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[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: commit1159898a88("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>
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. 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