[PATCH 0/4] drm/msm/dp: ST_DISPLAY_OFF hpd cleanup

[Jessica Zhang <jessica.zhang@oss.qualcomm.com>]

HPD state machine in msm dp display driver manages the state transitions
between various HPD events and the expected state of driver to make sure
both match up.

Although originally done with the intent of managing userspace interactions
and interactions with compliance equipment, over period of time,
changes to this piece of code has become quite difficult to manage.

Although, unwinding this logic will take some time and will be spread over
various changes, to start things, this series tries to get rid of the
ST_DISPLAY_OFF state as firstly, its really not an hpd state but a state
of the display overall. Coupled with this, there are quite a few checks
in the current code, the origins of which need to be re-visited OR are unclear
which seem unlikely or redundant. With DP controller on newer chipsets supporting
multiple streams, this has become increasingly difficult to work with.

This series removes the redundant state checks and simplifies the logic as an
attempt to get rid of this ST_DISPLAY_OFF state.

Note: This series has been tested with sa8775p and sc7180 devices with multiple
monitors and also multiple dongles with no noticeable regressions.
Both of these devices use native DP PHY though. Hence, if this series can
be verified on some devices with USBC-DP combo PHY with the help of the other
developers, that will be great.

---
Changes in v2:
- Rebased on top of next-20250523
- Change atomic_enable() to return early if ST_DISCONENCT_PENDING
  instead of completely dropping the
  if (state != ST_DISPLAY_OFF && state != ST_MAINLINK_READY) check (Dmitry)

---
Abhinav Kumar (4):
      drm/msm/dp: remove redundant checks related to ST_DISPLAY_OFF in plug/irq_ipd handlers
      drm/msm/dp: Return early from atomic_enable() if ST_DISCONNECT_PENDING
      drm/msm/dp: replace ST_DISPLAY_OFF with power_on in msm_dp_hpd_unplug_handle()
      drm/msm/dp: remove ST_DISPLAY_OFF as a hpd_state

 drivers/gpu/drm/msm/dp/dp_display.c | 19 +++----------------
 1 file changed, 3 insertions(+), 16 deletions(-)
---
base-commit: daf70030586cf0279a57b58a94c32cfe901df23d
change-id: 20241202-hpd_display_off-6051aa510f23

Best regards,
-- 
Jessica Zhang <jessica.zhang@oss.qualcomm.com>