[PATCH v6 00/18] Add HPD support for Rockchip Analogix DP

[Damon Ding <damon.ding@rock-chips.com>]

This series improves the HPD (Hotplug Detect) interrupt handling in
the Analogix DP driver to enable reliable native HPD pin detection on
Rockchip platforms, and introduces platform-specific HPD detection
schemes with fine-grained interrupt control.

On Rockchip platforms, the Analogix DP native HPD pin IRQ requires the
DP controller to remain powered, clocked and initialized to generate
plug/unplug interrupts. The previous driver enabled/disabled IRQ during
bridge enable/disable, which left no HPD detection when the display
pipeline was inactive. Additionally, the interrupt mute/unmute/clear
routines operated on all HPD interrupt bits unconditionally, lacking
the granularity needed for per-event control.

The series reorganizes IRQ and pm_runtime management into bind/unbind,
adds IRQF_ONESHOT to eliminate read-modify-write races on interrupt
mask registers between hardirq and threaded handlers, converts the
interrupt type detection to a bitmask-based scheme for fine-grained
mute/unmute/clear operations, and configures Rockchip platforms to use
the HOTPLUG_CHG interrupt with a 2ms HPD deglitch setting for better
stability.

Furthermore, the next bridge is now resolved into bridge->next_bridge
instead of the platform data field, the forced connected-status logic
is restricted to panel endpoints based on the bridge chain, and HPD
events from downstream bridges (e.g. display-connector with hpd-gpios)
are handled through the .hpd_notify callback. The DRM_BRIDGE_OP_HPD
capability and the hotplug IRQ are only enabled for the platforms
which actually support hotplug detection, and the fixed panels are
excluded from the hotplug reporting.

Tested on RK3576 with both native HPD pin and GPIO HPD configurations.

Native HPD pin mode:

  &edp {
      status = "okay";
      pinctrl-names = "default";
      pinctrl-0 = <&edp_txm0_pins>;
  };

GPIO HPD mode:

  &edp {
      status = "okay";
      pinctrl-names = "default";
      pinctrl-0 = <&edp0_hpd>;
      hpd-gpios = <&gpio4 RK_PC1 GPIO_ACTIVE_HIGH>;
  };

  &pinctrl {
      edp {
          edp0_hpd: edp0-hpd {
              rockchip,pins = <4 RK_PC1 0 &pcfg_pull_none>;
          };
      };
  };

Display-connector mode (DP connector without HPD GPIO):

  &edp_out_conn {
      remote-endpoint = <&dp_con_in>;
  };

  dp-con {
      compatible = "dp-connector";
      label = "DP OUT";
      type = "full-size";

      port {
          dp_con_in: endpoint {
              remote-endpoint = <&edp_out_conn>;
          };
      };
  };

Display-connector mode (DP connector with HPD GPIO):

  dp-con {
      compatible = "dp-connector";
      label = "DP OUT";
      type = "full-size";
      pinctrl-0 = <&edp0_hpd>;
      pinctrl-names = "default";
      hpd-gpios = <&gpio4 RK_PC1 GPIO_ACTIVE_HIGH>;

      port {
          dp_con_in: endpoint {
              remote-endpoint = <&edp_out_conn>;
          };
      };
  };

All four configurations detect cable plug/unplug events correctly.

Damon Ding (18):
  drm/bridge: Select VIDEOMODE_HELPERS for DRM_OF_DISPLAY_MODE_BRIDGE
  drm/bridge: analogix_dp: Use bridge->next_bridge instead of plat_data
    field
  drm/bridge: analogix_dp: Restrict forced connected status to panel
    endpoints
  drm/bridge: analogix_dp: Return bitmask from
    analogix_dp_get_irq_type()
  drm/bridge: analogix_dp: Check all negative return values for
    &analogix_dp_device.irq
  drm/bridge: analogix_dp: Add IRQF_ONESHOT and simplify IRQ handling
  drm/bridge: analogix_dp: Extend clear_hotplug_interrupts to accept IRQ
    bitmask
  drm/bridge: analogix_dp: Extend mute/unmute HPD interrupts to accept
    irq bitmask
  drm/bridge: analogix_dp: Simplify analogix_dp_config_interrupt()
  drm/bridge: analogix_dp: Use platform-specific HPD detection scheme
  drm/bridge: analogix_dp: Skip native HPD interrupt ops for GPIO HPD
  drm/rockchip: analogix_dp: Unbind bridge when connector init fails
  drm/exynos: exynos_dp: Unbind bridge when connector init fails
  drm/bridge: analogix_dp: Move IRQ enable/disable to bind/unbind
  drm/bridge: analogix_dp: Manage pm runtime and IRQ for native HPD pin
    detection
  drm/bridge: analogix_dp: Declare DRM_BRIDGE_OP_HPD for hotplug
    reporting
  drm/bridge: analogix_dp: Handle HPD notification from downstream
    bridge
  MAINTAINERS: Add entry for Analogix DP controller bridge

 MAINTAINERS                                   |  11 +
 drivers/gpu/drm/bridge/Kconfig                |   1 +
 drivers/gpu/drm/bridge/analogix/Kconfig       |   1 +
 .../drm/bridge/analogix/analogix_dp_core.c    | 240 ++++++++++++++----
 .../drm/bridge/analogix/analogix_dp_core.h    |  15 +-
 .../gpu/drm/bridge/analogix/analogix_dp_reg.c | 153 +++++++----
 drivers/gpu/drm/exynos/Kconfig                |   1 -
 drivers/gpu/drm/exynos/exynos_dp.c            |  16 +-
 .../gpu/drm/rockchip/analogix_dp-rockchip.c   |   1 +
 include/drm/bridge/analogix_dp.h              |   1 -
 10 files changed, 313 insertions(+), 127 deletions(-)

---

Changes in v2:
- Split IRQ enable/disable logic, handle native HPD pin and
  GPIO/force-HPD modes separately to avoid unbalanced enable_irq()
  calls. (Sashiko)
- Add separate patch for IRQF_ONESHOT to resolve interrupt mask issues
  triggered by interrupt preemption. (Sashiko)
- Update commit messages to align with newly added IRQF_ONESHOT related
  commit.
- Move ANALOGIX_DP_HPD_DEGLITCH_L/ANALOGIX_DP_HPD_DEGLITCH_H configs to
  analogix_dp_reset().
- Add new patch to restrict the forced connected-status shortcut to
  panel endpoints only, allowing DP connector bridges to rely on HPD
  detection. (Reported by Heiko Stuebner)
- Add new patch to handle HPD notification from downstream bridges
  (e.g., display-connector with hpd-gpios).

Changes in v3:
- Reorder the series: convert the IRQ handling to a bitmask and add
  IRQF_ONESHOT before moving IRQ enable/disable to bind/unbind.
- Add new patch to check all negative return values for
  &analogix_dp_device.irq and propagate the actual error code. (Sashiko)
- Rename macro HPD_IRQ to HPD_IRQ_ALL to avoid confusion with the
  DP specification IRQ_HPD, extract the irq_type-to-register bit
  mapping into a shared helper, and drop the unused
  COMMON_INT_4_HPD_IRQ macro.
- Simplify commit messages across the series.
- Add new patch to use bridge->next_bridge instead of the plat_data
  field, resolving the next bridge in
  analogix_dp_aux_done_probing(). (Suggested by Heiko Stuebner)
- Report panel endpoints as always connected from
  analogix_dp_get_plug_in_status() via force_connected_mode, computed
  from the bridge chain at attach time.
- Determine the hpd notify mode from DRM_BRIDGE_OP_HPD on downstream
  bridges that lack DRM_BRIDGE_OP_DETECT.
- Add a MAINTAINERS entry for the Analogix DP controller bridge.

Changes in v4:
- Add Tested-by tag from Heiko.
- Rebase onto latest tree, picking up the two related patch series [0][1].

[0] https://lore.kernel.org/all/20260915-drm-bridge-drm_panel-cleanup-v4-0-30401d9406f3@bootlin.com/
[1] https://lore.kernel.org/all/20260916-drm-bridge-every-panel-v3-0-83afb4f1a707@bootlin.com/

Changes in v5:
- Add four new patches:
  - Select VIDEOMODE_HELPERS for DRM_OF_DISPLAY_MODE_BRIDGE to fix
    the undefined references for non-Exynos users.
  - Unbind the bridge when drm_bridge_connector_init() fails on the
    Rockchip and Exynos platforms.
  - Declare DRM_BRIDGE_OP_HPD on the Analogix DP bridge and report
    the hotplug events via drm_bridge_hpd_notify().
- Move the next_bridge resolving patch and the forced connected
  status restriction to the front of the series.
- Use a pure threaded IRQ handler and hold runtime PM references in
  the IRQ thread and the detect paths. (Sashiko)
- Limit the runtime PM holding to the RK3576/RK3588 platforms and
  exclude the boards with a fixed panel. (Sashiko)
- Fix the display timings leak in analogix_dp_aux_done_probing().
  (Sashiko)
- Change the type of &analogix_dp_device.irq to int to fix the dead
  dp->irq < 0 check. (Sashiko)
- Rebase onto the latest drm-misc-next.

Changes in v6:
- Skip the runtime PM reference in the IRQ thread for the GPIO HPD
  mode, since it only reads the GPIO level. (Sashiko)
- Enable the hotplug IRQ only for the platforms which support hotplug
  detection (the GPIO HPD mode, or the native HPD mode on RK3576 and
  RK3588). (Sashiko)
- Exclude the force-connected and force-HPD modes from the hotplug
  detection support check. (Sashiko)
- Declare DRM_BRIDGE_OP_HPD only for the platforms which support
  hotplug detection, since the drm core stops polling the connector
  once DRM_BRIDGE_OP_HPD is declared. (Sashiko)
- Return the cached connection status instead of connector->status
  from analogix_dp_bridge_detect(), as connector->status may still be
  unknown before the first HPD notification or stale after the sysfs
  state forcing. (Sashiko)
- Add Tested-by tags from Heiko and Marek.

-- 
2.34.1