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[RFC,07/17] drm: lima: fix sg_table nents vs. orig_nents misuse

Message ID 20200428132005.21424-8-m.szyprowski@samsung.com (mailing list archive)
State New, archived
Headers show
Series DRM: fix struct sg_table nents vs. orig_nents misuse | expand

Commit Message

Marek Szyprowski April 28, 2020, 1:19 p.m. UTC 
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>
---
 drivers/gpu/drm/lima/lima_gem.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
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Patch

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;