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Subject: Re: [RFC PATCH v3 4/7] drm/panel: nv3052c: Add Fascontek FS035VG158
 LCD display
From:   Paul Cercueil <paul@crapouillou.net>
To:     John Watts <contact@jookia.org>
Cc:     dri-devel@lists.freedesktop.org,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Jessica Zhang <quic_jesszhan@quicinc.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Shawn Guo <shawnguo@kernel.org>,
        Heiko Stuebner <heiko@sntech.de>,
        Chris Morgan <macromorgan@hotmail.com>,
        Jagan Teki <jagan@edgeble.ai>,
        Christophe Branchereau <cbranchereau@gmail.com>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Mon, 25 Sep 2023 11:43:26 +0200
In-Reply-To: <ZRFRFXCKTIb9x7GW@titan>
References: <20230925021059.451019-1-contact@jookia.org>
         <20230925021059.451019-5-contact@jookia.org>
         <ebd5808fe3029e46376aea3c25d3770a6b406fdc.camel@crapouillou.net>
         <ZRFRFXCKTIb9x7GW@titan>
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Le lundi 25 septembre 2023 =C3=A0 19:21 +1000, John Watts a =C3=A9crit=C2=
=A0:
> On Mon, Sep 25, 2023 at 11:12:29AM +0200, Paul Cercueil wrote:
> > Hi John,
> >=20
> > Just to be sure, your fascontek panel won't work with the
> > initialization sequence of the leadtek panel?
>=20
> Yes, it does work.

OK, why not use the leadtek's initialization sequence then?

From what I can see, you have a panel with a NV3052C chip, so the
existing initialization sequence should already work.

>=20
> > Did you try with the existing display modes? If you can afford the
> > 24
> > MHz clock (and if it works with your panel) it will give you a
> > perfect
> > 60.0 Hz refresh rate, while this mode above will give you above
> > 59.93
> > Hz (which is not that bad though).
>=20
> No I didn't test with this.
>=20
> In general I don't feel comfortable submitting code that strays from
> what is
> recommended by the manufacturer.

The NV3052C datasheet does not give any settings for a 640x480 panel, I
only see suggested settings for a 720x1280 vertical panel.

Unless you have a min/max range specified, the values you see in there
are only suggestions for a working setup, that doesn't mean they are
the only recommended ones.

Cheers,
-Paul