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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: <CAMuHMdV5sjVg6BEm3zgvvsJDHJwKP1A8rh-sama8suCG5SYQyA@mail.gmail.com>
Date:   Thu, 25 Nov 2021 09:29:02 +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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To:     Geert Uytterhoeven <geert@linux-m68k.org>
Precedence: bulk

Hi Gert,

> Am 25.11.2021 um 08:58 schrieb Geert Uytterhoeven =
<geert@linux-m68k.org>:
>=20
> Hi Nikolaus,
>=20
> On Wed, Nov 24, 2021 at 5:31 PM H. Nikolaus Schaller =
<hns@goldelico.com> wrote:
>>> Am 24.11.2021 um 17:21 schrieb Geert Uytterhoeven =
<geert@linux-m68k.org>:
>>> 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?
>>=20
>> well, AFAIR it activates the gpio permanently and is a propery of the =
gpio controller and not of pinmux.
>=20
> Yes, hogs are permanently (ignoring DT overlay tricks).
>=20
>> The driver assumes it can use pinmux state switching to drive the =
DDC_SDA line low on demand.
>=20
> Add an optional wedge-gpios property for switching?

That would touch the synopsys driver core and does not appear to be =
required for jz4780 operation.
We just add a separate driver specialisation for some parameters and set =
up the device tree.

So it is beyond the scope of our work (neither needed, nor can we test =
it).
If you want to add that, please go ahead.

BR and thanks,
Nikolaus