On 11/17/2025 4:40 PM, Heikki Krogerus wrote:
Tue, Nov 11, 2025 at 06:50:33PM +0800, Chaoyi Chen kirjoitti:
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]>
Normally there is no "help" section for hidden config options. I
guess it can not cause any harm? It is a bit confusing, though. But
FWIW:
The hidden options "DRM_AUX_BRIDGE" and "DRM_AUX_HPD_BRIDGE" also have a help
section.
I think this is just for comment purposes :)
Reviewed-by: Heikki Krogerus <[email protected]>
---
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 | 50 +++++++++++++++++++
3 files changed, 61 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
+
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..a3a0393d2e72 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..9cb6a0cb0f0a
--- /dev/null
+++ b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0+
+#include <linux/of.h>
+#include <linux/usb/typec_altmode.h>
+#include <linux/usb/typec_dp.h>
+
+#include <drm/bridge/aux-bridge.h>
+
+static int drm_typec_bus_event(struct notifier_block *nb,
+ unsigned long action, void *data)
+{
+ struct typec_altmode *alt = (struct typec_altmode *)data;
+
+ if (action != TYPEC_ALTMODE_REGISTERED)
+ goto done;
+
+ if (is_typec_partner(&alt->dev) || alt->svid != USB_TYPEC_DP_SID)
+ goto done;
+
+ /*
+ * alt->dev.parent->parent : USB-C controller device
+ * alt->dev.parent : USB-C connector device
+ */
+ drm_dp_hpd_bridge_register(alt->dev.parent->parent,
+ to_of_node(alt->dev.parent->fwnode));
+
+done:
+ return NOTIFY_OK;
+}
+
+static struct notifier_block drm_typec_event_nb = {
+ .notifier_call = drm_typec_bus_event,
+};
+
+static void drm_aux_hpd_typec_dp_bridge_module_exit(void)
+{
+ typec_altmode_unregister_notify(&drm_typec_event_nb);
+}
+
+static int __init drm_aux_hpd_typec_dp_bridge_module_init(void)
+{
+ typec_altmode_register_notify(&drm_typec_event_nb);
+
+ return 0;
+}
+
+module_init(drm_aux_hpd_typec_dp_bridge_module_init);
+module_exit(drm_aux_hpd_typec_dp_bridge_module_exit);
+
+MODULE_DESCRIPTION("DRM TYPEC DP HPD BRIDGE");
+MODULE_LICENSE("GPL");
--
2.51.1
--
Best,
Chaoyi
