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From:   Marek Szyprowski <m.szyprowski@samsung.com>
To:     dri-devel@lists.freedesktop.org, iommu@lists.linux-foundation.org,
        linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org
Cc:     Marek Szyprowski <m.szyprowski@samsung.com>,
        Christoph Hellwig <hch@lst.de>,
        Robin Murphy <robin.murphy@arm.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        linux-arm-kernel@lists.infradead.org,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>, Qiang Yu <yuq825@gmail.com>,
        lima@lists.freedesktop.org
Subject: [PATCH v2 07/21] drm: lima: fix sg_table nents vs. orig_nents
 misuse
Date:   Mon,  4 May 2020 14:53:45 +0200
Message-Id: <20200504125359.5678-7-m.szyprowski@samsung.com>
In-Reply-To: <20200504125359.5678-1-m.szyprowski@samsung.com>
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References: <20200504125017.5494-1-m.szyprowski@samsung.com>
        <20200504125359.5678-1-m.szyprowski@samsung.com>
        <CGME20200504125414eucas1p1dc1cbef1c50f430b738e74129babb95b@eucas1p1.samsung.com>
Sender: linux-kernel-owner@vger.kernel.org
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The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the
numer of the created entries in the DMA address space. However the
subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be
called with the original number of entries passed to dma_map_sg. The
sg_table->nents in turn holds the result of the dma_map_sg call as stated
in include/linux/scatterlist.h. Adapt the code to obey those rules.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
For more information, see '[PATCH v2 00/21] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/4/373
---
 drivers/gpu/drm/lima/lima_gem.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
index 5404e0d..3edd2ff 100644
--- a/drivers/gpu/drm/lima/lima_gem.c
+++ b/drivers/gpu/drm/lima/lima_gem.c
@@ -70,7 +70,7 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
 
 	if (bo->base.sgt) {
 		dma_unmap_sg(dev, bo->base.sgt->sgl,
-			     bo->base.sgt->nents, DMA_BIDIRECTIONAL);
+			     bo->base.sgt->orig_nents, DMA_BIDIRECTIONAL);
 		sg_free_table(bo->base.sgt);
 	} else {
 		bo->base.sgt = kmalloc(sizeof(*bo->base.sgt), GFP_KERNEL);
@@ -80,7 +80,7 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
 		}
 	}
 
-	dma_map_sg(dev, sgt.sgl, sgt.nents, DMA_BIDIRECTIONAL);
+	sgt.nents = dma_map_sg(dev, sgt.sgl, sgt.orig_nents, DMA_BIDIRECTIONAL);
 
 	*bo->base.sgt = sgt;
 
-- 
1.9.1