[Why]
After unifying DCN interrupt sources under VUPDATE_NO_LOCK, we have two
remaining issues to clean up:
1. On DCN, flip completion is now delivered from VUPDATE_NO_LOCK
(dm_crtc_high_irq_handler) instead of GRPH_PFLIP. But VUPDATE_NO_LOCK
fires every frame, regardless of whether a flip has latched.
2. There is a window during commit where a flip is armed (pflip_status =
SUBMITTED) but not yet programmed into HW. If the VUPDATE_NO_LOCK
fires in that window, its handler would deliver a flip event to
userspace before HW has latched to it. If userspace then renders to
what it believes is now the back buffer (but HW is still latched to
it!), it will cause display corruption. This issue seemed to have
been introduced by:
commit 1159898a88 ("drm/amd/display: Handle commit plane with no FB.")
Enabling replay or psr extended the duration of this window, and
hence made corruption more likely to be observed.
[How]
* Move acrtc->event/pflip_status arming to after
update_planes_and_stream_adapter() has programmed the flip into HW.
This closes the window where pflip_status is SUBMITTED but the flip is
not yet programmed.
* Add dc_get_flip_pending_on_otg(), which reads the HUBP flip-pending
status straight from HW for the pipe(s) bound to an OTG instance. It
is keyed only by otg_inst and does not take or mutate a
dc_plane_state, so it is safe to call from the OTG interrupt handler
without racing a concurrent commit that may be modifying plane state.
* Optimistically query for flip-pending after programming, in the event
that HW latched to the new fb between programming start and arming
event. If it latched, send the vblank event immediately, rather than
wait for the next vblank IRQ.
* In the VUPDATE_NO_LOCK handler, only deliver flip completion once
dc_get_flip_pending_on_otg() reports the flip is no longer pending.
Otherwise leave the flip armed and retry on the next vupdate.
* For DCE, maintain the existing behavior of arming flips before
programming, and relying on GRPH_FLIP to fire at HW latch.
v2:
* Drop flip_programmed completion object, instead move
event/pflip_status arming after programming.
* For DCN, optimistically query for flip pending immediately after
programming, and if it latched, send event right away.
v3:
* Fix event timestamps on optimistic flip latch detection, where it's
possible for it to run *before* the vupdate IRQ updates the timestamp.
* Add more docstrings for DCN vblank handling.
* Clean up if conditions in dm_arm_vblank_event().
* Code style cleanup on braces surrounding multi-line statements.
Fixes: 9b47278cec ("drm/amd/display: temp w/a for dGPU to enter idle optimizations")
Link: https://gitlab.freedesktop.org/drm/amd/-/work_items/3787
Link: https://gitlab.freedesktop.org/drm/amd/-/work_items/4141
Assisted-by: Copilot:claude-opus-4.8
Tested-by: Mario Limonciello (AMD) <superm1@kernel.org>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit f64a9be565)
Cc: stable@vger.kernel.org # 8382cd234981: drm/amd/display: consolidate DCN vblank/flip handling onto vupdate_no_lock
Cc: stable@vger.kernel.org
48ab86360a