drm/amd/display: Exit idle optimizations before programming

drm/amd/display: Exit idle optimizations before programming

[Why]

We need to exit PSR/IPS before programming. Before calling DC for
programming in amdgpu_dm_commit_planes(), there's a
vblank_control_workqueue flush. This waits for IPS and PSR exit. (See
drm_vblank_on/off() > amdgpu_dm_crtc_set_vblank() --queue_work()->
amdgpu_dm_crtc_vblank_control_worker())

Prior to the tagged "Fixes:" change, drm_vblank_get() was called before
the workqueue flush. This ordering ensures that PSR exit occurred before
programming. After the "Fixes:" change, drm_vblank_get() is called after
the workqueue flush, leading to programming while idle optimizations are
still active. This can lead to incorrect flip_pending detection used by
vblank event delivery.

[How]

Split the vblank_get() component of `dm_arm_vblank_event()` into
`dm_arm_vblank_event_pre_programming()`, which is called before
programming. Call it before the vblank_control_workqueue flush.

Includes a drive-by cleanup of prepare_flip_isr(): the only caller is
dm_arm_vblank_event() and it's simple enough to roll-in.

v2: Fix checkpatch formatting warning on
    drm_arm_vblank_event_pre_programming() arg alignment.

Fixes: 48ab86360af1 ("drm/amd/display: check GRPH_FLIP status before sending event")
Cc: stable@vger.kernel.org
Link: https://gitlab.freedesktop.org/drm/amd/-/work_items/4141#note_3583205
Link: https://gitlab.freedesktop.org/drm/amd/-/work_items/5527
Assisted-by: Codex:gpt-5.6-sol
Assisted-by: Claude:opus-5
Suggested-by: David Weber <weber.aulendorf@gmail.com>
Signed-off-by: Leo Li <sunpeng.li@amd.com>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 05984e29520a28c27f5a2388742c957a6a87ee7a)