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 the 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. A common mistake was to ignore a result
of the dma_map_sg function and don't use the sg_table->orig_nents at all.
To avoid such issues, lets use common dma-mapping wrappers operating
directly on the struct sg_table objects and adjust references to the
nents and orig_nents respectively.
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
For more information, see '[PATCH v3 00/25] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/5/187
---
drivers/gpu/drm/lima/lima_gem.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
index 5404e0d..fca359d 100644
--- a/drivers/gpu/drm/lima/lima_gem.c
+++ b/drivers/gpu/drm/lima/lima_gem.c
@@ -69,8 +69,7 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
return ret;
if (bo->base.sgt) {
- dma_unmap_sg(dev, bo->base.sgt->sgl,
- bo->base.sgt->nents, DMA_BIDIRECTIONAL);
+ dma_unmap_sgtable(dev, bo->base.sgt, DMA_BIDIRECTIONAL);
sg_free_table(bo->base.sgt);
} else {
bo->base.sgt = kmalloc(sizeof(*bo->base.sgt), GFP_KERNEL);
@@ -80,7 +79,13 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
}
}
- dma_map_sg(dev, sgt.sgl, sgt.nents, DMA_BIDIRECTIONAL);
+ ret = dma_map_sgtable(dev, &sgt, DMA_BIDIRECTIONAL);
+ if (ret) {
+ sg_free_table(&sgt);
+ kfree(bo->base.sgt);
+ bo->base.sgt = NULL;
+ return ret;
+ }
*bo->base.sgt = sgt;
--
1.9.1
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