From 7b814900b8ccb4e61ebe704d42a12dc2d06b4a3a Mon Sep 17 00:00:00 2001 From: Marek Szyprowski Date: Fri, 19 Jun 2020 12:36:17 +0200 Subject: [PATCH] drm: radeon: fix common struct sg_table related issues MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Christian König Link: https://patchwork.freedesktop.org/patch/371172/ Signed-off-by: Christian König --- drivers/gpu/drm/radeon/radeon_ttm.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c index 357e8e98cca9..f4f1e63731a5 100644 --- a/drivers/gpu/drm/radeon/radeon_ttm.c +++ b/drivers/gpu/drm/radeon/radeon_ttm.c @@ -479,7 +479,7 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm) { struct radeon_device *rdev = radeon_get_rdev(ttm->bdev); struct radeon_ttm_tt *gtt = (void *)ttm; - unsigned pinned = 0, nents; + unsigned pinned = 0; int r; int write = !(gtt->userflags & RADEON_GEM_USERPTR_READONLY); @@ -519,9 +519,8 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm) if (r) goto release_sg; - r = -ENOMEM; - nents = dma_map_sg(rdev->dev, ttm->sg->sgl, ttm->sg->nents, direction); - if (nents == 0) + r = dma_map_sgtable(rdev->dev, ttm->sg, direction, 0); + if (r) goto release_sg; drm_prime_sg_to_page_addr_arrays(ttm->sg, ttm->pages, @@ -552,9 +551,9 @@ static void radeon_ttm_tt_unpin_userptr(struct ttm_tt *ttm) return; /* free the sg table and pages again */ - dma_unmap_sg(rdev->dev, ttm->sg->sgl, ttm->sg->nents, direction); + dma_unmap_sgtable(rdev->dev, ttm->sg, direction, 0); - for_each_sg_page(ttm->sg->sgl, &sg_iter, ttm->sg->nents, 0) { + for_each_sgtable_page(ttm->sg, &sg_iter, 0) { struct page *page = sg_page_iter_page(&sg_iter); if (!(gtt->userflags & RADEON_GEM_USERPTR_READONLY)) set_page_dirty(page);