linux-kernel - [PATCH 6/9] dmaengine: dw-edma: HDMA: Fix possible race condition in local setup

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Message-Id: <20230609081654.330857-7-kory.maincent@bootlin.com>
Date:   Fri,  9 Jun 2023 10:16:51 +0200
From:   Köry Maincent <kory.maincent@...tlin.com>
To:     Cai Huoqing <cai.huoqing@...ux.dev>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Serge Semin <fancer.lancer@...il.com>,
        Vinod Koul <vkoul@...nel.org>,
        Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Herve Codina <herve.codina@...tlin.com>,
        Kory Maincent <kory.maincent@...tlin.com>
Subject: [PATCH 6/9] dmaengine: dw-edma: HDMA: Fix possible race condition in local setup

From: Kory Maincent <kory.maincent@...tlin.com>

When writing the linked list elements and pointer the control need to be
written at the end. If the control is written and the SAR and DAR not
stored we could face a race condition. Added a memory barrier to make sure
the memory has been written.

Fixes: e74c39573d35 ("dmaengine: dw-edma: Add support for native HDMA")
Signed-off-by: Kory Maincent <kory.maincent@...tlin.com>
---

This patch has not been tested since I don't have board with HDMA in local
setup.

This patch is fixing a commit which is only in dmaengine tree and not
merged mainline.
---
 drivers/dma/dw-edma/dw-hdma-v0-core.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c b/drivers/dma/dw-edma/dw-hdma-v0-core.c
index f28e1671a753..d3c70500496c 100644
--- a/drivers/dma/dw-edma/dw-hdma-v0-core.c
+++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c
@@ -155,10 +155,13 @@ static void dw_hdma_v0_write_ll_data(struct dw_edma_chunk *chunk, int i,
 	if (chunk->chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL) {
 		struct dw_hdma_v0_lli *lli = chunk->ll_region.vaddr.mem + ofs;
 
-		lli->control = control;
 		lli->transfer_size = size;
 		lli->sar.reg = sar;
 		lli->dar.reg = dar;
+
+		/* Make sure sar and dar is written before writing control */
+		dma_wmb();
+		lli->control = control;
 	} else {
 		struct dw_hdma_v0_lli __iomem *lli = chunk->ll_region.vaddr.io + ofs;
 
@@ -177,8 +180,11 @@ static void dw_hdma_v0_write_ll_link(struct dw_edma_chunk *chunk,
 	if (chunk->chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL) {
 		struct dw_hdma_v0_llp *llp = chunk->ll_region.vaddr.mem + ofs;
 
-		llp->control = control;
 		llp->llp.reg = pointer;
+
+		/* Make sure sar and dar is written before writing control */
+		dma_wmb();
+		llp->control = control;
 	} else {
 		struct dw_hdma_v0_llp __iomem *llp = chunk->ll_region.vaddr.io + ofs;
 
-- 
2.25.1