_QDMA_CMD_RWTTYPE_OFFSET);
+			  FSL_QDMA_CMD_RWTTYPE_OFFSET) |
+			  FSL_QDMA_CMD_PF;
 	sdf->data = QDMA_SDDF_CMD(cmd);
 
 	cmd = cpu_to_le32(FSL_QDMA_CMD_RWTTYPE <<
-- 
2.34.1