drm/client: Depend on GEM object kmap ref-counting

DRM client's vmap/vunmap functions don't allow for multiple vmap
operations. Calling drm_client_buffer_vmap() twice returns the same
mapping, then calling drm_client_buffer_vunmap() twice already unmaps
on the first call. This leads to unbalanced vmap refcounts. Fix this
by calling drm_gem_vmap() unconditionally in drm_client_buffer_vmap().

All drivers that support DRM clients have to implement correct ref-
counting for their vmap operations, or not vunmap at all. This is the
case for drivers that use CMA, SHMEM and VRAM helpers, and QXL. Other
drivers are not affected.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201120102545.4047-4-tzimmermann@suse.de

diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
index fe573acf106715baa23ab0f7ce2829e9334a7f89..ce45e380f4a2028fe3f64909a80de2d92d94bcf7 100644 (file)
--- a/drivers/gpu/drm/drm_client.c
+++ b/drivers/gpu/drm/drm_client.c
@@ -314,9 +314,6 @@ drm_client_buffer_vmap(struct drm_client_buffer *buffer, struct dma_buf_map *map
        struct dma_buf_map *map = &buffer->map;
        int ret;
 
-       if (dma_buf_map_is_set(map))
-               goto out;
-
        /*
         * FIXME: The dependency on GEM here isn't required, we could
         * convert the driver handle to a dma-buf instead and use the
@@ -329,7 +326,6 @@ drm_client_buffer_vmap(struct drm_client_buffer *buffer, struct dma_buf_map *map
        if (ret)
                return ret;
 
-out:
        *map_copy = *map;
 
        return 0;