Hi, On Fri, Jul 17, 2026 at 07:19:29PM +0200, Sebastian Reichel wrote: > On Fri, Jul 17, 2026 at 03:23:19PM +0800, Chaoyi Chen wrote: > > From: Chaoyi Chen <[email protected]> > > > > 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 <[email protected]> > > Reviewed-by: Heikki Krogerus <[email protected]> > > Reviewed-by: Nicolas Frattaroli <[email protected]> > > --- > > Reviewed-by: Sebastian Reichel <[email protected]> > Tested-by: Sebastian Reichel <[email protected]> # ArmSom Sige5 > > I gave this a test together with the RK3588/RK3576 USB-C DP AltMode > patches I'm working on. As the fusb302 does a manual registration > for the DRM bridge in its probe function, the bridge is registered > twice: > > root@sige5 # cat /sys/kernel/debug/dri/bridges > ... > bridge[1]: drm_aux_hpd_bridge_funcs > refcount: 4 > type: [10] DP > OF: /soc/i2c@2ac50000/typec-portc@22/connector:usb-c-connector > ops: [0x4] hpd > bridge[2]: drm_aux_hpd_bridge_funcs > refcount: 2 > type: [10] DP > OF: /soc/i2c@2ac50000/typec-portc@22/connector:usb-c-connector > ops: [0x4] hpd > ... > > Apparently the USB-C DP AltMode keeps working, so this just wastes > a few CPU cycles and some memory. So this can land and then we can > remove the manual code from the driver as a follow-up step. I also > gave that a try and things keep working. I won't send the fusb302 > patch for now to ensure its not applied before this patch lands.
The above test was done with a kernel having all config options built-in (i.e. no modules). Using arm64 defconfig one ends up with CONFIG_DRM_AUX_HPD_TYPEC_BRIDGE=m But the resulting 'aux-hpd-typec-dp-bridge' module is not loaded automatically resulting in missing bridge registration. Running 'modprobe aux-hpd-typec-dp-bridge' manually in the booted system does not work either as the TypeC controller has already been registered and no new BUS_NOTIFY_ADD_DEVICE is generated. Greetings, -- Sebastian
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