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Subject: Re: [PATCH v10 4/8] drm/ingenic: Add dw-hdmi driver for jz4780
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <Yad69aTXcGixXvy3@sirena.org.uk>
Date:   Wed, 1 Dec 2021 14:51:51 +0100
Cc:     Paul Cercueil <paul@crapouillou.net>,
        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>,
        Paul Boddie <paul@boddie.org.uk>, 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,
        Ezequiel Garcia <ezequiel@collabora.com>
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Message-Id: <46070A95-0FA9-43F9-A9A9-52A7B58B88F5@goldelico.com>
References: <cover.1638307601.git.hns@goldelico.com>
 <4daf0c5dbed2c47c97003ab8de0a7dbd2a335dc3.1638307601.git.hns@goldelico.com>
 <LKTF3R.YREPOCHOSMQN2@crapouillou.net> <Yad69aTXcGixXvy3@sirena.org.uk>
To:     Mark Brown <broonie@kernel.org>
Precedence: bulk

Hi,

> Am 01.12.2021 um 14:39 schrieb Mark Brown <broonie@kernel.org>:
>=20
> On Wed, Dec 01, 2021 at 01:02:45PM +0000, Paul Cercueil wrote:
>> Le mar., nov. 30 2021 at 22:26:37 +0100, H. Nikolaus Schaller
>=20
>>> +	regulator =3D devm_regulator_get_optional(&pdev->dev, =
"hdmi-5v");
>>> +	if (IS_ERR(regulator)) {
>>> +		ret =3D PTR_ERR(regulator);
>=20
> Why is this using _optional()?  This should only be done when the =
supply
> can be physically absent

There can be +5V for HDMI but without a regulator that is visible to or =
controllable
by the driver.

So hdmi-5v can be simply missing in DTS in which case the driver does =
not need to
care about. The driver just can't turn it on or off.

> (in which case I'd expect to see special
> handling).

The special case is to not enable/disable the regulator if it does not =
exist
and assume that there is hardware providing it otherwise (the driver =
can't know
that except by using get_optional). This is done by the code below

>>> +	if (IS_ERR(regulator)) {

...

> +	if (!regulator)
> +		return 0;
>=20
> +	ret =3D regulator_enable(regulator);

...

BR and thanks,
Nikolaus