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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=1784570401; 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=PI5Oxb9HCfJR7oPD5XfJPeD09VaVWbnvfaj5lOSTQXI=; b=IQqR+m+U/mjAqGizVvFMly5QcjIIaE/3vePjAzA6K22TI7658slUzACY11LrIn7m edZZJ3OOCmrkW+Zp88L8qw86AYN/EMlgxSCqJPV4S33e6eFomYSt6mup8so6MjN0buj rTE1wUvmp1WrV7i93mJ+hhrZCZ2KdghDyrbpcswM= Received: by mx.zohomail.com with SMTPS id 1784570399288490.3932171563042; Mon, 20 Jul 2026 10:59:59 -0700 (PDT) Received: by venus (Postfix, from userid 1000) id 26FF41809C8; Mon, 20 Jul 2026 19:59:53 +0200 (CEST) Date: Mon, 20 Jul 2026 19:59:53 +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 , 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 v3 1/5] drm/bridge: Implement generic USB Type-C DP HPD bridge Message-ID: References: <20260717072323.96-1-kernel@airkyi.com> <20260717072323.96-2-kernel@airkyi.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="qn43nqqaph5qazm4" Content-Disposition: inline In-Reply-To: X-Zoho-Virus-Status: 1 X-Zoho-AV-Stamp: zmail-av-0.2.10.1.5.2/284.544.97 X-ZohoMailClient: External X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260720_110059_889660_F84CF393 X-CRM114-Status: GOOD ( 28.61 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --qn43nqqaph5qazm4 Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH v3 1/5] drm/bridge: Implement generic USB Type-C DP HPD bridge MIME-Version: 1.0 Hi, On Fri, Jul 17, 2026 at 07:19:29PM +0200, Sebastian Reichel wrote: > On Fri, Jul 17, 2026 at 03:23:19PM +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 > Reviewed-by: Sebastian Reichel > Tested-by: Sebastian Reichel # ArmSom S= ige5 >=20 > I gave this a test together with the RK3588/RK3576 USB-C DP AltMode > patches I'm working on. As the fusb302 does a manual registration > for the DRM bridge in its probe function, the bridge is registered > twice: >=20 > root@sige5 # cat /sys/kernel/debug/dri/bridges > ... > bridge[1]: drm_aux_hpd_bridge_funcs > refcount: 4 > type: [10] DP > OF: /soc/i2c@2ac50000/typec-portc@22/connector:usb-c-connector > ops: [0x4] hpd > bridge[2]: drm_aux_hpd_bridge_funcs > refcount: 2 > type: [10] DP > OF: /soc/i2c@2ac50000/typec-portc@22/connector:usb-c-connector > ops: [0x4] hpd > ... >=20 > Apparently the USB-C DP AltMode keeps working, so this just wastes > a few CPU cycles and some memory. So this can land and then we can > remove the manual code from the driver as a follow-up step. I also > gave that a try and things keep working. I won't send the fusb302 > patch for now to ensure its not applied before this patch lands. The above test was done with a kernel having all config options built-in (i.e. no modules). Using arm64 defconfig one ends up with CONFIG_DRM_AUX_HPD_TYPEC_BRIDGE=3Dm But the resulting 'aux-hpd-typec-dp-bridge' module is not loaded automatically resulting in missing bridge registration. Running 'modprobe aux-hpd-typec-dp-bridge' manually in the booted system does not work either as the TypeC controller has already been registered and no new BUS_NOTIFY_ADD_DEVICE is generated. Greetings, -- Sebastian --qn43nqqaph5qazm4 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEE72YNB0Y/i3JqeVQT2O7X88g7+poFAmpeYgsACgkQ2O7X88g7 +pp+TQ//dO/L/gdv3kllo402Dewki5Weq5We6e9xzWhRnm2HCSo/GBdqWFfuxZhw lQJeUcgDS7NJw/Btt1+oseitVUxklDA9U5tdh21nLt6lZ8xybUI4ejCM++GOgCbv rd4Qm9QEsWBL5dSSL7REXU4QqoZMDf7SDO/JMWRyxki0WT4E1HFD1Rq0q/XWnD0/ zVWg01K10udFR7cMY9o8pAEXdqBvMiOncBGmHgHl/cx87yz7XPSDfhzN5y5bHPIs UEZr8vv6nOrhGkOxMqBXs86AEvdkBlOHl02UA2RU5MSukt2qIFz7IXRDxmcTruvq U9Q5ydGWrXNqOYvtaEgmjV844bmy4RVqRKyJTy/OlDLjLvMbdKbvo4s2v9vc1Q9a JKlWr8NlaGUh6vcH/gPgRZVzWp0XrHez3bDxeHK/8cLhzmhB2s6Q587ToGrUuDSp AryltU/IrpTYhOMdXt+hjIHRwo4fVYbKfMP/6ccgL3cVHwqncrhNSKSsoXgqXpsG XnB8Ptw8j6khSsJYsvz7lknc+CEQnC5Xm/Ltg0o9+Co7pY3Elph1W4dM2wqGM+mA xnYe7MtpRuA2wkMmBieyKremABtImf7OAyM6xY0qFJx925K46MwEbDJS+PMw+8PT lpUfz3PvTPEY0UaKQhXusyDfWCQpftab5PHy+kH7BBVDWY1V0hY= =yeQL -----END PGP SIGNATURE----- --qn43nqqaph5qazm4--