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Subject: Re: [PATCH v8 6/8] MIPS: DTS: CI20: Add DT nodes for HDMI setup
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <CAMuHMdWO3yosf5eyTPpydVuT3pwvuw9Q=2BUxq+rxPjE3iSnrw@mail.gmail.com>
Date:   Wed, 24 Nov 2021 17:30:05 +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>,
        Ezequiel Garcia <ezequiel@collabora.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>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        "open list:BROADCOM NVRAM DRIVER" <linux-mips@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        letux-kernel@openphoenux.org, Jonas Karlman <jonas@kwiboo.se>,
        DRI Development <dri-devel@lists.freedesktop.org>
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References: <cover.1637691240.git.hns@goldelico.com>
 <d62023e0872e9b393db736f4a0ecf04b3fc1c91b.1637691240.git.hns@goldelico.com>
 <O0K13R.TIL3JBQ5L8TO1@crapouillou.net>
 <04F0ED7C-3D18-4CCF-8F10-E0A36B0E4F4B@goldelico.com>
 <CAMuHMdWO3yosf5eyTPpydVuT3pwvuw9Q=2BUxq+rxPjE3iSnrw@mail.gmail.com>
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Precedence: bulk

Hi Geert,

> Am 24.11.2021 um 17:21 schrieb Geert Uytterhoeven =
<geert@linux-m68k.org>:
>=20
> Hi Nikolaus,
>=20
> On Wed, Nov 24, 2021 at 5:19 PM H. Nikolaus Schaller =
<hns@goldelico.com> wrote:
>>> Am 23.11.2021 um 21:10 schrieb Paul Cercueil <paul@crapouillou.net>:
>>> Le mar., nov. 23 2021 at 19:13:59 +0100, H. Nikolaus Schaller =
<hns@goldelico.com> a =C3=A9crit :
>>>> +    assigned-clock-rates =3D <48000000>, <0>, <54000000>, <0>, =
<27000000>;
>>>> };
>>>> &tcu {
>>>> @@ -509,6 +534,19 @@ pins_i2c4: i2c4 {
>>>>             bias-disable;
>>>>     };
>>>> +    pins_hdmi_ddc: hdmi_ddc {
>>>> +            function =3D "hdmi-ddc";
>>>> +            groups =3D "hdmi-ddc";
>>>> +            bias-disable;
>>>> +    };
>>>> +
>>>> +    /* switch to PF25 as gpio driving DDC_SDA low */
>>>> +    pins_hdmi_ddc_unwedge: hdmi_ddc {
>>>> +            function =3D "hdmi-ddc";
>>>> +            groups =3D "hdmi-ddc";
>>>> +            bias-disable;
>>>> +    };
>>>=20
>>> Your pins_hdmi_ddc and pins_hdmi_ddc_unwedge are the exact same? You =
could just use the former and pass it to both pinctrl-0 and pinctrl-1.
>>=20
>> This was forgotten to remove. We do not make use of the unwedge =
feature because I could not find out how to use pinctrl to switch this =
to gpio25 and drive it low.
>=20
> Using gpio-hog?

well, AFAIR it activates the gpio permanently and is a propery of the =
gpio controller and not of pinmux.
The driver assumes it can use pinmux state switching to drive the =
DDC_SDA line low on demand.

Since it is unlikely that we need it at all (and we have no test case =
that it works) I think we simply can leave
this driver feature unused unless we get a test case.

BR and thanks,
Nikolaus