On Mon, Jun 29, 2026 at 09:29:08AM +0800, Chaoyi Chen wrote:

Hello Xu Yang,

On 6/26/2026 7:15 PM, Xu Yang wrote:

quoted

On Wed, Mar 04, 2026 at 05:41:44PM +0800, Chaoyi Chen wrote:

quoted

From: Chaoyi Chen <redacted>

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 <redacted>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
---

(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

That's a fair point. But based on the previous discussion, Heikki
point out that configurations in the TYPEC subsystem should not
select configurations from DRM.

I have just reviewed your previous patchsets but I did't find such opinion from
Heikki. Otherwise, why are tcpm.c/ucsi.c already allowed to add the above select
condition in their configs?

I think Heikki means that the DRM_AUX_HPD_BRIDGE shouldn't been selected at the
top level of Type-C subsystem. Because not all Type-C devices support the DP function.

As a generic Type-C DP HPD bridge, displayport.c will likely need to use it in
the future. Therefore, allowing displayport.c to select DRM_AUX_HPD_BRIDGE makes sense.

According to my testing, it's impossible to build this driver in unless TYPEC_FUSB302
or a relevant CONFIG is built in to select DRM_AUX_HPD_BRIDGE, or the defconfig is modified.

Thanks,
Xu Yang