| Message ID | 20200826063316.23486-18-m.szyprowski@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | None | expand |
On 2020-08-26 07:33, Marek Szyprowski wrote: > The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function > returns the number of the created entries in the DMA address space. > However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and > dma_unmap_sg must be called with the original number of the entries > passed to the dma_map_sg(). > > struct sg_table is a common structure used for describing a non-contiguous > memory buffer, used commonly in the DRM and graphics subsystems. It > consists of a scatterlist with memory pages and DMA addresses (sgl entry), > as well as the number of scatterlist entries: CPU pages (orig_nents entry) > and DMA mapped pages (nents entry). > > It turned out that it was a common mistake to misuse nents and orig_nents > entries, calling DMA-mapping functions with a wrong number of entries or > ignoring the number of mapped entries returned by the dma_map_sg() > function. > > To avoid such issues, lets use a common dma-mapping wrappers operating > directly on the struct sg_table objects and use scatterlist page > iterators where possible. This, almost always, hides references to the > nents and orig_nents entries, making the code robust, easier to follow > and copy/paste safe. Reviewed-by: Robin Murphy <robin.murphy@arm.com> (Until now I hadn't noticed the crimes against the API that rockchip_gem_get_pages() is committing, but it's not this patch's fault... I'll have to take a closer look at that) > Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> > --- > drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 23 +++++++++------------ > 1 file changed, 10 insertions(+), 13 deletions(-) > > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c > index 2970e534e2bb..cb50f2ba2e46 100644 > --- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c > +++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c > @@ -36,8 +36,8 @@ static int rockchip_gem_iommu_map(struct rockchip_gem_object *rk_obj) > > rk_obj->dma_addr = rk_obj->mm.start; > > - ret = iommu_map_sg(private->domain, rk_obj->dma_addr, rk_obj->sgt->sgl, > - rk_obj->sgt->nents, prot); > + ret = iommu_map_sgtable(private->domain, rk_obj->dma_addr, rk_obj->sgt, > + prot); > if (ret < rk_obj->base.size) { > DRM_ERROR("failed to map buffer: size=%zd request_size=%zd\n", > ret, rk_obj->base.size); > @@ -98,11 +98,10 @@ static int rockchip_gem_get_pages(struct rockchip_gem_object *rk_obj) > * TODO: Replace this by drm_clflush_sg() once it can be implemented > * without relying on symbols that are not exported. > */ > - for_each_sg(rk_obj->sgt->sgl, s, rk_obj->sgt->nents, i) > + for_each_sgtable_sg(rk_obj->sgt, s, i) > sg_dma_address(s) = sg_phys(s); > > - dma_sync_sg_for_device(drm->dev, rk_obj->sgt->sgl, rk_obj->sgt->nents, > - DMA_TO_DEVICE); > + dma_sync_sgtable_for_device(drm->dev, rk_obj->sgt, DMA_TO_DEVICE); > > return 0; > > @@ -350,8 +349,8 @@ void rockchip_gem_free_object(struct drm_gem_object *obj) > if (private->domain) { > rockchip_gem_iommu_unmap(rk_obj); > } else { > - dma_unmap_sg(drm->dev, rk_obj->sgt->sgl, > - rk_obj->sgt->nents, DMA_BIDIRECTIONAL); > + dma_unmap_sgtable(drm->dev, rk_obj->sgt, > + DMA_BIDIRECTIONAL, 0); > } > drm_prime_gem_destroy(obj, rk_obj->sgt); > } else { > @@ -476,15 +475,13 @@ rockchip_gem_dma_map_sg(struct drm_device *drm, > struct sg_table *sg, > struct rockchip_gem_object *rk_obj) > { > - int count = dma_map_sg(drm->dev, sg->sgl, sg->nents, > - DMA_BIDIRECTIONAL); > - if (!count) > - return -EINVAL; > + int err = dma_map_sgtable(drm->dev, sg, DMA_BIDIRECTIONAL, 0); > + if (err) > + return err; > > if (drm_prime_get_contiguous_size(sg) < attach->dmabuf->size) { > DRM_ERROR("failed to map sg_table to contiguous linear address.\n"); > - dma_unmap_sg(drm->dev, sg->sgl, sg->nents, > - DMA_BIDIRECTIONAL); > + dma_unmap_sgtable(drm->dev, sg, DMA_BIDIRECTIONAL, 0); > return -EINVAL; > } > >
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c index 2970e534e2bb..cb50f2ba2e46 100644 --- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c +++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c @@ -36,8 +36,8 @@ static int rockchip_gem_iommu_map(struct rockchip_gem_object *rk_obj) rk_obj->dma_addr = rk_obj->mm.start; - ret = iommu_map_sg(private->domain, rk_obj->dma_addr, rk_obj->sgt->sgl, - rk_obj->sgt->nents, prot); + ret = iommu_map_sgtable(private->domain, rk_obj->dma_addr, rk_obj->sgt, + prot); if (ret < rk_obj->base.size) { DRM_ERROR("failed to map buffer: size=%zd request_size=%zd\n", ret, rk_obj->base.size); @@ -98,11 +98,10 @@ static int rockchip_gem_get_pages(struct rockchip_gem_object *rk_obj) * TODO: Replace this by drm_clflush_sg() once it can be implemented * without relying on symbols that are not exported. */ - for_each_sg(rk_obj->sgt->sgl, s, rk_obj->sgt->nents, i) + for_each_sgtable_sg(rk_obj->sgt, s, i) sg_dma_address(s) = sg_phys(s); - dma_sync_sg_for_device(drm->dev, rk_obj->sgt->sgl, rk_obj->sgt->nents, - DMA_TO_DEVICE); + dma_sync_sgtable_for_device(drm->dev, rk_obj->sgt, DMA_TO_DEVICE); return 0; @@ -350,8 +349,8 @@ void rockchip_gem_free_object(struct drm_gem_object *obj) if (private->domain) { rockchip_gem_iommu_unmap(rk_obj); } else { - dma_unmap_sg(drm->dev, rk_obj->sgt->sgl, - rk_obj->sgt->nents, DMA_BIDIRECTIONAL); + dma_unmap_sgtable(drm->dev, rk_obj->sgt, + DMA_BIDIRECTIONAL, 0); } drm_prime_gem_destroy(obj, rk_obj->sgt); } else { @@ -476,15 +475,13 @@ rockchip_gem_dma_map_sg(struct drm_device *drm, struct sg_table *sg, struct rockchip_gem_object *rk_obj) { - int count = dma_map_sg(drm->dev, sg->sgl, sg->nents, - DMA_BIDIRECTIONAL); - if (!count) - return -EINVAL; + int err = dma_map_sgtable(drm->dev, sg, DMA_BIDIRECTIONAL, 0); + if (err) + return err; if (drm_prime_get_contiguous_size(sg) < attach->dmabuf->size) { DRM_ERROR("failed to map sg_table to contiguous linear address.\n"); - dma_unmap_sg(drm->dev, sg->sgl, sg->nents, - DMA_BIDIRECTIONAL); + dma_unmap_sgtable(drm->dev, sg, DMA_BIDIRECTIONAL, 0); return -EINVAL; }
The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function returns the number of the created entries in the DMA address space. However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and dma_unmap_sg must be called with the original number of the entries passed to the dma_map_sg(). struct sg_table is a common structure used for describing a non-contiguous memory buffer, used commonly in the DRM and graphics subsystems. It consists of a scatterlist with memory pages and DMA addresses (sgl entry), as well as the number of scatterlist entries: CPU pages (orig_nents entry) and DMA mapped pages (nents entry). It turned out that it was a common mistake to misuse nents and orig_nents entries, calling DMA-mapping functions with a wrong number of entries or ignoring the number of mapped entries returned by the dma_map_sg() function. To avoid such issues, lets use a common dma-mapping wrappers operating directly on the struct sg_table objects and use scatterlist page iterators where possible. This, almost always, hides references to the nents and orig_nents entries, making the code robust, easier to follow and copy/paste safe. Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> --- drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 23 +++++++++------------ 1 file changed, 10 insertions(+), 13 deletions(-)