linux-kernel - Re: [PATCH 1/9] dt-bindings: display: Add yamls for JH7110 display subsystem

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Message-ID: <ifgjvonhkzcwrklzch5efguor2x6az4m737dwte4uyow7ar5dr@z4glaxse6dou>
Date:   Wed, 7 Jun 2023 08:41:04 +0200
From:   Maxime Ripard <mripard@...nel.org>
To:     Conor Dooley <conor@...nel.org>
Cc:     Heiko Stübner <heiko@...ech.de>,
        Keith Zhao <keith.zhao@...rfivetech.com>,
        Shengyu Qu <wiagn233@...look.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        christian.koenig@....com, Bjorn Andersson <andersson@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>, Jagan Teki <jagan@...eble.ai>,
        Chris Morgan <macromorgan@...mail.com>,
        Jack Zhu <jack.zhu@...rfivetech.com>,
        Shengyang Chen <shengyang.chen@...rfivetech.com>,
        Changhuang Liang <changhuang.liang@...rfivetech.com>
Subject: Re: [PATCH 1/9] dt-bindings: display: Add yamls for JH7110 display
 subsystem

On Tue, Jun 06, 2023 at 11:37:53PM +0100, Conor Dooley wrote:
> On Wed, Jun 07, 2023 at 12:22:33AM +0200, Heiko Stübner wrote:
> > Am Dienstag, 6. Juni 2023, 20:41:17 CEST schrieb Shengyu Qu:
> > > > On Fri, Jun 02, 2023 at 03:40:35PM +0800, Keith Zhao wrote:
> > > >> Add bindings for JH7110 display subsystem which
> > > >> has a display controller verisilicon dc8200
> > > >> and an HDMI interface.
> 
> > > >> +description:
> > > >> +  The StarFive SoC uses the HDMI signal transmiter based on innosilicon IP
> > > > Is innosilicon the same thing as verisilicon? Also
> > > > s/transmiter/transmitter/, both here and in the title.
> > > 
> > > I think that is not the same, I remember Rockchip has used a HDMI 
> > > transmitter from
> > > 
> > > Innosilicon, and there is a existing driver for that in mainline.
> > 
> > Yep, I think Innosilicon is the company you turn to when you want to save
> > a bit of money ;-) . In the bigger SoCs Rockchip most of the time uses
> > Designware hdmi blocks and looking at the history only the rk3036 ever
> > used an Innosilicon block.
> > 
> > Looking at the history, 2016 really was a long time ago :-D.
> > 
> > > So Keith, if that's true, I think it is better to seperate the HDMI 
> > > stuff and reuse existing driver.
> > 
> > I'm not so sure about that - at least from a cursory glance :-) .
> > 
> > The registers do look slightly different and I don't know how much
> > the IP changed between the rk3036-version and the jh7110 version.
> > 
> > At the very least, I know my rk3036 board isn't booting right now, so
> > I can't really provide help for generalizing the rockchip-driver.
> > 
> > At the very least both the binding and driver could drop the "starfive-hdmi"
> > and actually use the Innosilicon in the naming somewhere, so that it's
> > clear for future developers :-)
> 
> Seeing "based on" always makes me a little bit nervous to be honest when
> it comes to using a compatible from the IP. Is it the IP? What version
> is it? etc. Perhaps "starfive,jh7110-hdmi" & falling back to some sort
> of "innosilicon,hdmi" would be more future/IP-silliness proof.
> Driver can always be generic & bind against "innosilicon,hdmi" until
> that becomes impossible.

Given that Neil was saying that there's at least two
generations/revisions/models of an HDMI controller from Innosilicon, I'm
not sure that compatible is enough to reach that goal anyway.

Maxime

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