[PATCH v4 0/8] drm: handle IRQ_HPD events correctly

[PATCH v4 0/8] drm: handle IRQ_HPD events correctly

[Dmitry Baryshkov]

Both DisplayPort and HDMI standards define a way for the Sink / display
to notify the Source / host about some kinds of events. In case of HDMI
it's as simple as singnalling changes to the EDID. In case of
DisplayPort it's more complicated and requires actual checking of the
DPCD registers.

Currently USB-C drivers don't have a way to deliver the IRQ_HPD
notifications, leading to missing MST notifications. Provide necessary
plumbing to let IRQ_HPD events be passed to the DisplayPort drivers.

Note: the Yoga C630 UCSI driver and Acer Aspire1 EC driver are not yet
enabled to send the IRQ_HPD events. Both of them would need some more
reverse engineering to find out how the event is being reported by the
EC.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
Changes in v4:
- Renamed drm_connector_oob_hotplug_event() to
  drm_connector_dp_oob_status() (Maxime)
- Reworked commit messages, explaining what it is about (Bjorn)
- Rearranged commits, making them a bit more logical.
- Link to v3: https://patch.msgid.link/20260421-hpd-irq-events-v3-0-44d2bf40dfc2@oss.qualcomm.com

Changes in v3:
- Fixed build error if aux bridges are disabled (Intel GFX CI)
- Link to v2: https://patch.msgid.link/20260420-hpd-irq-events-v2-0-402ffe27e9e9@oss.qualcomm.com

Changes in v2:
- Change irq_hpd arg to be an enum, possibly desribing other uses (Toni)
- Account for that, chaning the API accordingly (with_irq -> extra,
  etc.)
- Wire up AUX bridge notifications
- Link to v1: https://patch.msgid.link/20260416-hpd-irq-events-v1-0-1ab1f1cfb2b2@oss.qualcomm.com

To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
To: Maxime Ripard <mripard@kernel.org>
To: Thomas Zimmermann <tzimmermann@suse.de>
To: David Airlie <airlied@gmail.com>
To: Simona Vetter <simona@ffwll.ch>
To: Heikki Krogerus <heikki.krogerus@linux.intel.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Andrzej Hajda <andrzej.hajda@intel.com>
To: Neil Armstrong <neil.armstrong@linaro.org>
To: Robert Foss <rfoss@kernel.org>
To: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
To: Jonas Karlman <jonas@kwiboo.se>
To: Jernej Skrabec <jernej.skrabec@gmail.com>
To: Luca Ceresoli <luca.ceresoli@bootlin.com>
To: Jani Nikula <jani.nikula@linux.intel.com>
To: Rodrigo Vivi <rodrigo.vivi@intel.com>
To: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
To: Tvrtko Ursulin <tursulin@ursulin.net>
To: Francesco Dolcini <francesco@dolcini.it>
To: Kevin Hilman <khilman@baylibre.com>
To: Jerome Brunet <jbrunet@baylibre.com>
To: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
To: Rob Clark <robin.clark@oss.qualcomm.com>
To: Dmitry Baryshkov <lumag@kernel.org>
To: Abhinav Kumar <abhinav.kumar@linux.dev>
To: Jessica Zhang <jesszhan0024@gmail.com>
To: Sean Paul <sean@poorly.run>
To: Marijn Suijten <marijn.suijten@somainline.org>
To: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
To: Bjorn Andersson <andersson@kernel.org>
To: Konrad Dybcio <konradybcio@kernel.org>
To: Pengyu Luo <mitltlatltl@gmail.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Cc: intel-gfx@lists.freedesktop.org
Cc: intel-xe@lists.freedesktop.org
Cc: linux-amlogic@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-arm-msm@vger.kernel.org
Cc: freedreno@lists.freedesktop.org

---
Dmitry Baryshkov (8):
      drm/connector: report out-of-band IRQ_HPD events
      drm/connector: pass down IRQ_HPD to the drivers
      drm/bridge: aux-hpd: let drivers pass IRQ_HPD events
      drm/bridge: pass extra events to the HPD callback
      drm/bridge: pass down IRQ_HPD to the drivers
      drm/msm: dp: handle the IRQ_HPD events reported by USB-C
      soc: qcom: pmic-glink-altmode: pass down HPD_IRQ events
      usb: typec: ucsi: huawei-gaokun: pass down HPD_IRQ events

 drivers/gpu/drm/bridge/aux-hpd-bridge.c        | 11 +++++----
 drivers/gpu/drm/bridge/chrontel-ch7033.c       |  3 ++-
 drivers/gpu/drm/bridge/lontium-lt8912b.c       |  3 ++-
 drivers/gpu/drm/bridge/lontium-lt9611uxc.c     |  3 ++-
 drivers/gpu/drm/bridge/ti-tfp410.c             |  3 ++-
 drivers/gpu/drm/display/drm_bridge_connector.c | 22 ++++++++++--------
 drivers/gpu/drm/drm_bridge.c                   | 20 ++++++++++-------
 drivers/gpu/drm/drm_connector.c                | 22 ++++++++++--------
 drivers/gpu/drm/i915/display/intel_dp.c        |  3 ++-
 drivers/gpu/drm/meson/meson_encoder_hdmi.c     |  3 ++-
 drivers/gpu/drm/msm/dp/dp_display.c            | 10 +++++----
 drivers/gpu/drm/msm/dp/dp_drm.h                |  3 ++-
 drivers/gpu/drm/omapdrm/dss/hdmi4.c            |  3 ++-
 drivers/soc/qcom/pmic_glink_altmode.c          |  6 ++++-
 drivers/usb/typec/altmodes/displayport.c       | 23 ++++++++++++-------
 drivers/usb/typec/ucsi/ucsi_huawei_gaokun.c    | 11 +++++----
 include/drm/bridge/aux-bridge.h                | 13 +++++++++--
 include/drm/drm_bridge.h                       | 31 +++++++++++++++++++++-----
 include/drm/drm_connector.h                    | 24 +++++++++++++++++---
 19 files changed, 152 insertions(+), 65 deletions(-)
---
base-commit: 6e845bcb78c95af935094040bd4edc3c2b6dd784
change-id: 20260414-hpd-irq-events-e72bc076a5f1

Best regards,
--  
With best wishes
Dmitry

[PATCH v4 1/8] drm/connector: report out-of-band IRQ_HPD events

[Dmitry Baryshkov]

The DisplayPort standard defines a special kind of events called IRQ.
These events are used to notify DP Source about the events on the Sink
side. It is extremely important for DP MST handling, where the MST
events are reported through this IRQ.

In case of the USB-C DP AltMode there is no actual HPD pulse, but the
events are reported through the bits in the AltMode VDOs.

Rename drm_connector_oob_hotplug_event() to drm_connector_dp_oob_status()
and extend its interface to report IRQ events to the DisplayPort Sink
drivers.

Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/gpu/drm/drm_connector.c          | 20 ++++++++++++--------
 drivers/usb/typec/altmodes/displayport.c | 23 +++++++++++++++--------
 include/drm/drm_connector.h              | 21 +++++++++++++++++++--
 3 files changed, 46 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index 3fa4d2082cd7..bb128dd0263a 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -3502,20 +3502,24 @@ struct drm_connector *drm_connector_find_by_fwnode(struct fwnode_handle *fwnode)
 }
 
 /**
- * drm_connector_oob_hotplug_event - Report out-of-band hotplug event to connector
+ * drm_connector_dp_oob_status - Report out-of-band hotplug event to DisplayPort connector
  * @connector_fwnode: fwnode_handle to report the event on
  * @status: hot plug detect logical state
+ * @extra_status: additional information provided by the sink without changing
+ * the HPD state (or in addition to such a change).
  *
- * On some hardware a hotplug event notification may come from outside the display
- * driver / device. An example of this is some USB Type-C setups where the hardware
- * muxes the DisplayPort data and aux-lines but does not pass the altmode HPD
- * status bit to the GPU's DP HPD pin.
+ * In some cases when DisplayPort signals are being routed through the USB
+ * Type-C port the hotplug event notifications come from outside of the display
+ * driver / device. In this case hardware muxes the DisplayPort data and
+ * AUX-lines but does not pass the altmode HPD status bit to the GPU's DP HPD
+ * pin.
  *
  * This function can be used to report these out-of-band events after obtaining
  * a drm_connector reference through calling drm_connector_find_by_fwnode().
  */
-void drm_connector_oob_hotplug_event(struct fwnode_handle *connector_fwnode,
-				     enum drm_connector_status status)
+void drm_connector_dp_oob_status(struct fwnode_handle *connector_fwnode,
+				 enum drm_connector_status status,
+				 enum drm_connector_status_extra extra_status)
 {
 	struct drm_connector *connector;
 
@@ -3528,7 +3532,7 @@ void drm_connector_oob_hotplug_event(struct fwnode_handle *connector_fwnode,
 
 	drm_connector_put(connector);
 }
-EXPORT_SYMBOL(drm_connector_oob_hotplug_event);
+EXPORT_SYMBOL(drm_connector_dp_oob_status);
 
 
 /**
diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index 263a89c5f324..ff3659b8f5a2 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -187,9 +187,11 @@ static int dp_altmode_status_update(struct dp_altmode *dp)
 				dp->pending_irq_hpd = true;
 		}
 	} else {
-		drm_connector_oob_hotplug_event(dp->connector_fwnode,
+		drm_connector_dp_oob_status(dp->connector_fwnode,
 						hpd ? connector_status_connected :
-						      connector_status_disconnected);
+						      connector_status_disconnected,
+						(hpd && irq_hpd) ? DRM_CONNECTOR_DP_IRQ_HPD :
+								   DRM_CONNECTOR_NO_EXTRA_STATUS);
 		dp->hpd = hpd;
 		sysfs_notify(&dp->alt->dev.kobj, "displayport", "hpd");
 		if (hpd && irq_hpd) {
@@ -211,8 +213,11 @@ static int dp_altmode_configured(struct dp_altmode *dp)
 	 * configuration is complete to signal HPD.
 	 */
 	if (dp->pending_hpd) {
-		drm_connector_oob_hotplug_event(dp->connector_fwnode,
-						connector_status_connected);
+		drm_connector_dp_oob_status(dp->connector_fwnode,
+						connector_status_connected,
+						dp->pending_irq_hpd ?
+						DRM_CONNECTOR_DP_IRQ_HPD :
+						DRM_CONNECTOR_NO_EXTRA_STATUS);
 		sysfs_notify(&dp->alt->dev.kobj, "displayport", "hpd");
 		dp->pending_hpd = false;
 		if (dp->pending_irq_hpd) {
@@ -396,8 +401,9 @@ static int dp_altmode_vdm(struct typec_altmode *alt,
 			dp->data.status = 0;
 			dp->data.conf = 0;
 			if (dp->hpd) {
-				drm_connector_oob_hotplug_event(dp->connector_fwnode,
-								connector_status_disconnected);
+				drm_connector_dp_oob_status(dp->connector_fwnode,
+								connector_status_disconnected,
+								DRM_CONNECTOR_NO_EXTRA_STATUS);
 				dp->hpd = false;
 				sysfs_notify(&dp->alt->dev.kobj, "displayport", "hpd");
 			}
@@ -828,8 +834,9 @@ void dp_altmode_remove(struct typec_altmode *alt)
 	typec_altmode_put_plug(dp->plug_prime);
 
 	if (dp->connector_fwnode) {
-		drm_connector_oob_hotplug_event(dp->connector_fwnode,
-						connector_status_disconnected);
+		drm_connector_dp_oob_status(dp->connector_fwnode,
+						connector_status_disconnected,
+						DRM_CONNECTOR_NO_EXTRA_STATUS);
 
 		fwnode_handle_put(dp->connector_fwnode);
 	}
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 5ad62c207d00..105da7c94910 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -91,6 +91,22 @@ enum drm_connector_status {
 	connector_status_unknown = 3,
 };
 
+/**
+ * enum drm_connector_status_extra - additional events sent by the sink /
+ * display together or in replacement of the HPD status changes.
+ */
+enum drm_connector_status_extra {
+	/**
+	 * @DRM_CONNECTOR_NO_EXTRA_STATUS: No additional status reported.
+	 */
+	DRM_CONNECTOR_NO_EXTRA_STATUS,
+	/**
+	 * @DRM_CONNECTOR_DP_IRQ_HPD: DisplayPort Sink has sent the
+	 * IRQ_HPD (either by the HPD short pulse or via the AltMode event).
+	 */
+	DRM_CONNECTOR_DP_IRQ_HPD,
+};
+
 /**
  * enum drm_connector_registration_state - userspace registration status for
  * a &drm_connector
@@ -2520,8 +2536,9 @@ drm_connector_is_unregistered(struct drm_connector *connector)
 		DRM_CONNECTOR_UNREGISTERED;
 }
 
-void drm_connector_oob_hotplug_event(struct fwnode_handle *connector_fwnode,
-				     enum drm_connector_status status);
+void drm_connector_dp_oob_status(struct fwnode_handle *connector_fwnode,
+				 enum drm_connector_status status,
+				 enum drm_connector_status_extra extra_status);
 const char *drm_get_connector_type_name(unsigned int connector_type);
 const char *drm_get_connector_status_name(enum drm_connector_status status);
 const char *drm_get_subpixel_order_name(enum subpixel_order order);

-- 
2.47.3

[PATCH v4 2/8] drm/connector: pass down IRQ_HPD to the drivers

[Dmitry Baryshkov]

The DisplayPort standard defines a special kind of HPD events called
IRQ_HPD. These events are used to notify DP Source about the events on
the Sink side.

Extend drm_connector_funcs::oob_hotplug_event() to pass the
notifications about the IRQ_HPD events down to the individual drivers,
letting them handle those as required.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/gpu/drm/display/drm_bridge_connector.c | 17 ++++++++++-------
 drivers/gpu/drm/drm_connector.c                |  2 +-
 drivers/gpu/drm/i915/display/intel_dp.c        |  3 ++-
 include/drm/drm_connector.h                    |  3 ++-
 4 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
index 649969fca141..046efd913064 100644
--- a/drivers/gpu/drm/display/drm_bridge_connector.c
+++ b/drivers/gpu/drm/display/drm_bridge_connector.c
@@ -141,7 +141,8 @@ struct drm_bridge_connector {
  */
 
 static void drm_bridge_connector_hpd_notify(struct drm_connector *connector,
-					    enum drm_connector_status status)
+					    enum drm_connector_status status,
+					    enum drm_connector_status_extra extra_status)
 {
 	struct drm_bridge_connector *bridge_connector =
 		to_drm_bridge_connector(connector);
@@ -154,7 +155,8 @@ static void drm_bridge_connector_hpd_notify(struct drm_connector *connector,
 }
 
 static void drm_bridge_connector_handle_hpd(struct drm_bridge_connector *drm_bridge_connector,
-					    enum drm_connector_status status)
+					    enum drm_connector_status status,
+					    enum drm_connector_status_extra extra_status)
 {
 	struct drm_connector *connector = &drm_bridge_connector->base;
 	struct drm_device *dev = connector->dev;
@@ -163,7 +165,7 @@ static void drm_bridge_connector_handle_hpd(struct drm_bridge_connector *drm_bri
 	connector->status = status;
 	mutex_unlock(&dev->mode_config.mutex);
 
-	drm_bridge_connector_hpd_notify(connector, status);
+	drm_bridge_connector_hpd_notify(connector, status, extra_status);
 
 	drm_kms_helper_connector_hotplug_event(connector);
 }
@@ -171,16 +173,17 @@ static void drm_bridge_connector_handle_hpd(struct drm_bridge_connector *drm_bri
 static void drm_bridge_connector_hpd_cb(void *cb_data,
 					enum drm_connector_status status)
 {
-	drm_bridge_connector_handle_hpd(cb_data, status);
+	drm_bridge_connector_handle_hpd(cb_data, status, DRM_CONNECTOR_NO_EXTRA_STATUS);
 }
 
 static void drm_bridge_connector_oob_hotplug_event(struct drm_connector *connector,
-						   enum drm_connector_status status)
+						   enum drm_connector_status status,
+						   enum drm_connector_status_extra extra_status)
 {
 	struct drm_bridge_connector *bridge_connector =
 		to_drm_bridge_connector(connector);
 
-	drm_bridge_connector_handle_hpd(bridge_connector, status);
+	drm_bridge_connector_handle_hpd(bridge_connector, status, extra_status);
 }
 
 static void drm_bridge_connector_enable_hpd(struct drm_connector *connector)
@@ -223,7 +226,7 @@ drm_bridge_connector_detect(struct drm_connector *connector, bool force)
 		if (hdmi)
 			drm_atomic_helper_connector_hdmi_hotplug(connector, status);
 
-		drm_bridge_connector_hpd_notify(connector, status);
+		drm_bridge_connector_hpd_notify(connector, status, DRM_CONNECTOR_NO_EXTRA_STATUS);
 	} else {
 		switch (connector->connector_type) {
 		case DRM_MODE_CONNECTOR_DPI:
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
index bb128dd0263a..d99019fdea9c 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -3528,7 +3528,7 @@ void drm_connector_dp_oob_status(struct fwnode_handle *connector_fwnode,
 		return;
 
 	if (connector->funcs->oob_hotplug_event)
-		connector->funcs->oob_hotplug_event(connector, status);
+		connector->funcs->oob_hotplug_event(connector, status, extra_status);
 
 	drm_connector_put(connector);
 }
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 85d3aa3b9894..31acb3129723 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -6990,7 +6990,8 @@ static int intel_dp_connector_atomic_check(struct drm_connector *_connector,
 }
 
 static void intel_dp_oob_hotplug_event(struct drm_connector *_connector,
-				       enum drm_connector_status hpd_state)
+				       enum drm_connector_status hpd_state,
+				       enum drm_connector_status_extra extra_status)
 {
 	struct intel_connector *connector = to_intel_connector(_connector);
 	struct intel_display *display = to_intel_display(connector);
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 105da7c94910..5784bb9c4021 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -1720,7 +1720,8 @@ struct drm_connector_funcs {
 	 * has been received from a source outside the display driver / device.
 	 */
 	void (*oob_hotplug_event)(struct drm_connector *connector,
-				  enum drm_connector_status status);
+				  enum drm_connector_status status,
+				  enum drm_connector_status_extra extra_status);
 
 	/**
 	 * @debugfs_init:

-- 
2.47.3

[PATCH v4 3/8] drm/bridge: aux-hpd: let drivers pass IRQ_HPD events

[Dmitry Baryshkov]

The DisplayPort standard defines a special kind of HPD events called
IRQ_HPD. These events are used to notify DP Source about the events on
the Sink side.

Let users of aux-hpd, the UCSI and PMIC GLINK drivers pass the IRQ_HPD
events to the DisplayPort drivers.

The drm_aux_hpd_bridge_notify() is kept to ease merging of the series,
preventing extra cross-tree merges. It will be removed once all
drivers are converted. The drm_bridge_hpd_notify() function is kept for
the drivers which only care about the connector status and will always
pass DRM_CONNECTOR_NO_EXTRA_STATUS as the extra status.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/gpu/drm/bridge/aux-hpd-bridge.c | 11 +++++++----
 drivers/gpu/drm/drm_bridge.c            | 15 +++++++++------
 include/drm/bridge/aux-bridge.h         | 13 +++++++++++--
 include/drm/drm_bridge.h                | 22 ++++++++++++++++++++--
 4 files changed, 47 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/bridge/aux-hpd-bridge.c b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
index f02a38a2638a..0e2f0b046121 100644
--- a/drivers/gpu/drm/bridge/aux-hpd-bridge.c
+++ b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
@@ -136,16 +136,19 @@ struct device *drm_dp_hpd_bridge_register(struct device *parent, struct device_n
 EXPORT_SYMBOL_GPL(drm_dp_hpd_bridge_register);
 
 /**
- * drm_aux_hpd_bridge_notify - notify hot plug detection events
+ * drm_aux_hpd_bridge_notify_extra - notify hot plug detection events
  * @dev: device created for the HPD bridge
  * @status: output connection status
+ * @extra_status: extra status bits like DRM_CONNECTOR_DP_IRQ_HPD
  *
  * A wrapper around drm_bridge_hpd_notify() that is used to report hot plug
  * detection events for bridges created via drm_dp_hpd_bridge_register().
  *
  * This function shall be called in a context that can sleep.
  */
-void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status)
+void drm_aux_hpd_bridge_notify_extra(struct device *dev,
+				     enum drm_connector_status status,
+				     enum drm_connector_status_extra extra_status)
 {
 	struct auxiliary_device *adev = to_auxiliary_dev(dev);
 	struct drm_aux_hpd_bridge_data *data = auxiliary_get_drvdata(adev);
@@ -153,9 +156,9 @@ void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status sta
 	if (!data)
 		return;
 
-	drm_bridge_hpd_notify(&data->bridge, status);
+	drm_bridge_hpd_notify_extra(&data->bridge, status, extra_status);
 }
-EXPORT_SYMBOL_GPL(drm_aux_hpd_bridge_notify);
+EXPORT_SYMBOL_GPL(drm_aux_hpd_bridge_notify_extra);
 
 static int drm_aux_hpd_bridge_attach(struct drm_bridge *bridge,
 				     struct drm_encoder *encoder,
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 687b36eea0c7..84e55db5c1fe 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -1495,25 +1495,28 @@ void drm_bridge_hpd_disable(struct drm_bridge *bridge)
 EXPORT_SYMBOL_GPL(drm_bridge_hpd_disable);
 
 /**
- * drm_bridge_hpd_notify - notify hot plug detection events
+ * drm_bridge_hpd_notify_extra - notify hot plug detection and sink IRQ events
  * @bridge: bridge control structure
  * @status: output connection status
+ * @extra_status: additional status recorded by the sink
  *
  * Bridge drivers shall call this function to report hot plug events when they
- * detect a change in the output status, when hot plug detection has been
- * enabled by drm_bridge_hpd_enable().
+ * detect a change in the output status or when the sink has reported extra HPD
+ * status events (like the IRQ_HPD in case of the DisplayPort), when hot plug
+ * detection has been enabled by drm_bridge_hpd_enable().
  *
  * This function shall be called in a context that can sleep.
  */
-void drm_bridge_hpd_notify(struct drm_bridge *bridge,
-			   enum drm_connector_status status)
+void drm_bridge_hpd_notify_extra(struct drm_bridge *bridge,
+				 enum drm_connector_status status,
+				 enum drm_connector_status_extra extra_status)
 {
 	mutex_lock(&bridge->hpd_mutex);
 	if (bridge->hpd_cb)
 		bridge->hpd_cb(bridge->hpd_data, status);
 	mutex_unlock(&bridge->hpd_mutex);
 }
-EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify);
+EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify_extra);
 
 #ifdef CONFIG_OF
 /**
diff --git a/include/drm/bridge/aux-bridge.h b/include/drm/bridge/aux-bridge.h
index c2f5a855512f..f9a86886b0df 100644
--- a/include/drm/bridge/aux-bridge.h
+++ b/include/drm/bridge/aux-bridge.h
@@ -25,7 +25,9 @@ struct auxiliary_device *devm_drm_dp_hpd_bridge_alloc(struct device *parent, str
 int devm_drm_dp_hpd_bridge_add(struct device *dev, struct auxiliary_device *adev);
 struct device *drm_dp_hpd_bridge_register(struct device *parent,
 					  struct device_node *np);
-void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status);
+void drm_aux_hpd_bridge_notify_extra(struct device *dev,
+				     enum drm_connector_status status,
+				     enum drm_connector_status_extra extra_status);
 #else
 static inline struct auxiliary_device *devm_drm_dp_hpd_bridge_alloc(struct device *parent,
 								    struct device_node *np)
@@ -44,9 +46,16 @@ static inline struct device *drm_dp_hpd_bridge_register(struct device *parent,
 	return NULL;
 }
 
-static inline void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status)
+static inline void drm_aux_hpd_bridge_notify_extra(struct device *dev,
+						   enum drm_connector_status status,
+						   enum drm_connector_status_extra extra_status)
 {
 }
 #endif
 
+static inline void drm_aux_hpd_bridge_notify(struct device *dev, enum drm_connector_status status)
+{
+	drm_aux_hpd_bridge_notify_extra(dev, status, DRM_CONNECTOR_NO_EXTRA_STATUS);
+}
+
 #endif
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 4ba3a5deef9a..78b0d83ef2aa 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -1581,8 +1581,26 @@ void drm_bridge_hpd_enable(struct drm_bridge *bridge,
 				      enum drm_connector_status status),
 			   void *data);
 void drm_bridge_hpd_disable(struct drm_bridge *bridge);
-void drm_bridge_hpd_notify(struct drm_bridge *bridge,
-			   enum drm_connector_status status);
+void drm_bridge_hpd_notify_extra(struct drm_bridge *bridge,
+				 enum drm_connector_status status,
+				 enum drm_connector_status_extra extra_status);
+
+/**
+ * drm_bridge_hpd_notify - notify hot plug detection events
+ * @bridge: bridge control structure
+ * @status: output connection status
+ *
+ * Bridge drivers shall call this function to report hot plug events when they
+ * detect a change in the output status, when hot plug detection has been
+ * enabled by drm_bridge_hpd_enable().
+ *
+ * This function shall be called in a context that can sleep.
+ */
+static inline void drm_bridge_hpd_notify(struct drm_bridge *bridge,
+					 enum drm_connector_status status)
+{
+	drm_bridge_hpd_notify_extra(bridge, status, DRM_CONNECTOR_NO_EXTRA_STATUS);
+}
 
 #ifdef CONFIG_DRM_PANEL_BRIDGE
 bool drm_bridge_is_panel(const struct drm_bridge *bridge);

-- 
2.47.3

[PATCH v4 4/8] drm/bridge: pass extra events to the HPD callback

[Dmitry Baryshkov]

The DisplayPort standard defines a special kind of HPD events called
IRQ_HPD. These events are used to notify DP Source about the events on
the Sink side.

Bridge drivers report these events through the
drm_bridge_hpd_notify_extra(). Pass down the extra status to the HPD
callback, specified during the drm_bridge_hpd_enable(), letting
underlying drivers (e.g. drm_bridge_connector) to receive these events.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/gpu/drm/bridge/chrontel-ch7033.c       | 3 ++-
 drivers/gpu/drm/bridge/lontium-lt8912b.c       | 3 ++-
 drivers/gpu/drm/bridge/ti-tfp410.c             | 3 ++-
 drivers/gpu/drm/display/drm_bridge_connector.c | 5 +++--
 drivers/gpu/drm/drm_bridge.c                   | 5 +++--
 include/drm/drm_bridge.h                       | 6 ++++--
 6 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/bridge/chrontel-ch7033.c b/drivers/gpu/drm/bridge/chrontel-ch7033.c
index a237c65ebd69..35df99b02c9c 100644
--- a/drivers/gpu/drm/bridge/chrontel-ch7033.c
+++ b/drivers/gpu/drm/bridge/chrontel-ch7033.c
@@ -258,7 +258,8 @@ static const struct drm_connector_helper_funcs ch7033_connector_helper_funcs = {
 	.best_encoder = ch7033_connector_best_encoder,
 };
 
-static void ch7033_hpd_event(void *arg, enum drm_connector_status status)
+static void ch7033_hpd_event(void *arg, enum drm_connector_status status,
+			     enum drm_connector_status_extra extra_status)
 {
 	struct ch7033_priv *priv = arg;
 
diff --git a/drivers/gpu/drm/bridge/lontium-lt8912b.c b/drivers/gpu/drm/bridge/lontium-lt8912b.c
index 729b12b67470..b8e643cf1d4d 100644
--- a/drivers/gpu/drm/bridge/lontium-lt8912b.c
+++ b/drivers/gpu/drm/bridge/lontium-lt8912b.c
@@ -505,7 +505,8 @@ static int lt8912_attach_dsi(struct lt8912 *lt)
 	return 0;
 }
 
-static void lt8912_bridge_hpd_cb(void *data, enum drm_connector_status status)
+static void lt8912_bridge_hpd_cb(void *data, enum drm_connector_status status,
+				 enum drm_connector_status_extra extra_status)
 {
 	struct lt8912 *lt = data;
 
diff --git a/drivers/gpu/drm/bridge/ti-tfp410.c b/drivers/gpu/drm/bridge/ti-tfp410.c
index bf4ab4eaf269..e2eedaaa3552 100644
--- a/drivers/gpu/drm/bridge/ti-tfp410.c
+++ b/drivers/gpu/drm/bridge/ti-tfp410.c
@@ -110,7 +110,8 @@ static void tfp410_hpd_work_func(struct work_struct *work)
 		drm_helper_hpd_irq_event(dvi->bridge.dev);
 }
 
-static void tfp410_hpd_callback(void *arg, enum drm_connector_status status)
+static void tfp410_hpd_callback(void *arg, enum drm_connector_status status,
+				enum drm_connector_status_extra extra_status)
 {
 	struct tfp410 *dvi = arg;
 
diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
index 046efd913064..a34643d3ddef 100644
--- a/drivers/gpu/drm/display/drm_bridge_connector.c
+++ b/drivers/gpu/drm/display/drm_bridge_connector.c
@@ -171,9 +171,10 @@ static void drm_bridge_connector_handle_hpd(struct drm_bridge_connector *drm_bri
 }
 
 static void drm_bridge_connector_hpd_cb(void *cb_data,
-					enum drm_connector_status status)
+					enum drm_connector_status status,
+					enum drm_connector_status_extra extra_status)
 {
-	drm_bridge_connector_handle_hpd(cb_data, status, DRM_CONNECTOR_NO_EXTRA_STATUS);
+	drm_bridge_connector_handle_hpd(cb_data, status, extra_status);
 }
 
 static void drm_bridge_connector_oob_hotplug_event(struct drm_connector *connector,
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 84e55db5c1fe..3fd3e7bac588 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -1445,7 +1445,8 @@ EXPORT_SYMBOL_GPL(drm_bridge_edid_read);
  */
 void drm_bridge_hpd_enable(struct drm_bridge *bridge,
 			   void (*cb)(void *data,
-				      enum drm_connector_status status),
+				      enum drm_connector_status status,
+				      enum drm_connector_status_extra extra_status),
 			   void *data)
 {
 	if (!(bridge->ops & DRM_BRIDGE_OP_HPD))
@@ -1513,7 +1514,7 @@ void drm_bridge_hpd_notify_extra(struct drm_bridge *bridge,
 {
 	mutex_lock(&bridge->hpd_mutex);
 	if (bridge->hpd_cb)
-		bridge->hpd_cb(bridge->hpd_data, status);
+		bridge->hpd_cb(bridge->hpd_data, status, extra_status);
 	mutex_unlock(&bridge->hpd_mutex);
 }
 EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify_extra);
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 78b0d83ef2aa..6a5edfda2ddd 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -1260,7 +1260,8 @@ struct drm_bridge {
 	 * @hpd_cb: Hot plug detection callback, registered with
 	 * drm_bridge_hpd_enable().
 	 */
-	void (*hpd_cb)(void *data, enum drm_connector_status status);
+	void (*hpd_cb)(void *data, enum drm_connector_status status,
+		       enum drm_connector_status_extra extra_status);
 	/**
 	 * @hpd_data: Private data passed to the Hot plug detection callback
 	 * @hpd_cb.
@@ -1578,7 +1579,8 @@ const struct drm_edid *drm_bridge_edid_read(struct drm_bridge *bridge,
 					    struct drm_connector *connector);
 void drm_bridge_hpd_enable(struct drm_bridge *bridge,
 			   void (*cb)(void *data,
-				      enum drm_connector_status status),
+				      enum drm_connector_status status,
+				      enum drm_connector_status_extra extra_status),
 			   void *data);
 void drm_bridge_hpd_disable(struct drm_bridge *bridge);
 void drm_bridge_hpd_notify_extra(struct drm_bridge *bridge,

-- 
2.47.3

[PATCH v4 5/8] drm/bridge: pass down IRQ_HPD to the drivers

[Dmitry Baryshkov]

The DisplayPort standard defines a special kind of HPD events called
IRQ_HPD. These events are used to notify DP Source about the events on
the Sink side. Pass down the extra status to the bridge drivers via the
hpd_notify() callback, letting DP bridges to act accordingly.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/gpu/drm/bridge/lontium-lt9611uxc.c     | 3 ++-
 drivers/gpu/drm/display/drm_bridge_connector.c | 2 +-
 drivers/gpu/drm/meson/meson_encoder_hdmi.c     | 3 ++-
 drivers/gpu/drm/msm/dp/dp_display.c            | 3 ++-
 drivers/gpu/drm/msm/dp/dp_drm.h                | 3 ++-
 drivers/gpu/drm/omapdrm/dss/hdmi4.c            | 3 ++-
 include/drm/drm_bridge.h                       | 3 ++-
 7 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/bridge/lontium-lt9611uxc.c b/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
index 9427cc2358ae..8cb17bd0e238 100644
--- a/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
+++ b/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
@@ -429,7 +429,8 @@ static const struct drm_edid *lt9611uxc_bridge_edid_read(struct drm_bridge *brid
 
 static void lt9611uxc_bridge_hpd_notify(struct drm_bridge *bridge,
 					struct drm_connector *connector,
-					enum drm_connector_status status)
+					enum drm_connector_status status,
+					enum drm_connector_status_extra extra_status)
 {
 	const struct drm_edid *drm_edid;
 
diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
index a34643d3ddef..8f7075fd2aa5 100644
--- a/drivers/gpu/drm/display/drm_bridge_connector.c
+++ b/drivers/gpu/drm/display/drm_bridge_connector.c
@@ -150,7 +150,7 @@ static void drm_bridge_connector_hpd_notify(struct drm_connector *connector,
 	/* Notify all bridges in the pipeline of hotplug events. */
 	drm_for_each_bridge_in_chain_scoped(bridge_connector->encoder, bridge) {
 		if (bridge->funcs->hpd_notify)
-			bridge->funcs->hpd_notify(bridge, connector, status);
+			bridge->funcs->hpd_notify(bridge, connector, status, extra_status);
 	}
 }
 
diff --git a/drivers/gpu/drm/meson/meson_encoder_hdmi.c b/drivers/gpu/drm/meson/meson_encoder_hdmi.c
index 55c0601df3c6..4aecf0ffcf75 100644
--- a/drivers/gpu/drm/meson/meson_encoder_hdmi.c
+++ b/drivers/gpu/drm/meson/meson_encoder_hdmi.c
@@ -323,7 +323,8 @@ static int meson_encoder_hdmi_atomic_check(struct drm_bridge *bridge,
 
 static void meson_encoder_hdmi_hpd_notify(struct drm_bridge *bridge,
 					  struct drm_connector *connector,
-					  enum drm_connector_status status)
+					  enum drm_connector_status status,
+					  enum drm_connector_status_extra extra_status)
 {
 	struct meson_encoder_hdmi *encoder_hdmi = bridge_to_meson_encoder_hdmi(bridge);
 
diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index dc6f33809ca5..c0f6a8ff9b99 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -1514,7 +1514,8 @@ void msm_dp_bridge_hpd_disable(struct drm_bridge *bridge)
 
 void msm_dp_bridge_hpd_notify(struct drm_bridge *bridge,
 			      struct drm_connector *connector,
-			      enum drm_connector_status status)
+			      enum drm_connector_status status,
+			      enum drm_connector_status_extra extra_status)
 {
 	struct msm_dp_bridge *msm_dp_bridge = to_dp_bridge(bridge);
 	struct msm_dp *msm_dp_display = msm_dp_bridge->msm_dp_display;
diff --git a/drivers/gpu/drm/msm/dp/dp_drm.h b/drivers/gpu/drm/msm/dp/dp_drm.h
index 041aa026ae2e..4d98e04bb511 100644
--- a/drivers/gpu/drm/msm/dp/dp_drm.h
+++ b/drivers/gpu/drm/msm/dp/dp_drm.h
@@ -43,6 +43,7 @@ void msm_dp_bridge_hpd_enable(struct drm_bridge *bridge);
 void msm_dp_bridge_hpd_disable(struct drm_bridge *bridge);
 void msm_dp_bridge_hpd_notify(struct drm_bridge *bridge,
 			      struct drm_connector *connector,
-			      enum drm_connector_status status);
+			      enum drm_connector_status status,
+			      enum drm_connector_status_extra extra_status);
 
 #endif /* _DP_DRM_H_ */
diff --git a/drivers/gpu/drm/omapdrm/dss/hdmi4.c b/drivers/gpu/drm/omapdrm/dss/hdmi4.c
index e306247ed8a0..d02d432abde4 100644
--- a/drivers/gpu/drm/omapdrm/dss/hdmi4.c
+++ b/drivers/gpu/drm/omapdrm/dss/hdmi4.c
@@ -429,7 +429,8 @@ static void hdmi4_bridge_disable(struct drm_bridge *bridge,
 
 static void hdmi4_bridge_hpd_notify(struct drm_bridge *bridge,
 				    struct drm_connector *connector,
-				    enum drm_connector_status status)
+				    enum drm_connector_status status,
+				    enum drm_connector_status_extra extra_status)
 {
 	struct omap_hdmi *hdmi = drm_bridge_to_hdmi(bridge);
 
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 6a5edfda2ddd..9c4c88024cc5 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -615,7 +615,8 @@ struct drm_bridge_funcs {
 	 */
 	void (*hpd_notify)(struct drm_bridge *bridge,
 			   struct drm_connector *connector,
-			   enum drm_connector_status status);
+			   enum drm_connector_status status,
+			   enum drm_connector_status_extra extra_status);
 
 	/**
 	 * @hpd_enable:

-- 
2.47.3

[PATCH v4 6/8] drm/msm: dp: handle the IRQ_HPD events reported by USB-C

[Dmitry Baryshkov]

The DisplayPort standard defines a special kind of HPD events called
IRQ_HPD. These events are used to notify DP Source about the events on
the Sink side, for example DP MST events.

Let the MSM DisplayPort driver properly track and handle IRQ_HPD
delivered over the OOB events (e.g. from the USB-C AltMode handler).

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/gpu/drm/msm/dp/dp_display.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index c0f6a8ff9b99..743d8fa40dc6 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -1533,11 +1533,12 @@ void msm_dp_bridge_hpd_notify(struct drm_bridge *bridge,
 		   msm_dp_display->connector_type, hpd_link_status, status);
 
 	if (status == connector_status_connected) {
-		if (hpd_link_status == ISR_HPD_REPLUG_COUNT) {
+		if (hpd_link_status == ISR_IRQ_HPD_PULSE_COUNT ||
+		    extra_status == DRM_CONNECTOR_DP_IRQ_HPD) {
+			msm_dp_irq_hpd_handle(dp);
+		} else if (hpd_link_status == ISR_HPD_REPLUG_COUNT) {
 			msm_dp_hpd_unplug_handle(dp);
 			msm_dp_hpd_plug_handle(dp);
-		} else if (hpd_link_status == ISR_IRQ_HPD_PULSE_COUNT) {
-			msm_dp_irq_hpd_handle(dp);
 		} else {
 			msm_dp_hpd_plug_handle(dp);
 		}

-- 
2.47.3

[PATCH v4 7/8] soc: qcom: pmic-glink-altmode: pass down HPD_IRQ events

[Dmitry Baryshkov]

The DisplayPort standard defines a special kind of HPD events called
IRQ_HPD. These events are used to notify DP Source about the events on
the Sink side.

Pass IRQ_HPD events from the firmware to the HPD bridge, letting those
to be delivered to the DisplayPort driver.

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Acked-by: Bjorn Andersson <andersson@kernel.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/soc/qcom/pmic_glink_altmode.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/soc/qcom/pmic_glink_altmode.c b/drivers/soc/qcom/pmic_glink_altmode.c
index 619bad2c27ee..946eb20b8f83 100644
--- a/drivers/soc/qcom/pmic_glink_altmode.c
+++ b/drivers/soc/qcom/pmic_glink_altmode.c
@@ -373,7 +373,11 @@ static void pmic_glink_altmode_worker(struct work_struct *work)
 		else
 			conn_status = connector_status_disconnected;
 
-		drm_aux_hpd_bridge_notify(&alt_port->bridge->dev, conn_status);
+		drm_aux_hpd_bridge_notify_extra(&alt_port->bridge->dev,
+						conn_status,
+						alt_port->hpd_irq ?
+						DRM_CONNECTOR_DP_IRQ_HPD :
+						DRM_CONNECTOR_NO_EXTRA_STATUS);
 	} else if (alt_port->mux_ctrl == MUX_CTRL_STATE_TUNNELING) {
 		if (alt_port->svid == USB_TYPEC_TBT_SID)
 			pmic_glink_altmode_enable_tbt(altmode, alt_port);

-- 
2.47.3

[PATCH v4 8/8] usb: typec: ucsi: huawei-gaokun: pass down HPD_IRQ events

[Dmitry Baryshkov]

The DisplayPort standard defines a special kind of HPD events called
IRQ_HPD. These events are used to notify DP Source about the events on
the Sink side.

Pass IRQ_HPD events from the EC to the HPD bridge, letting those
to be delivered to the DisplayPort driver.

Reviewed-by: Pengyu Luo <mitltlatltl@gmail.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/usb/typec/ucsi/ucsi_huawei_gaokun.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/typec/ucsi/ucsi_huawei_gaokun.c b/drivers/usb/typec/ucsi/ucsi_huawei_gaokun.c
index ca749fde49bd..5e3f887ecbd8 100644
--- a/drivers/usb/typec/ucsi/ucsi_huawei_gaokun.c
+++ b/drivers/usb/typec/ucsi/ucsi_huawei_gaokun.c
@@ -299,10 +299,13 @@ static void gaokun_ucsi_handle_altmode(struct gaokun_ucsi_port *port)
 
 	/* UCSI callback .connector_status() have set orientation */
 	if (port->bridge)
-		drm_aux_hpd_bridge_notify(&port->bridge->dev,
-					  port->hpd_state ?
-					  connector_status_connected :
-					  connector_status_disconnected);
+		drm_aux_hpd_bridge_notify_extra(&port->bridge->dev,
+						port->hpd_state ?
+						connector_status_connected :
+						connector_status_disconnected,
+						port->hpd_irq ?
+						DRM_CONNECTOR_DP_IRQ_HPD :
+						DRM_CONNECTOR_NO_EXTRA_STATUS);
 
 	gaokun_ec_ucsi_pan_ack(uec->ec, port->idx);
 }

-- 
2.47.3

Re: [PATCH v4 4/8] drm/bridge: pass extra events to the HPD callback

[Francesco Dolcini]

On Mon, Jun 08, 2026 at 12:33:05AM +0300, Dmitry Baryshkov wrote:
> The DisplayPort standard defines a special kind of HPD events called
> IRQ_HPD. These events are used to notify DP Source about the events on
> the Sink side.
> 
> Bridge drivers report these events through the
> drm_bridge_hpd_notify_extra(). Pass down the extra status to the HPD
> callback, specified during the drm_bridge_hpd_enable(), letting
> underlying drivers (e.g. drm_bridge_connector) to receive these events.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

Acked-by: Francesco Dolcini <francesco.dolcini@toradex.com> # lt8912b