[PATCH v3 1/5] drm/rockchip: fix fb references in async update

Helen Koike
2019-03-14T00:20:22Z

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
cleaned up (instead of the old_state, unlike what happens 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 v3:
- use swap() to swap old and new framebuffers in async_update
- get the reference to old_fb and set the worker after vop_plane_atomic_update()
- add a FIXME tag for when we have multiple fbs to be released when
vblank happens.
- update commit message

Changes in v2: None

drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 51 +++++++++++----------
1 file changed, 26 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
index c7d4c6073ea5..08f5dcd738a7 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
@@ -912,29 +912,17 @@ 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;
-
- 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) {
- 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);
- }
+ struct drm_framebuffer *old_fb = plane->state->fb;
+
+ 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;
+ swap(plane->state->fb, new_state->fb);

if (vop->is_enabled) {
rockchip_drm_psr_inhibit_get_state(new_state->state);
@@ -943,9 +931,22 @@ static void vop_plane_atomic_async_update(struct drm_plane *plane,
vop_cfg_done(vop);
spin_unlock(&vop->reg_lock);
rockchip_drm_psr_inhibit_put_state(new_state->state);
- }

- plane->funcs->atomic_destroy_state(plane, plane_state);
+ /*
+ * 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.
+ * FIXME: if we perform 500 async_update calls before the
+ * vblank, then we can have 500 different framebuffers waiting
+ * to be released.
+ */
+ if (old_fb && plane->state->fb != old_fb) {
+ drm_framebuffer_get(old_fb);
+ WARN_ON(drm_crtc_vblank_get(plane->state->crtc) != 0);
+ drm_flip_work_queue(&vop->fb_unref_work, old_fb);
+ set_bit(VOP_PENDING_FB_UNREF, &vop->pending);
+ }
+ }
}

static const struct drm_plane_helper_funcs plane_helper_funcs = {
--
2.20.1

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