From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender4-op-o11.zoho.com (sender4-op-o11.zoho.com [136.143.188.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F110A42C4ED for ; Fri, 31 Jul 2026 14:22:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.11 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785507779; cv=pass; b=hoHph/1Eaxsn09yI34m4NyVFqT32xymo5+Z9OYHDYVS84z/GA7/sdEU1OcVjwKN+BgDO2AvSl4NC00tFdOMuke0/XElM1vplb0UsCCZw2kAXx060o+vD8AXRxSATwDOmxxivSZpki6Om8dwRQ0alRGwuSbjfC+SDCAcUCLD/5d0= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785507779; c=relaxed/simple; bh=jdOwC3ogTiDPjovVks4J46w9EwO3Me9uSxW8NhIRVSM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TbNuq00YbyfcywQNlvwK6E5RiRn67ONd1sfy7I33jXa3TSXHUUfZlZHxG9n76D2NTaaUsmrjeD58OQPqMVsrk7A76PigIB5WQ+OkhnJRSMZGCRuavVHF/xldJTZ0OfeFa9CE+LHJ2iaqvRshz5DXJk7OaFhgY2k/VS3PQZpTlzg= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (1024-bit key) header.d=collabora.com header.i=sebastian.reichel@collabora.com header.b=QrZir8gD; arc=pass smtp.client-ip=136.143.188.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=collabora.com header.i=sebastian.reichel@collabora.com header.b="QrZir8gD" ARC-Seal: i=1; a=rsa-sha256; t=1785507608; cv=none; d=zohomail.com; s=zohoarc; b=gonwM0okZ6hITbCN/Ts7G4RSWCX89laF+zumSUVrwAm3oSEImua8/Ip3XZcGnxGl6XULlPKir3oD+3KhbSjsBbHJmflovKlVNIet0TDQsXb8fx/h/+dT+UySSYxxy8WmZuNHv7rmBoz54JNsjmDndkN0KzNKJRvCiAzgsmnR6L0= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1785507608; h=Content-Type:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:Subject:Subject:To:To:Message-Id:Reply-To; bh=GgkkzLgavD1JLOx9pOWVhcYj+T5mcWCBWQkfA5oQhms=; b=GO84OCE01uj9mMMoC8z/5OXltmEtqpXuHswEdTAQV34Pwa6FrxD8eUBTRduk0R2XrpptLJMj1k37Vv17SECccV8EYkX0jKqBt474eRpYtZiLi7vqIIJ8h7pkAcWX6adfFINnaHCzLHTTNRqrU2sOpFsade18MPzbvyu+6ec57Bg= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=sebastian.reichel@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1785507608; s=zohomail; d=collabora.com; i=sebastian.reichel@collabora.com; h=Date:Date:From:From:To:To:Cc:Cc:Subject:Subject:Message-ID:MIME-Version:Content-Type:In-Reply-To:Message-Id:Reply-To; bh=GgkkzLgavD1JLOx9pOWVhcYj+T5mcWCBWQkfA5oQhms=; b=QrZir8gD1Fhl9tzI/e8fj0GnAtfLqy68zI9Af7VVWI+IfKh65fPf+imDzAqgKqPD wUDfyPTDepxJe5R4FEnzDMOw676FlFfi2td6hv0a8mj7wfEnofA0ik73cXA2DAn2ojj zzFcZ+pxpDWEmGy+u/SUGIL66JCeHlrmrXRkBV0w= Received: by mx.zohomail.com with SMTPS id 1785507607193239.6197346559776; Fri, 31 Jul 2026 07:20:07 -0700 (PDT) Received: by venus (Postfix, from userid 1000) id A7E0118029A; Fri, 31 Jul 2026 16:20:00 +0200 (CEST) Date: Fri, 31 Jul 2026 16:20:00 +0200 From: Sebastian Reichel To: Chaoyi Chen Cc: Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Sandy Huang , Heiko =?utf-8?Q?St=C3=BCbner?= , Andy Yan , Vinod Koul , Chaoyi Chen , Nicolas Frattaroli , Heikki Krogerus , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-phy@lists.infradead.org Subject: Re: [PATCH v5 1/6] drm/bridge: Implement generic USB Type-C DP HPD bridge Message-ID: References: <20260730013349.51-1-kernel@airkyi.com> <20260730013349.51-2-kernel@airkyi.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="mc36q3ts5ojyt2ub" Content-Disposition: inline In-Reply-To: <20260730013349.51-2-kernel@airkyi.com> X-Zoho-Virus-Status: 1 X-Zoho-AV-Stamp: zmail-av-0.2.10.1.5.2/285.486.37 X-ZohoMailClient: External --mc36q3ts5ojyt2ub Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH v5 1/6] drm/bridge: Implement generic USB Type-C DP HPD bridge MIME-Version: 1.0 Hi, On Thu, Jul 30, 2026 at 09:33:44AM +0800, Chaoyi Chen wrote: > From: Chaoyi Chen >=20 > 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. >=20 > To describe the relationship between the DP controller and the Type-C > port device, we usually using drm_bridge to build a bridge chain. >=20 > 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. >=20 > 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. >=20 > 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. >=20 > Signed-off-by: Chaoyi Chen > Reviewed-by: Heikki Krogerus > Reviewed-by: Nicolas Frattaroli > --- >=20 > (no changes since v5) >=20 > Changes in v4: > - Scan the entire typec_bus and attempt to register the hpd bridge, > so as not to miss devices that were already added during initialization. >=20 > (no changes since v3) >=20 > Changes in v2: > - Add copyright text. > - Remove useless goto. > --- > drivers/gpu/drm/bridge/Kconfig | 10 +++ > drivers/gpu/drm/bridge/Makefile | 1 + > .../gpu/drm/bridge/aux-hpd-typec-dp-bridge.c | 64 +++++++++++++++++++ > 3 files changed, 75 insertions(+) > create mode 100644 drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c >=20 > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kcon= fig > index 4a57d49b4c6d..9739b2a19758 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. > =20 > +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 > =20 > diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Mak= efile > index 15cc821d85b7..d88a9e1ccc9a 100644 > --- a/drivers/gpu/drm/bridge/Makefile > +++ b/drivers/gpu/drm/bridge/Makefile > @@ -1,6 +1,7 @@ > # SPDX-License-Identifier: GPL-2.0 > obj-$(CONFIG_DRM_AUX_BRIDGE) +=3D aux-bridge.o > obj-$(CONFIG_DRM_AUX_HPD_BRIDGE) +=3D aux-hpd-bridge.o > +obj-$(CONFIG_DRM_AUX_HPD_TYPEC_BRIDGE) +=3D aux-hpd-typec-dp-bridge.o > obj-$(CONFIG_DRM_CHIPONE_ICN6211) +=3D chipone-icn6211.o > obj-$(CONFIG_DRM_CHRONTEL_CH7033) +=3D chrontel-ch7033.o > obj-$(CONFIG_DRM_CROS_EC_ANX7688) +=3D cros-ec-anx7688.o > diff --git a/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c b/drivers/g= pu/drm/bridge/aux-hpd-typec-dp-bridge.c > new file mode 100644 > index 000000000000..43af3ea20f20 > --- /dev/null > +++ b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c > @@ -0,0 +1,64 @@ > +// SPDX-License-Identifier: GPL-2.0+ > +/* > + * Copyright (C) 2026 Rockchip Electronics Co., Ltd. > + * > + * Author: Chaoyi Chen > + */ > +#include > +#include > +#include > + > +#include > + > +static int drm_typec_bus_event(struct notifier_block *nb, > + unsigned long action, void *data) > +{ > + struct device *dev =3D (struct device *)data; > + struct typec_altmode *alt =3D to_typec_altmode(dev); > + > + if (action !=3D BUS_NOTIFY_ADD_DEVICE) > + return NOTIFY_OK; > + > + /* > + * alt->dev.parent->parent : USB-C controller device > + * alt->dev.parent : USB-C connector device > + */ > + if (is_typec_port_altmode(&alt->dev) && alt->svid =3D=3D USB_TYPEC_DP_S= ID) > + drm_dp_hpd_bridge_register(alt->dev.parent->parent, > + to_of_node(alt->dev.parent->fwnode)); So there are 3 ways to end up with duplicated hpd bridges now: 1. TypeC controller driver already registered one manually 2. There is a race in drm_aux_hpd_typec_dp_bridge_module_init, if a device appears between registering the notifier and looping through all pre-existing devices 3. Reloading the aux-hpd-typec-dp-bridge module re-registers the bridges It's not a huge problem as the system works with the duplicated HPD bridges, but it's also quite ugly. I think it can be trivially avoided by adding this function to drivers/gpu/drm/bridge/aux-hpd-bridge.c and then making use of it here as an additional check (code untested): bool drm_device_has_dp_hpd_bridge(struct device *parent) { struct device *hpd_bridge =3D device_find_child_by_name(parent, "dp_hpd_br= idge"); if (!hpd_bridge) return false; put_device(hpd_bridge); return true; } EXPORT_SYMBOL_GPL(drm_dev_has_dp_hpd_bridge); That would solve all of the above, but leaves one problem when this module races against manual device creation in a TypeC controller driver. That could be avoided by doing the check in devm_drm_dp_hpd_bridge_alloc() under a lock, but that's probably not worth the trouble (it would require updating all users to handle a new error code like -EEXIST) considering manual registration can be removed from all drivers anyways. Greetings, -- Sebastian > + > + return NOTIFY_OK; > +} > + > +static struct notifier_block drm_typec_event_nb =3D { > + .notifier_call =3D drm_typec_bus_event, > +}; > + > +static int check_device_already_added(struct device *dev, void *data) > +{ > + drm_typec_bus_event(NULL, BUS_NOTIFY_ADD_DEVICE, dev); > + return 0; > +} > + > +static void drm_aux_hpd_typec_dp_bridge_module_exit(void) > +{ > + bus_unregister_notifier(&typec_bus, &drm_typec_event_nb); > +} > + > +static int __init drm_aux_hpd_typec_dp_bridge_module_init(void) > +{ > + bus_register_notifier(&typec_bus, &drm_typec_event_nb); > + /* > + * Before module initialization, some devices may have already been add= ed. > + * Register the HPD bridge for these devices. > + */ > + bus_for_each_dev(&typec_bus, NULL, NULL, check_device_already_added); > + return 0; > +} > + > +module_init(drm_aux_hpd_typec_dp_bridge_module_init); > +module_exit(drm_aux_hpd_typec_dp_bridge_module_exit); > + > +MODULE_AUTHOR("Chaoyi Chen "); > +MODULE_DESCRIPTION("DRM TYPEC DP HPD BRIDGE"); > +MODULE_LICENSE("GPL"); > --=20 > 2.53.0 >=20 --mc36q3ts5ojyt2ub Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEE72YNB0Y/i3JqeVQT2O7X88g7+poFAmpsrwkACgkQ2O7X88g7 +poJkw/+KMpk0PnZBYCg+0tfUFBXNrjPd5jqvIzb1eMIcgN/E1jW9Qt79O6yXAAZ uwdcsGKpQ+DG8mmWZwirFCeeNCXP+GWntMKVkNY4SkLJQWNNha+B/KKuP1sobfP9 c/Td1GfZSMJPG01KtOHpc3lL2R05nJp0v1fZOBPT8TjnH+4E+0XZDgaMtDZataDA p8lEUIOy9ZdVIV3yKRHesuGazKtSTxbNxaX23zqoTPipnuuJtqEP/DC/Z4NUIy5f yZhCNyNH9r8T6xXjhS3Wrg5A7bqz2x5X2UhEnLtKfVYpCo0TZh1vXgkSbQ9Sx8ff n7GQaeDiqZbo87sgCSRtbdXD1TBYgFHoY86qg0cZx2acwEe8mnxYpxV04ScAK4ef IsPhu/IlqZ21S0BRJfYLzDxWGofxDNOiB5CSrFwtpk6g4YHpfIbavMgRQNVqeQ92 s6AiBvA4ot9fqtQTP9dZrT990c8qaluDVZKRoJgdG1nSfVjjZSlsennQi/EpS8yY cL41RQQdNNt1edxs/O/L0KcNrgPojwdx9NwydaO5iKEcGnqQRBg47+lrGFRlcnX3 43HEL5S+F+qcO2cGp7W7B6oFpfSNGxjkMYjIuKmnI+rSCzfodseNcfhEqJLdGbOM DxRmSgCpGAlXirP95hduaKSR2UJ1PwvNUYCfR5LAh5mCApd7VuM= =DFla -----END PGP SIGNATURE----- --mc36q3ts5ojyt2ub--