linux-kernel - [PATCH v2 00/12] drm/msm/dp: Drop the HPD state machine

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Message-Id: <20250808-hpd-refactor-v2-0-7f4e1e741aa3@oss.qualcomm.com>
Date: Fri, 08 Aug 2025 17:35:12 -0700
From: Jessica Zhang <jessica.zhang@....qualcomm.com>
To: Rob Clark <robin.clark@....qualcomm.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Dmitry Baryshkov <lumag@...nel.org>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Yongxing Mou <quic_yongmou@...cinc.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>
Subject: [PATCH v2 00/12] drm/msm/dp: Drop the HPD state machine

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()

This has been validated on x1e80100-crd and sa8775p-ride. Any help
testing on other platforms/use-cases would be appreciated!

[1] https://patchwork.freedesktop.org/patch/656312/?series=142010&rev=2#comment_1201738

---
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

---
Abhinav Kumar (1):
      drm/msm/dp: remove redundant checks related to ST_DISPLAY_OFF in plug handler

Jessica Zhang (11):
      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: Use drm_bridge_hpd_notify()
      drm/msm/dp: Handle internal HPD IRQ in hpd_notify()
      drm/msm/dp: Drop event waitqueue
      drm/msm/dp: Return early from atomic_enable() if cable is not connected
      drm/msm/dp: drop the entire HPD state machine
      drm/msm/dp: Add sink_count and link_ready 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 | 580 +++++++++++-------------------------
 drivers/gpu/drm/msm/dp/dp_display.h |   1 +
 drivers/gpu/drm/msm/dp/dp_drm.c     |  20 +-
 drivers/gpu/drm/msm/dp/dp_drm.h     |   1 +
 drivers/gpu/drm/msm/dp/dp_reg.h     |   2 +-
 7 files changed, 187 insertions(+), 440 deletions(-)
---
base-commit: 8290d37ad2b087bbcfe65fa5bcaf260e184b250a
change-id: 20250523-hpd-refactor-74e25b55620a

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