[PATCH v5 00/10] drm/msm/dp: Drop the HPD state machine

[Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>]

Currently, all HPD interrupt handling must go through the HPD state
machine.

This has caused many issues where the DRM framework assumes that DP is
in one state while the state machine is stuck in another state.

As discussed here [1], this series:

- Removes the state machine
- Moves link training to atomic_enable()
- Changes the detect() behavior to return true if a display is physically
  plugged in (as opposed to if the DP link is ready).
- Remove event queue and move internal HPD handling to hpd_notify()

To correctly detect the displays which are plugged on boot on the boards
which use dp-connector devices, this series depends on [2]. USB-C and
eDP panels are handled natively.

[1] https://patchwork.freedesktop.org/patch/656312/?series=142010&rev=2#comment_1201738
[2] https://lore.kernel.org/all/20260314-dp-connector-hpd-v1-0-786044cedc17@oss.qualcomm.com/

---
Changes in v5:
- Fixed the EDID clearing on display unplug
- Fixed the initial HPD issue via the external series
- Tested on eDP devices
- Link to v4: https://lore.kernel.org/r/20260305-hpd-refactor-v4-0-39c9d1fef321@oss.qualcomm.com

Changes in v4:
- Fixed PM runtime handling
- Fixed several cases where the HPD machine would loose its state
- Fixed the case where detection was ignoring the plugging in display.
- Link to v3: https://lore.kernel.org/r/20260115-hpd-refactor-v3-0-08e2f3bcd2e0@oss.qualcomm.com

Changes in v3:
- Take over the series (thanks, Jessica, for the previous work!)
- Major rework of the series, squashed the set of patches touching the
  HPD states and handling, it is easier to do it this way rather than
  pulling the strings one by one.
- Link to v2: https://lore.kernel.org/r/20250808-hpd-refactor-v2-0-7f4e1e741aa3@oss.qualcomm.com

Changes in v2:
- Dropped event queue (Dmitry)
- Moved internal HPD handling to use hpd_notify() (Dmitry)
- Reworked bridge detect() to read DPCP and sink count (Dmitry)
- Moved setting of link_trained to plug/unplugged handling
- Dropped msm_dp::connected (Dmitry)
- Squashed all hpd state related patches (Dmitry)
- Link to v1: https://lore.kernel.org/r/20250711-hpd-refactor-v1-0-33cbac823f34@oss.qualcomm.com

---
Dmitry Baryshkov (3):
      drm/msm/dp: drop event data
      drm/msm/dp: turn link_ready into plugged
      drm/msm/dp: clear EDID on display unplug

Jessica Zhang (7):
      drm/msm/dp: fix HPD state status bit shift value
      drm/msm/dp: Fix the ISR_* enum values
      drm/msm/dp: Read DPCD and sink count in bridge detect()
      drm/msm/dp: Move link training to atomic_enable()
      drm/msm/dp: Drop EV_USER_NOTIFICATION
      drm/msm/dp: rework HPD handling
      drm/msm/dp: Add sink_count to debug logs

 drivers/gpu/drm/msm/dp/dp_ctrl.c    |  22 --
 drivers/gpu/drm/msm/dp/dp_ctrl.h    |   1 -
 drivers/gpu/drm/msm/dp/dp_display.c | 714 ++++++++++++------------------------
 drivers/gpu/drm/msm/dp/dp_display.h |   3 +-
 drivers/gpu/drm/msm/dp/dp_drm.c     |  63 +---
 drivers/gpu/drm/msm/dp/dp_drm.h     |   2 +
 drivers/gpu/drm/msm/dp/dp_panel.c   |   8 +
 drivers/gpu/drm/msm/dp/dp_panel.h   |   2 +
 drivers/gpu/drm/msm/dp/dp_reg.h     |   4 +-
 9 files changed, 249 insertions(+), 570 deletions(-)
---
base-commit: 5c9e55fecf9365890c64f14761a80f9413a3b1d1
change-id: 20250523-hpd-refactor-74e25b55620a
prerequisite-change-id: 20260314-dp-connector-hpd-f069e66bc6af:v1
prerequisite-patch-id: 90db75e3fb8bc9c81c67547db7bbd4eefd5d6c40
prerequisite-patch-id: 1c4d030b93a8cc6c98b3447a8685da24eb1f24d5

Best regards,
-- 
With best wishes
Dmitry