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@samsung.com --- 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/media/platform/vsp1/vsp1_drm.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/media/platform/vsp1/vsp1_drm.c b/drivers/media/platform/vsp1/vsp1_drm.c index a4a45d6..8a2624b 100644 --- a/drivers/media/platform/vsp1/vsp1_drm.c +++ b/drivers/media/platform/vsp1/vsp1_drm.c @@ -912,8 +912,9 @@ int vsp1_du_map_sg(struct device *dev, struct sg_table *sgt) * skip cache sync. This will need to be revisited when support for * non-coherent buffers will be added to the DU driver. */ - return dma_map_sg_attrs(vsp1->bus_master, sgt->sgl, sgt->nents, - DMA_TO_DEVICE, DMA_ATTR_SKIP_CPU_SYNC); + return dma_map_sgtable_attrs(vsp1->bus_master, sgt, DMA_TO_DEVICE, + DMA_ATTR_SKIP_CPU_SYNC); + return sgt->nents; } EXPORT_SYMBOL_GPL(vsp1_du_map_sg);
@@ -921,8 +922,8 @@ void vsp1_du_unmap_sg(struct device *dev, struct sg_table *sgt) { struct vsp1_device *vsp1 = dev_get_drvdata(dev);
- dma_unmap_sg_attrs(vsp1->bus_master, sgt->sgl, sgt->nents, - DMA_TO_DEVICE, DMA_ATTR_SKIP_CPU_SYNC); + dma_unmap_sgtable_attrs(vsp1->bus_master, sgt, DMA_TO_DEVICE, + DMA_ATTR_SKIP_CPU_SYNC); } EXPORT_SYMBOL_GPL(vsp1_du_unmap_sg);