linux-kernel - [PATCH v5 1/8] usb: typec: Add default HPD device when register DisplayPort altmode

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Message-Id: <20251011033233.97-2-kernel@airkyi.com>
Date: Sat, 11 Oct 2025 11:32:26 +0800
From: Chaoyi Chen <kernel@...kyi.com>
To: Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Sandy Huang <hjc@...k-chips.com>,
	Andy Yan <andy.yan@...k-chips.com>,
	Yubing Zhang <yubing.zhang@...k-chips.com>,
	Frank Wang <frank.wang@...k-chips.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Amit Sunil Dhamne <amitsd@...gle.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Chaoyi Chen <chaoyi.chen@...k-chips.com>,
	Dragan Simic <dsimic@...jaro.org>,
	Johan Jonker <jbx6244@...il.com>,
	Diederik de Haas <didi.debian@...ow.org>,
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
	Peter Robinson <pbrobinson@...il.com>
Cc: linux-usb@...r.kernel.org,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-phy@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org,
	dri-devel@...ts.freedesktop.org
Subject: [PATCH v5 1/8] usb: typec: Add default HPD device when register DisplayPort altmode

From: Chaoyi Chen <chaoyi.chen@...k-chips.com>

Add default DRM AUX HPD bridge device when register DisplayPort
altmode. That makes it redundant for each Type-C driver to implement
a similar registration process in embedded scenarios.

Signed-off-by: Chaoyi Chen <chaoyi.chen@...k-chips.com>
---

Changes in v5:
- Remove the calls related to `drm_aux_hpd_bridge_notify()`.
- Place the helper functions in the same compilation unit.
- Add more comments about parent device.

 drivers/usb/typec/class.c         | 26 ++++++++++++++++++++++++++
 include/linux/usb/typec_altmode.h |  2 ++
 2 files changed, 28 insertions(+)

diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
index 67a533e35150..e9d7772d1a8f 100644
--- a/drivers/usb/typec/class.c
+++ b/drivers/usb/typec/class.c
@@ -8,14 +8,18 @@
 
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/of.h>
 #include <linux/property.h>
 #include <linux/slab.h>
 #include <linux/string_choices.h>
 #include <linux/usb/pd_vdo.h>
+#include <linux/usb/typec_dp.h>
 #include <linux/usb/typec_mux.h>
 #include <linux/usb/typec_retimer.h>
 #include <linux/usb.h>
 
+#include <drm/bridge/aux-bridge.h>
+
 #include "bus.h"
 #include "class.h"
 #include "pd.h"
@@ -538,6 +542,21 @@ const struct device_type typec_altmode_dev_type = {
 	.release = typec_altmode_release,
 };
 
+static void dp_altmode_hpd_device_register(struct typec_altmode *alt)
+{
+	if (alt->svid != USB_TYPEC_DP_SID)
+		return;
+
+	/*
+	 * alt->dev.parent->parent : USB-C controller device
+	 * alt->dev.parent         : USB-C connector device
+	 */
+	alt->hpd_dev = drm_dp_hpd_bridge_register(alt->dev.parent->parent,
+						  to_of_node(alt->dev.parent->fwnode));
+	if (IS_ERR(alt->hpd_dev))
+		alt->hpd_dev = NULL;
+}
+
 static struct typec_altmode *
 typec_register_altmode(struct device *parent,
 		       const struct typec_altmode_desc *desc)
@@ -600,6 +619,13 @@ typec_register_altmode(struct device *parent,
 		return ERR_PTR(ret);
 	}
 
+	/*
+	 * It is too late to register the HPD device when the DisplayPort
+	 * altmode device becomes ready. If the current altmode is DP,
+	 * register a static HPD device.
+	 */
+	dp_altmode_hpd_device_register(&alt->adev);
+
 	return &alt->adev;
 }
 
diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
index b3c0866ea70f..acb0af1b9d5d 100644
--- a/include/linux/usb/typec_altmode.h
+++ b/include/linux/usb/typec_altmode.h
@@ -21,6 +21,7 @@ struct typec_altmode_ops;
  * @desc: Optional human readable description of the mode
  * @ops: Operations vector from the driver
  * @cable_ops: Cable operations vector from the driver.
+ * @hpd_dev: HPD device for DisplayPort
  */
 struct typec_altmode {
 	struct device			dev;
@@ -32,6 +33,7 @@ struct typec_altmode {
 	char				*desc;
 	const struct typec_altmode_ops	*ops;
 	const struct typec_cable_ops	*cable_ops;
+	struct device			*hpd_dev;
 };
 
 #define to_typec_altmode(d) container_of(d, struct typec_altmode, dev)
-- 
2.49.0