Re: [PATCH v15 1/9] drm/bridge: Implement generic USB Type-C DP HPD bridge

[Xu Yang]

On Wed, Mar 04, 2026 at 05:41:44PM +0800, Chaoyi Chen wrote:
> From: Chaoyi Chen <chaoyi.chen@xxxxxxxxxxxxxx>
> 
> 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 <chaoyi.chen@xxxxxxxxxxxxxx>
> Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> 
> (no changes since v14)
> 
> Changes in v13:
> - Only register drm dp hpd bridge for typec port altmode device.
> 
> (no changes since v12)
> 
> Changes in v11:
> - Switch to using typec bus notifiers.
> 
> (no changes since v10)
> 
> Changes in v9:
> - Remove the exposed DRM_AUX_HPD_BRIDGE option, and select
> DRM_AUX_HPD_TYPEC_BRIDGE when it is available.
> - Add more commit comment about problem background.
> 
> Changes in v8:
> - Merge generic DP HPD bridge into one module.
> ---
> 
>  drivers/gpu/drm/bridge/Kconfig                | 10 ++++
>  drivers/gpu/drm/bridge/Makefile               |  1 +
>  .../gpu/drm/bridge/aux-hpd-typec-dp-bridge.c  | 49 +++++++++++++++++++
>  3 files changed, 60 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 a250afd8d662..559487aa09a9 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
> +

Should CONFIG_TYPEC_DP_ALTMODE select this one? Otherwise, we need to do it
manually.

$ grep -nr --include=Kconfig "select DRM_AUX_HPD_BRIDGE" .
./drivers/soc/qcom/Kconfig:118: select DRM_AUX_HPD_BRIDGE
./drivers/usb/typec/ucsi/Kconfig:88:    select DRM_AUX_HPD_BRIDGE if DRM_BRIDGE && OF
./drivers/usb/typec/ucsi/Kconfig:99:    select DRM_AUX_HPD_BRIDGE if DRM_BRIDGE && OF
./drivers/usb/typec/tcpm/Kconfig:62:    select DRM_AUX_HPD_BRIDGE if DRM_BRIDGE && OF
./drivers/usb/typec/tcpm/Kconfig:85:    select DRM_AUX_HPD_BRIDGE if DRM_BRIDGE && OF

Thanks,
Xu Yang