[PATCH v2 1/5] drm/rockchip: fix fb references in async update

Helen Koike
2019-03-12T02:21:59Z

In the case of async update, modifications are done in place, i.e. in the
current plane state, so the new_state is prepared and the new_state is
cleanup up (instead of the old_state, diferrently on what happen in a
normal sync update).
To cleanup the old_fb properly, it needs to be placed in the new_state
in the end of async_update, so cleanup call will unreference the old_fb
correctly.

Also, the previous code had a:

plane_state = plane->funcs->atomic_duplicate_state(plane);
...
swap(plane_state, plane->state);

if (plane->state->fb && plane->state->fb != new_state->fb) {
...
}

Which was wrong, as the fb were just assigned to be equal, so this if
statement nevers evaluates to true.

Another details is that the function drm_crtc_vblank_get() can only be
called when vop->is_enabled is true, otherwise it has no effect and
trows a WARN_ON().

Calling drm_atomic_set_fb_for_plane() (which get a referent of the new
fb and pus the old fb) is not required, as it is taken care by
drm_mode_cursor_universal() when calling
drm_atomic_helper_update_plane().

Signed-off-by: Helen Koike <helen.koike@collabora.com>

---
Hello,

I tested on the rockchip ficus v1.1 using igt plane_cursor_legacy and
kms_cursor_legacy and I didn't see any regressions.

Changes in v2: None

drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 42 ++++++++++++---------
1 file changed, 24 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
index c7d4c6073ea5..a1ee8c156a7b 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
@@ -912,30 +912,31 @@ static void vop_plane_atomic_async_update(struct drm_plane *plane,
struct drm_plane_state *new_state)
{
struct vop *vop = to_vop(plane->state->crtc);
- struct drm_plane_state *plane_state;
+ struct drm_framebuffer *old_fb = plane->state->fb;

- plane_state = plane->funcs->atomic_duplicate_state(plane);
- plane_state->crtc_x = new_state->crtc_x;
- plane_state->crtc_y = new_state->crtc_y;
- plane_state->crtc_h = new_state->crtc_h;
- plane_state->crtc_w = new_state->crtc_w;
- plane_state->src_x = new_state->src_x;
- plane_state->src_y = new_state->src_y;
- plane_state->src_h = new_state->src_h;
- plane_state->src_w = new_state->src_w;
-
- if (plane_state->fb != new_state->fb)
- drm_atomic_set_fb_for_plane(plane_state, new_state->fb);
-
- swap(plane_state, plane->state);
-
- if (plane->state->fb && plane->state->fb != new_state->fb) {
+ /*
+ * A scanout can still be occurring, so we can't drop the reference to
+ * the old framebuffer. To solve this we get a reference to old_fb and
+ * set a worker to release it later.
+ */
+ if (vop->is_enabled &&
+ plane->state->fb && plane->state->fb != new_state->fb) {
drm_framebuffer_get(plane->state->fb);
WARN_ON(drm_crtc_vblank_get(plane->state->crtc) != 0);
drm_flip_work_queue(&vop->fb_unref_work, plane->state->fb);
set_bit(VOP_PENDING_FB_UNREF, &vop->pending);
}

+ plane->state->crtc_x = new_state->crtc_x;
+ plane->state->crtc_y = new_state->crtc_y;
+ plane->state->crtc_h = new_state->crtc_h;
+ plane->state->crtc_w = new_state->crtc_w;
+ plane->state->src_x = new_state->src_x;
+ plane->state->src_y = new_state->src_y;
+ plane->state->src_h = new_state->src_h;
+ plane->state->src_w = new_state->src_w;
+ plane->state->fb = new_state->fb;
+
if (vop->is_enabled) {
rockchip_drm_psr_inhibit_get_state(new_state->state);
vop_plane_atomic_update(plane, plane->state);
@@ -945,7 +946,12 @@ static void vop_plane_atomic_async_update(struct drm_plane *plane,
rockchip_drm_psr_inhibit_put_state(new_state->state);
}

- plane->funcs->atomic_destroy_state(plane, plane_state);
+ /*
+ * In async update we perform inplace modifications and release the
+ * new_state. The following is required so we release the reference of
+ * the old framebuffer.
+ */
+ new_state->fb = old_fb;
}

static const struct drm_plane_helper_funcs plane_helper_funcs = {
--
2.20.1