drm/tegra: gem: Fix CPU-cache maintenance for BO's allocated using get_pages()

The allocated pages need to be invalidated in CPU caches. On ARM32 the
DMA_BIDIRECTIONAL flag only ensures that data is written-back to DRAM and
the data stays in CPU cache lines. While the DMA_FROM_DEVICE flag ensures
that the corresponding CPU cache lines are getting invalidated and nothing
more, that's exactly what is needed for a newly allocated pages.

This fixes randomly failing rendercheck tests on Tegra30 using the
Opentegra driver for tests that use small-sized pixmaps (10x10 and less,
i.e. 1-2 memory pages) because apparently CPU reads out stale data from
caches and/or that data is getting evicted to DRAM at the time of HW job
execution.

Fixes: bd43c9f0fa1f ("drm/tegra: gem: Map pages via the DMA API")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
index 4f80100ff5f34b7ca997fb5a31a8c3c6788e59cf..4cce11fd8836f93ec76cc43a0a535a9764617a09 100644 (file)
--- a/drivers/gpu/drm/tegra/gem.c
+++ b/drivers/gpu/drm/tegra/gem.c
@@ -204,7 +204,7 @@ static void tegra_bo_free(struct drm_device *drm, struct tegra_bo *bo)
 {
        if (bo->pages) {
                dma_unmap_sg(drm->dev, bo->sgt->sgl, bo->sgt->nents,
-                            DMA_BIDIRECTIONAL);
+                            DMA_FROM_DEVICE);
                drm_gem_put_pages(&bo->gem, bo->pages, true, true);
                sg_free_table(bo->sgt);
                kfree(bo->sgt);
@@ -230,7 +230,7 @@ static int tegra_bo_get_pages(struct drm_device *drm, struct tegra_bo *bo)
        }
 
        err = dma_map_sg(drm->dev, bo->sgt->sgl, bo->sgt->nents,
-                        DMA_BIDIRECTIONAL);
+                        DMA_FROM_DEVICE);
        if (err == 0) {
                err = -EFAULT;
                goto free_sgt;