From a04251fc94b58ec25476e57986dfec727b812c22 Mon Sep 17 00:00:00 2001 From: Thierry Reding Date: Tue, 16 Dec 2014 16:35:26 +0100 Subject: [PATCH] drm/tegra: gem: Flush buffer objects upon allocation Buffers obtained via shmem may still have associated cachelines. If they aren't properly flushed they may cause framebuffer corruption if the cache gets flushed after the application has drawn to it. Signed-off-by: Thierry Reding --- drivers/gpu/drm/tegra/gem.c | 36 ++++++++++++++++++++++++++++++++---- 1 file changed, 32 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c index da32086cbeaf..c888bed4036f 100644 --- a/drivers/gpu/drm/tegra/gem.c +++ b/drivers/gpu/drm/tegra/gem.c @@ -219,19 +219,47 @@ static void tegra_bo_free(struct drm_device *drm, struct tegra_bo *bo) static int tegra_bo_get_pages(struct drm_device *drm, struct tegra_bo *bo, size_t size) { + struct scatterlist *s; + struct sg_table *sgt; + unsigned int i; + bo->pages = drm_gem_get_pages(&bo->gem); if (IS_ERR(bo->pages)) return PTR_ERR(bo->pages); bo->num_pages = size >> PAGE_SHIFT; - bo->sgt = drm_prime_pages_to_sg(bo->pages, bo->num_pages); - if (IS_ERR(bo->sgt)) { - drm_gem_put_pages(&bo->gem, bo->pages, false, false); - return PTR_ERR(bo->sgt); + sgt = drm_prime_pages_to_sg(bo->pages, bo->num_pages); + if (IS_ERR(sgt)) + goto put_pages; + + /* + * Fake up the SG table so that dma_map_sg() can be used to flush the + * pages associated with it. Note that this relies on the fact that + * the DMA API doesn't hook into IOMMU on Tegra, therefore mapping is + * only cache maintenance. + * + * TODO: Replace this by drm_clflash_sg() once it can be implemented + * without relying on symbols that are not exported. + */ + for_each_sg(sgt->sgl, s, sgt->nents, i) + sg_dma_address(s) = sg_phys(s); + + if (dma_map_sg(drm->dev, sgt->sgl, sgt->nents, DMA_TO_DEVICE) == 0) { + sgt = ERR_PTR(-ENOMEM); + goto release_sgt; } + bo->sgt = sgt; + return 0; + +release_sgt: + sg_free_table(sgt); + kfree(sgt); +put_pages: + drm_gem_put_pages(&bo->gem, bo->pages, false, false); + return PTR_ERR(sgt); } static int tegra_bo_alloc(struct drm_device *drm, struct tegra_bo *bo,