drm/tegra: prime: Implement ->{begin,end}_cpu_access()

These callbacks allow the exporter to swap in and pin the backing
storage for buffers as well as invalidate the cache in preparation for
accessing the buffer from the CPU, and flush the cache and unpin the
backing storage when the CPU is done modifying the buffer.
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/gem.c

@@ -568,6 +568,34 @@ static void tegra_gem_prime_release(struct dma_buf *buf)
 	drm_gem_dmabuf_release(buf);
 }
 
+static int tegra_gem_prime_begin_cpu_access(struct dma_buf *buf,
+					    enum dma_data_direction direction)
+{
+	struct drm_gem_object *gem = buf->priv;
+	struct tegra_bo *bo = to_tegra_bo(gem);
+	struct drm_device *drm = gem->dev;
+
+	if (bo->pages)
+		dma_sync_sg_for_cpu(drm->dev, bo->sgt->sgl, bo->sgt->nents,
+				    DMA_FROM_DEVICE);
+
+	return 0;
+}
+
+static int tegra_gem_prime_end_cpu_access(struct dma_buf *buf,
+					  enum dma_data_direction direction)
+{
+	struct drm_gem_object *gem = buf->priv;
+	struct tegra_bo *bo = to_tegra_bo(gem);
+	struct drm_device *drm = gem->dev;
+
+	if (bo->pages)
+		dma_sync_sg_for_device(drm->dev, bo->sgt->sgl, bo->sgt->nents,
+				       DMA_TO_DEVICE);
+
+	return 0;
+}
+
 static void *tegra_gem_prime_kmap_atomic(struct dma_buf *buf,
 					 unsigned long page)
 {
@@ -618,6 +646,8 @@ static const struct dma_buf_ops tegra_gem_prime_dmabuf_ops = {
 	.map_dma_buf = tegra_gem_prime_map_dma_buf,
 	.unmap_dma_buf = tegra_gem_prime_unmap_dma_buf,
 	.release = tegra_gem_prime_release,
+	.begin_cpu_access = tegra_gem_prime_begin_cpu_access,
+	.end_cpu_access = tegra_gem_prime_end_cpu_access,
 	.map_atomic = tegra_gem_prime_kmap_atomic,
 	.unmap_atomic = tegra_gem_prime_kunmap_atomic,
 	.map = tegra_gem_prime_kmap,