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Tue, 31 Mar 2026 04:09:35 +0200 (CEST) Date: Tue, 31 Mar 2026 04:09:35 +0200 From: Sebastian Reichel To: Chaoyi Chen Cc: Sandy Huang , Heiko =?utf-8?Q?St=C3=BCbner?= , Andy Yan , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Damon Ding , Dmitry Baryshkov , Alexey Charkov , dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, kernel@collabora.com Subject: Re: [PATCH 00/10] Synopsys DisplayPort Controller improvements for Rockchip platforms Message-ID: References: <20260326-synopsys-dw-dp-improvements-v1-0-501849162290@collabora.com> Precedence: bulk X-Mailing-List: devicetree@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="yaujaqtrdlo2vvms" Content-Disposition: inline In-Reply-To: X-Zoho-Virus-Status: 1 X-Zoho-AV-Stamp: zmail-av-0.2.2.1.5.2/274.894.35 X-ZohoMailClient: External --yaujaqtrdlo2vvms Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH 00/10] Synopsys DisplayPort Controller improvements for Rockchip platforms MIME-Version: 1.0 Hi, On Tue, Mar 31, 2026 at 09:18:32AM +0800, Chaoyi Chen wrote: > On 3/30/2026 7:50 PM, Sebastian Reichel wrote: > > On Mon, Mar 30, 2026 at 09:34:15AM +0800, Chaoyi Chen wrote: > >>> There are two parts, which possibly need some discussion: > >>> > >>> 1. I added a dedicated bridge callback for out-of-band hotplug event= s, > >>> which is separate from the hotplug_notify. I have a feeling, that > >>> there might be a better solution, but haven't found it. > >> > >> Could you explain what an out-of-band hotplug event is? > >> > >> Can't the drivers/usb/typec/altmodes/displayport.c respond to these > >> hot-plug events? Thank you. > >=20 > > That is what generates the out-of-band hotplug event in the first > > place via drm_connector_oob_hotplug_event(). The oob in that call > > means out of band. > >=20 > > If you look at that function it calls oob_hotplug_event() callback > > on the DRM connector, which is then implemented by > > drm_bridge_connector_oob_hotplug_event(). This function calls uses > > the normal hpd handling (shared by in-band and out-of-band) and I'm > > patching it, so that the bridges are aware of hpd explicitly being > > provided out-of-band. > >=20 >=20 > Ah, I'm actually more concerned with the specific types of events. > For example, the "explicitly" provided HPD you mentioned here.=20 > Isn't drm_connector_oob_hotplug_event able to provide those? >=20 > I assume you=E2=80=99re looking for an oob event that is propagated along= the > bridge chain, rather than at the connector. Is that so? Thank you. The connector has a dedicated hotplug oob event callback, but I obviously need the event on the bridge, since the DP controller is implemented as bridge. The existing infrastructure propages it down to the bridge chain via drm_bridge_hpd_notify(), which can be received by the DP controller via the .hpd_notify callback in struct drm_bridge_funcs. The problem is, that this receives events for in-band AND out-of-band hotplug events. That's why I added a new bridge callback, which hooks into the existing framework, but only delivers out-of-band events and no in-band events. The problem with receiving in-band in addition to out-of-band is that the out-of-band signal should set the hotplug pin accordingly, but the in-band detection also checks the actual DP link. If the OOB hotplug signal says "nothing plugged", the hotplug pin should be forced off, but if the DP link detection fails, the hotplug pin should not be force disabled, as that makes any further detection tries useless. Greetings, -- Sebastian --yaujaqtrdlo2vvms Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEE72YNB0Y/i3JqeVQT2O7X88g7+poFAmnLLNsACgkQ2O7X88g7 +prmkhAAjDm4M4nMr7eRb8BBJebGTWT4fZ5RCqQUQp2qlPxp2H7ejOzNdsIScKOy Fg4Bkkn3ROZ7G6svVSjkAf/pN3fAZoUJd7LPILYJgemGN9mvQvR1g/WDf+L1aYqR oPTeJkV3v5hcOpkYEPYH2nibSA8RqwUfxxGC2VLo7Sdzx6rFLMpvctM8BH4iZIfa nKdyqVBuu+QHMIwMbdQDngjHYHxFKEtKibzShG3sL/sGwD3kMUX+QliB6PRr0B0O BY3+aIlqWoAxBc1HKanTwYP2Syo6uRUNb1YJwZ7JG8BdQgtxSWhc+wyMMncyZead 4R+2Hdr+egKMcxpd4ISADDtsr1KjeKvA5p5AoXQKZfngCB/glGu+kTH+CG555zAr g/vYXTs4inZfBollzyHgcqVqY/2rcNtHhD1K7I8gq8i7cAeSo5BFe4G+bnpDHE3s kiyOfKokqgCg0Ql++qf4/Vause/0KaOY9e9VauD8FMNDzsiQ19YGihRsI1VSzeG8 UCAVauBMt7xBKSTEVS7PmUtZXa20DuhtQqwIGpGnPXuk72gmdxIDDlUM1Wva9eyt niRqdC6KyOqrf3Dc8U1JhwPb1fxAJ7iLw3xGXIlEaFjd+yqcEVvPhKNJ2iVUNrup GF8lP5Po5r4LXBio3AACey2f1nc6z6jBaSya5T1jmalppj+LnDU= =iO8H -----END PGP SIGNATURE----- --yaujaqtrdlo2vvms--