On 6/29/22 01:42, Dmitry Osipenko wrote:
> The code assumes that Tegra GEM is permanently vmapped, which is not
> true for the scattered buffers. After converting Tegra video decoder
> driver to V4L API, we're now getting a BUG_ON from dma-buf core on playing
> video using libvdpau-tegra on T30+ because tegra_gem_prime_vmap() sets
> vaddr to NULL. Older pre-V4L video decoder driver wasn't vmapping dma-bufs.
> Fix it by actually vmapping the exported GEMs.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/tegra/gem.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
> index 7c7dd84e6db8..81991090adcc 100644
> --- a/drivers/gpu/drm/tegra/gem.c
> +++ b/drivers/gpu/drm/tegra/gem.c
> @@ -704,14 +704,23 @@ static int tegra_gem_prime_vmap(struct dma_buf *buf, struct iosys_map *map)
> {
> struct drm_gem_object *gem = buf->priv;
> struct tegra_bo *bo = to_tegra_bo(gem);
> + void *vaddr;
>
> - iosys_map_set_vaddr(map, bo->vaddr);
> + vaddr = tegra_bo_mmap(&bo->base);
> + if (IS_ERR(vaddr))
> + return PTR_ERR(vaddr);
> +
> + iosys_map_set_vaddr(map, vaddr);
>
> return 0;
> }
>
> static void tegra_gem_prime_vunmap(struct dma_buf *buf, struct iosys_map *map)
> {
> + struct drm_gem_object *gem = buf->priv;
> + struct tegra_bo *bo = to_tegra_bo(gem);
> +
> + tegra_bo_munmap(&bo->base, map->vaddr);
> }
>
> static const struct dma_buf_ops tegra_gem_prime_dmabuf_ops = {
BTW, previously I only tested video dec on T30 using the grate-driver
kernel that properly vmaps GEMs. That's why it wasn't caught earlier.
--
Best regards,
Dmitry
