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Subject: Re: [PATCH v12 7/9] drm/bridge: display-connector: add ddc-en gpio
 support
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <DLAO6R.7AAJRIJFJSDD3@crapouillou.net>
Date:   Wed, 2 Feb 2022 12:45:47 +0100
Cc:     Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Kees Cook <keescook@chromium.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Robert Foss <robert.foss@linaro.org>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Harry Wentland <harry.wentland@amd.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        Maxime Ripard <maxime@cerno.tech>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Paul Boddie <paul@boddie.org.uk>,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
        devicetree@vger.kernel.org, linux-mips@vger.kernel.org,
        linux-kernel@vger.kernel.org, letux-kernel@openphoenux.org,
        Jonas Karlman <jonas@kwiboo.se>,
        dri-devel@lists.freedesktop.org
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Message-Id: <67B24AC4-2E72-4A3C-8CCD-785B00F79CB1@goldelico.com>
References: <cover.1643632014.git.hns@goldelico.com>
 <77a7a1daaf381e1651be38adb62f9af9dd6c8fc5.1643632014.git.hns@goldelico.com>
 <DLAO6R.7AAJRIJFJSDD3@crapouillou.net>
To:     Paul Cercueil <paul@crapouillou.net>
Precedence: bulk

Hi Paul,

> Am 02.02.2022 um 11:32 schrieb Paul Cercueil <paul@crapouillou.net>:
>=20
> Hi Nikolaus,
>=20
> Le lun., janv. 31 2022 at 13:26:53 +0100, H. Nikolaus Schaller =
<hns@goldelico.com> a =C3=A9crit :
>> "hdmi-connector.yaml" bindings defines an optional property
>> "ddc-en-gpios" for a single gpio to enable DDC operation.
>> Usually this controls +5V power on the HDMI connector.
>> This +5V may also be needed for HPD.
>> This was not reflected in code.
>> Now, the driver activates the ddc gpio after probe and
>> deactivates after remove so it is "almost on".
>> But only if this driver is loaded (and not e.g. blacklisted
>> as module).
>> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
>> ---
>> drivers/gpu/drm/bridge/display-connector.c | 17 +++++++++++++++++
>> 1 file changed, 17 insertions(+)
>> diff --git a/drivers/gpu/drm/bridge/display-connector.c =
b/drivers/gpu/drm/bridge/display-connector.c
>> index d24f5b90feabf..555395e301096 100644
>> --- a/drivers/gpu/drm/bridge/display-connector.c
>> +++ b/drivers/gpu/drm/bridge/display-connector.c
>> @@ -24,6 +24,7 @@ struct display_connector {
>> 	int			hpd_irq;
>> 	struct regulator	*dp_pwr;
>> +	struct gpio_desc	*ddc_en;
>> };
>> static inline struct display_connector *
>> @@ -345,6 +346,19 @@ static int display_connector_probe(struct =
platform_device *pdev)
>> 		}
>> 	}
>> +	/* enable DDC */
>> +	if (type =3D=3D DRM_MODE_CONNECTOR_HDMIA) {
>> +		conn->ddc_en =3D devm_gpiod_get_optional(&pdev->dev, =
"ddc-en",
>> +						       GPIOD_OUT_HIGH);
>> +
>> +		if (IS_ERR(conn->ddc_en)) {
>> +			dev_err(&pdev->dev, "Couldn't get ddc-en =
gpio\n");
>> +			return PTR_ERR(conn->ddc_en);
>> +		}
>> +
>> +		gpiod_set_value(conn->ddc_en, 1);
>=20
> You already requested the gpio with the GPIOD_OUT_HIGH flag, so this =
can be removed.

Ah, ok!

>=20
>=20
>> +	}
>> +
>> 	conn->bridge.funcs =3D &display_connector_bridge_funcs;
>> 	conn->bridge.of_node =3D pdev->dev.of_node;
>> @@ -373,6 +387,9 @@ static int display_connector_remove(struct =
platform_device *pdev)
>> {
>> 	struct display_connector *conn =3D platform_get_drvdata(pdev);
>> +	if (conn->ddc_en)
>> +		gpiod_set_value(conn->ddc_en, 0);
>=20
> Note that gpiod_set_value() already does the null-check internally.

Indeed.

> I actually do prefer your solution, so this is fine with me, but =
maintainers may have a different opinion.

I am fine with any of them. Just need to know which one to take (and =
test).

BR,
Nikolaus

>=20
> Cheers,
> -Paul
>=20
>> +
>> 	if (conn->dp_pwr)
>> 		regulator_disable(conn->dp_pwr);
>> --
>> 2.33.0
>=20
>=20