[PATCH v8 03/10] drm/bridge: Implement generic USB Type-C DP HPD bridge
Chaoyi Chen
chaoyi.chen at rock-chips.com
Mon Nov 3 17:18:33 PST 2025
On 11/3/2025 9:48 PM, Heikki Krogerus wrote:
>>>> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
>>>> index a250afd8d662..17257b223a28 100644
>>>> --- a/drivers/gpu/drm/bridge/Kconfig
>>>> +++ b/drivers/gpu/drm/bridge/Kconfig
>>>> @@ -23,13 +23,16 @@ config DRM_AUX_BRIDGE
>>>> build bridges chain.
>>>> config DRM_AUX_HPD_BRIDGE
>>>> - tristate
>>>> + tristate "AUX HPD bridge support"
>>> Why? No, this is supposed to be selected by other drivers. Users don't
>>> know an wouldn't know what is this.
>> In v7, I implemented an additional module for selecting this option. But
>> Heikki believes that it would be better to merge the two modules into one.
> Like I said before, I was merely curious why not just squash the
> support into that AUX_PD_HPD_BRIDGE. If that does not make sense, then
> so be it - make it a "Display Interface Bridge" driver like you
> originally proposed.
Yes, it is.
>>>> depends on DRM_BRIDGE && OF
>>>> select AUXILIARY_BUS
>>>> help
>>>> Simple bridge that terminates the bridge chain and provides HPD
>>>> support.
>>>> + Specifically, if you want a default Type-C DisplayPort HPD bridge for
>>>> + each port of the Type-C controller, say Y here.
>>>> +
>>>> menu "Display Interface Bridges"
>>>> depends on DRM && DRM_BRIDGE
>>>> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
>>>> index c7dc03182e59..2998937444bc 100644
>>>> --- a/drivers/gpu/drm/bridge/Makefile
>>>> +++ b/drivers/gpu/drm/bridge/Makefile
>>>> @@ -1,6 +1,12 @@
>>>> # SPDX-License-Identifier: GPL-2.0
>>>> obj-$(CONFIG_DRM_AUX_BRIDGE) += aux-bridge.o
>>>> -obj-$(CONFIG_DRM_AUX_HPD_BRIDGE) += aux-hpd-bridge.o
>>>> +
>>>> +hpd-bridge-y := aux-hpd-bridge.o
>>>> +ifneq ($(CONFIG_TYPEC),)
>>>> +hpd-bridge-y += aux-hpd-typec-dp-bridge.o
>>>> +endif
>>>> +obj-$(CONFIG_DRM_AUX_HPD_BRIDGE) += hpd-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-bridge.c b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
>>>> index 2e9c702c7087..11ad6dc776c7 100644
>>>> --- a/drivers/gpu/drm/bridge/aux-hpd-bridge.c
>>>> +++ b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
>>>> @@ -12,6 +12,8 @@
>>>> #include <drm/drm_bridge.h>
>>>> #include <drm/bridge/aux-bridge.h>
>>>> +#include "aux-hpd-bridge.h"
>>>> +
>>>> static DEFINE_IDA(drm_aux_hpd_bridge_ida);
>>>> struct drm_aux_hpd_bridge_data {
>>>> @@ -204,7 +206,26 @@ static struct auxiliary_driver drm_aux_hpd_bridge_drv = {
>>>> .id_table = drm_aux_hpd_bridge_table,
>>>> .probe = drm_aux_hpd_bridge_probe,
>>>> };
>>>> -module_auxiliary_driver(drm_aux_hpd_bridge_drv);
>>>> +
>>>> +static int drm_aux_hpd_bridge_mod_init(void)
>>>> +{
>>>> + int ret;
>>>> +
>>>> + ret = auxiliary_driver_register(&drm_aux_hpd_bridge_drv);
>>>> + if (ret)
>>>> + return ret;
>>>> +
>>>> + return drm_aux_hpd_typec_dp_bridge_init();
>>>> +}
>>>> +
>>>> +static void drm_aux_hpd_bridge_mod_exit(void)
>>>> +{
>>>> + drm_aux_hpd_typec_dp_bridge_exit();
>>>> + auxiliary_driver_unregister(&drm_aux_hpd_bridge_drv);
>>>> +}
>>>> +
>>>> +module_init(drm_aux_hpd_bridge_mod_init);
>>>> +module_exit(drm_aux_hpd_bridge_mod_exit);
>>>> MODULE_AUTHOR("Dmitry Baryshkov <dmitry.baryshkov at linaro.org>");
>>>> MODULE_DESCRIPTION("DRM HPD bridge");
>>>> diff --git a/drivers/gpu/drm/bridge/aux-hpd-bridge.h b/drivers/gpu/drm/bridge/aux-hpd-bridge.h
>>>> new file mode 100644
>>>> index 000000000000..69364731c2f1
>>>> --- /dev/null
>>>> +++ b/drivers/gpu/drm/bridge/aux-hpd-bridge.h
>>>> @@ -0,0 +1,13 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0-only */
>>>> +#ifndef AUX_HPD_BRIDGE_H
>>>> +#define AUX_HPD_BRIDGE_H
>>>> +
>>>> +#if IS_REACHABLE(CONFIG_TYPEC)
>>>> +int drm_aux_hpd_typec_dp_bridge_init(void);
>>>> +void drm_aux_hpd_typec_dp_bridge_exit(void);
>>>> +#else
>>>> +static inline int drm_aux_hpd_typec_dp_bridge_init(void) { return 0; }
>>>> +static inline void drm_aux_hpd_typec_dp_bridge_exit(void) { }
>>>> +#endif /* IS_REACHABLE(CONFIG_TYPEC) */
>>>> +
>>>> +#endif /* AUX_HPD_BRIDGE_H */
>>>> 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..6f2a1fca0fc5
>>>> --- /dev/null
>>>> +++ b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c
>>>> @@ -0,0 +1,47 @@
>>>> +// SPDX-License-Identifier: GPL-2.0+
>>>> +#include <linux/of.h>
>>>> +#include <linux/usb/typec_altmode.h>
>>>> +#include <linux/usb/typec_dp.h>
>>>> +#include <linux/usb/typec_notify.h>
>>>> +
>>>> +#include <drm/bridge/aux-bridge.h>
>>>> +
>>>> +#include "aux-hpd-bridge.h"
>>>> +
>>>> +#if IS_REACHABLE(CONFIG_TYPEC)
>>>> +static int drm_typec_bus_event(struct notifier_block *nb,
>>>> + unsigned long action, void *data)
>>>> +{
>>> This feels like this should be a part of the Type-C subsystem rather
>>> than DRM.
>> In v7, this used to be a part of the Type-C subsystem. I'm not sure what
>> Heikki thinks about this.
> Your original proposal of making the entire TYPEC subsystem depend on
> DRM is _not_ going to happen. In general, if I've now understood this
> correctly, this thing probable should be a "display interface bridge
> driver", similar to what you proposed in the previous version.
>
> Note also that you could make it selected automatically, so there is
> no need for user selectable option if that's the preference. Kconfig
> and Makefile gives you options on how to do that. For example, maybe
> this Kconfig works (or does not, but something like it will):
>
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index a250afd8d662..7487024ba2ce 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -30,6 +30,15 @@ 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
> +
> +endif /* DRM_AUX_HPD_BRIDGE */
> +
> menu "Display Interface Bridges"
> depends on DRM && DRM_BRIDGE
Thank you for your code. I think both of your points make sense. So choosing the approach you mentioned now (similar to v7) might be a reasonable compromise.
>
>
>
> thanks,
>
--
Best,
Chaoyi
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