[PATCH v3 00/14] Add HPD support for Rockchip Analogix DP

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

Rebase after the following two patch series:
[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/

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.

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.

======
In the previous version [2], Heiko reported that the Analogix DP
connector state could not be retrieved correctly after probe. With the
current v3 series, analysis shows that the connector hotplug events are
now reported accurately:

1) When the display-connector bridge has hpd-gpios configured, its
   .hpd_enable() callback schedules the HPD work, which triggers the
   .hpd_notify() callbacks of all bridges in the chain. The following
   call stack reports the event during binding and invokes the Analogix
   DP .hpd_notify() callback:

   rockchip_drm_bind()
     -> drm_kms_helper_poll_init()
       -> drm_bridge_connector_enable_hpd()
         -> schedule_work(&conn->hpd_work)
           -> drm_bridge_connector_handle_hpd()
             -> drm_kms_helper_connector_hotplug_event()

2) The local test environment had CONFIG_DRM_FBDEV_EMULATION enabled,
   where the DRM FBDEV framework called the Analogix DP .detect()
   callback to fetch the initial connector state, which masked the
   problem:

   rockchip_drm_bind()
     -> drm_fbdev_client_setup()
       -> drm_fb_helper_initial_config()
         -> drm_helper_probe_single_connector_modes()
           -> analogix_dp_bridge_detect()

3) With CONFIG_DRM_FBDEV_EMULATION disabled, the path in 1) still
   triggers and reports the HPD events as expected.

[2] https://lore.kernel.org/all/20260804081717.741404-1-damon.ding@rock-chips.com/
======

Damon Ding (14):
  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/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: Use bridge->next_bridge instead of plat_data
    field
  drm/bridge: analogix_dp: Restrict forced connected status to panel
    endpoints
  drm/bridge: analogix_dp: Handle HPD notification from downstream
    bridge
  MAINTAINERS: Add entry for Analogix DP controller bridge

 MAINTAINERS                                   |  11 ++
 .../drm/bridge/analogix/analogix_dp_core.c    | 153 ++++++++++++-----
 .../drm/bridge/analogix/analogix_dp_core.h    |  13 +-
 .../gpu/drm/bridge/analogix/analogix_dp_reg.c | 156 ++++++++++++------
 drivers/gpu/drm/exynos/exynos_dp.c            |  15 +-
 include/drm/bridge/analogix_dp.h              |   1 -
 6 files changed, 233 insertions(+), 116 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.

-- 
2.34.1