Hi, On Thu, Jul 30, 2026 at 09:33:44AM +0800, Chaoyi Chen wrote: > From: Chaoyi Chen > > The HPD function of Type-C DP is implemented through > drm_connector_oob_hotplug_event(). For embedded DP, it is required > that the DRM connector fwnode corresponds to the Type-C port fwnode. > > To describe the relationship between the DP controller and the Type-C > port device, we usually using drm_bridge to build a bridge chain. > > Now several USB-C controller drivers have already implemented the DP > HPD bridge function provided by aux-hpd-bridge.c, it will build a DP > HPD bridge on USB-C connector port device. > > But this requires the USB-C controller driver to manually register the > HPD bridge. If the driver does not implement this feature, the bridge > will not be create. > > So this patch implements a generic DP HPD bridge based on > aux-hpd-bridge.c. It will monitor Type-C bus events, and when a > Type-C port device containing the DP svid is registered, it will > create an HPD bridge for it without the need for the USB-C controller > driver to implement it. > > Signed-off-by: Chaoyi Chen > Reviewed-by: Heikki Krogerus > Reviewed-by: Nicolas Frattaroli > --- > > (no changes since v5) > > Changes in v4: > - Scan the entire typec_bus and attempt to register the hpd bridge, > so as not to miss devices that were already added during initialization. > > (no changes since v3) > > Changes in v2: > - Add copyright text. > - Remove useless goto. > --- > drivers/gpu/drm/bridge/Kconfig | 10 +++ > drivers/gpu/drm/bridge/Makefile | 1 + > .../gpu/drm/bridge/aux-hpd-typec-dp-bridge.c | 64 +++++++++++++++++++ > 3 files changed, 75 insertions(+) > create mode 100644 drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c > > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig > index 4a57d49b4c6d..9739b2a19758 100644 > --- a/drivers/gpu/drm/bridge/Kconfig > +++ b/drivers/gpu/drm/bridge/Kconfig > @@ -30,6 +30,16 @@ config DRM_AUX_HPD_BRIDGE > Simple bridge that terminates the bridge chain and provides HPD > support. > > +if DRM_AUX_HPD_BRIDGE > +config DRM_AUX_HPD_TYPEC_BRIDGE > + tristate > + depends on TYPEC || !TYPEC > + default TYPEC > + help > + Simple bridge that terminates the bridge chain and provides HPD > + support. It build bridge on each USB-C connector device node. > +endif > + > menu "Display Interface Bridges" > depends on DRM && DRM_BRIDGE > > diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile > index 15cc821d85b7..d88a9e1ccc9a 100644 > --- a/drivers/gpu/drm/bridge/Makefile > +++ b/drivers/gpu/drm/bridge/Makefile > @@ -1,6 +1,7 @@ > # SPDX-License-Identifier: GPL-2.0 > obj-$(CONFIG_DRM_AUX_BRIDGE) += aux-bridge.o > obj-$(CONFIG_DRM_AUX_HPD_BRIDGE) += aux-hpd-bridge.o > +obj-$(CONFIG_DRM_AUX_HPD_TYPEC_BRIDGE) += aux-hpd-typec-dp-bridge.o > obj-$(CONFIG_DRM_CHIPONE_ICN6211) += chipone-icn6211.o > obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o > obj-$(CONFIG_DRM_CROS_EC_ANX7688) += cros-ec-anx7688.o > diff --git a/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c > new file mode 100644 > index 000000000000..43af3ea20f20 > --- /dev/null > +++ b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c > @@ -0,0 +1,64 @@ > +// SPDX-License-Identifier: GPL-2.0+ > +/* > + * Copyright (C) 2026 Rockchip Electronics Co., Ltd. > + * > + * Author: Chaoyi Chen > + */ > +#include > +#include > +#include > + > +#include > + > +static int drm_typec_bus_event(struct notifier_block *nb, > + unsigned long action, void *data) > +{ > + struct device *dev = (struct device *)data; > + struct typec_altmode *alt = to_typec_altmode(dev); > + > + if (action != BUS_NOTIFY_ADD_DEVICE) > + return NOTIFY_OK; > + > + /* > + * alt->dev.parent->parent : USB-C controller device > + * alt->dev.parent : USB-C connector device > + */ > + if (is_typec_port_altmode(&alt->dev) && alt->svid == USB_TYPEC_DP_SID) > + drm_dp_hpd_bridge_register(alt->dev.parent->parent, > + to_of_node(alt->dev.parent->fwnode)); So there are 3 ways to end up with duplicated hpd bridges now: 1. TypeC controller driver already registered one manually 2. There is a race in drm_aux_hpd_typec_dp_bridge_module_init, if a device appears between registering the notifier and looping through all pre-existing devices 3. Reloading the aux-hpd-typec-dp-bridge module re-registers the bridges It's not a huge problem as the system works with the duplicated HPD bridges, but it's also quite ugly. I think it can be trivially avoided by adding this function to drivers/gpu/drm/bridge/aux-hpd-bridge.c and then making use of it here as an additional check (code untested): bool drm_device_has_dp_hpd_bridge(struct device *parent) { struct device *hpd_bridge = device_find_child_by_name(parent, "dp_hpd_bridge"); if (!hpd_bridge) return false; put_device(hpd_bridge); return true; } EXPORT_SYMBOL_GPL(drm_dev_has_dp_hpd_bridge); That would solve all of the above, but leaves one problem when this module races against manual device creation in a TypeC controller driver. That could be avoided by doing the check in devm_drm_dp_hpd_bridge_alloc() under a lock, but that's probably not worth the trouble (it would require updating all users to handle a new error code like -EEXIST) considering manual registration can be removed from all drivers anyways. Greetings, -- Sebastian > + > + return NOTIFY_OK; > +} > + > +static struct notifier_block drm_typec_event_nb = { > + .notifier_call = drm_typec_bus_event, > +}; > + > +static int check_device_already_added(struct device *dev, void *data) > +{ > + drm_typec_bus_event(NULL, BUS_NOTIFY_ADD_DEVICE, dev); > + return 0; > +} > + > +static void drm_aux_hpd_typec_dp_bridge_module_exit(void) > +{ > + bus_unregister_notifier(&typec_bus, &drm_typec_event_nb); > +} > + > +static int __init drm_aux_hpd_typec_dp_bridge_module_init(void) > +{ > + bus_register_notifier(&typec_bus, &drm_typec_event_nb); > + /* > + * Before module initialization, some devices may have already been added. > + * Register the HPD bridge for these devices. > + */ > + bus_for_each_dev(&typec_bus, NULL, NULL, check_device_already_added); > + return 0; > +} > + > +module_init(drm_aux_hpd_typec_dp_bridge_module_init); > +module_exit(drm_aux_hpd_typec_dp_bridge_module_exit); > + > +MODULE_AUTHOR("Chaoyi Chen "); > +MODULE_DESCRIPTION("DRM TYPEC DP HPD BRIDGE"); > +MODULE_LICENSE("GPL"); > -- > 2.53.0 >