[PATCH 5/5] drm/simpledrm: Synchronize access to GEM BOs

[Thomas Zimmermann]

Synchronize CPU access to GEM BOs with other drivers when updating the
screen buffer. Imported buffers might otherwise contain stale data.

Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de>
---
 drivers/gpu/drm/tiny/simpledrm.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
index 5f242558891e..18489779fb8a 100644
--- a/drivers/gpu/drm/tiny/simpledrm.c
+++ b/drivers/gpu/drm/tiny/simpledrm.c
@@ -480,11 +480,15 @@ static void 
simpledrm_primary_plane_helper_atomic_update(struct drm_plane *plane
        struct simpledrm_device *sdev = simpledrm_device_of_dev(dev);
        struct drm_atomic_helper_damage_iter iter;
        struct drm_rect damage;
-       int idx;
+       int ret, idx;
 
-       if (!drm_dev_enter(dev, &idx))
+       ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
+       if (ret)
                return;
 
+       if (!drm_dev_enter(dev, &idx))
+               goto out_drm_gem_fb_end_cpu_access;
+
        drm_atomic_helper_damage_iter_init(&iter, old_plane_state, plane_state);
        drm_atomic_for_each_plane_damage(&iter, &damage) {
                struct iosys_map dst = IOSYS_MAP_INIT_VADDR(sdev->screen_base);
@@ -499,6 +503,8 @@ static void 
simpledrm_primary_plane_helper_atomic_update(struct drm_plane *plane
        }
 
        drm_dev_exit(idx);
+out_drm_gem_fb_end_cpu_access:
+       drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
 }
 
 static void simpledrm_primary_plane_helper_atomic_disable(struct drm_plane 
*plane,
-- 
2.37.3