linux-kernel - Re: [PATCH v12 7/9] drm/bridge: display-connector: add ddc-en gpio support

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Date:   Wed, 2 Feb 2022 12:45:47 +0100
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Kees Cook <keescook@...omium.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Harry Wentland <harry.wentland@....com>,
        Sam Ravnborg <sam@...nborg.org>,
        Maxime Ripard <maxime@...no.tech>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Paul Boddie <paul@...die.org.uk>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        devicetree@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org, letux-kernel@...nphoenux.org,
        Jonas Karlman <jonas@...boo.se>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v12 7/9] drm/bridge: display-connector: add ddc-en gpio
 support

Hi Paul,

> Am 02.02.2022 um 11:32 schrieb Paul Cercueil <paul@...pouillou.net>:
> 
> Hi Nikolaus,
> 
> Le lun., janv. 31 2022 at 13:26:53 +0100, H. Nikolaus Schaller <hns@...delico.com> a écrit :
>> "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@...delico.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 == DRM_MODE_CONNECTOR_HDMIA) {
>> +		conn->ddc_en = 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);
> 
> You already requested the gpio with the GPIOD_OUT_HIGH flag, so this can be removed.

Ah, ok!

> 
> 
>> +	}
>> +
>> 	conn->bridge.funcs = &display_connector_bridge_funcs;
>> 	conn->bridge.of_node = pdev->dev.of_node;
>> @@ -373,6 +387,9 @@ static int display_connector_remove(struct platform_device *pdev)
>> {
>> 	struct display_connector *conn = platform_get_drvdata(pdev);
>> +	if (conn->ddc_en)
>> +		gpiod_set_value(conn->ddc_en, 0);
> 
> 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

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