Re: [PATCH v4 3/3] drm/panel-fannal-c3004: Add fannal c3004 DSI panel

From: Paulo Pavacic <pavacic.p@gmail.com>
To: Marek Vasut <marex@denx.de>
Cc: neil.armstrong@linaro.org, conor+dt@kernel.org,
	krzysztof.kozlowski+dt@linaro.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	robh+dt@kernel.org, Jagan Teki <jagan@amarulasolutions.com>,
	sam@ravnborg.org, Maya Matuszczyk <maccraft123mc@gmail.com>
Subject: Re: [PATCH v4 3/3] drm/panel-fannal-c3004: Add fannal c3004 DSI panel
Date: Fri, 7 Jul 2023 17:26:31 +0200	[thread overview]
Message-ID: <CAO9szn20RY3uBDceyUJ1S+gb=FN8Hd5qqMfOSbitHFyFCZ+iLg@mail.gmail.com> (raw)
In-Reply-To: <0d43e653-32cd-b25e-40fa-6f0571048467@denx.de>

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Hello Marek,

čet, 6. srp 2023. u 17:26 Marek Vasut <marex@denx.de> napisao je:
>
> On 7/6/23 17:18, Paulo Pavacic wrote:
> > Hello Linus,
> >
> > čet, 22. lip 2023. u 10:22 Linus Walleij <linus.walleij@linaro.org> napisao je:
> >>
> >> On Wed, Jun 21, 2023 at 5:09 PM Paulo Pavacic <pavacic.p@gmail.com> wrote:
> >>
> >>> A lot of modifications to st7701 are required. I believe it would
> >>> result in a driver that doesn't look or work the same. e.g compare
> >>> delays between initialization sequences of panel-fannal-c3004 and
> >>> panel-st7701. I think it would be optimal to create st7701s driver and
> >>> have special handling for st7701s panels. If there was a flag for
> >>> whether panel is st7701 or st7701s it would end up looking like a
> >>> mess.
> >>
> >> What matters is if the original authors of the old st7701 driver are
> >> around and reviewing and testing patches at all. What we need is
> >> active maintainers. (Added Jagan, Marek & Maya).
> >>
> >> I buy the reasoning that the st7701s is perhaps substantially different
> >> from st7701.
> >>
> >> If st7701s is very different then I suppose it needs a separate driver,
> >> then all we need to to name the driver properly, i.e.
> >> panel-sitronix-st7701s.c.
> >
> > I had in person talk with Paul Kocialkowski and I have concluded that
> > this is the best solution.
> > I believe I should rename it to st7701s due to the hardware changes. I
> > would like to create V5 patch with driver renamed to st7701s.
> > Please let me know if you agree / disagree.
>
> If I recall it right, the ST7701 and ST7701S are basically the same
> chip, aren't they ?

I'm currently exploring all the differences. There aren't a lot of
differences, but there are some.
So far I can see that default register values are different, new
previously unused registers are now used and there has been some
reordering of how info is placed in registers [1] (data bits are in
different order). Moreover, instructions to some commands have been
changed and meaning of what data bits mean [2][3]. Also, new features
have been added [2]; there is now PCLKS 3 for example.

You can see few differences in following images. Same images were
attached in this mail:
[1] https://ibb.co/NmgbZmy - GAMACTRL_st7701.png
[2] https://ibb.co/G79y235 - PCLKS2.png

Thank you for your time,
Paulo

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