linux-kernel - Re: [PATCH v2 7/7] arm64: dts: allwinner: a64: enable ANX6345 bridge on Teres-I

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Message-ID: <20190709142155.2blclgbqapjeifv3@flea>
Date:   Tue, 9 Jul 2019 16:21:55 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Icenowy Zheng <icenowy@...c.io>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Vasily Khoruzhick <anarsoul@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        devicetree <devicetree@...r.kernel.org>,
        Sean Paul <seanpaul@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Torsten Duwe <duwe@....de>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Harald Geyer <harald@...ib.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 7/7] arm64: dts: allwinner: a64: enable ANX6345 bridge
 on Teres-I

On Tue, Jul 09, 2019 at 04:58:35PM +0800, Icenowy Zheng wrote:
>
>
> 于 2019年7月9日 GMT+08:00 下午4:55:32, Maxime Ripard <maxime.ripard@...tlin.com> 写到:
> >On Mon, Jul 08, 2019 at 05:49:21PM -0700, Vasily Khoruzhick wrote:
> >> > > Maybe instead of edp-connector one would introduce integrator's
> >specific
> >> > > connector, for example with compatible
> >"olimex,teres-edp-connector"
> >> > > which should follow edp abstract connector rules? This will be at
> >least
> >> > > consistent with below presentation[1] - eDP requirements depends
> >on
> >> > > integrator. Then if olimex has standard way of dealing with
> >panels
> >> > > present in olimex/teres platforms the driver would then create
> >> > > drm_panel/drm_connector/drm_bridge(?) according to these rules, I
> >guess.
> >> > > Anyway it still looks fishy for me :), maybe because I am not
> >> > > familiarized with details of these platforms.
> >> >
> >> > That makes sense yes
> >>
> >> Actually, it makes no sense at all. Current implementation for
> >anx6345
> >> driver works fine as is with any panel specified assuming panel
> >delays
> >> are long enough for connected panel. It just doesn't use panel
> >timings
> >> from the driver. Creating a platform driver for connector itself
> >looks
> >> redundant since it can't be reused, it doesn't describe actual
> >> hardware and it's just defeats purpose of DT by introducing
> >> board-specific code.
> >
> >I'm not sure where you got the idea that the purpose of DT is to not
> >have any board-specific code.
> >
> >It's perfectly fine to have some, that's even why there's a compatible
> >assigned to each and every board.
> >
> >What the DT is about is allowing us to have a generic behaviour that
> >we can detect: we can have a given behaviour for a given board, and a
> >separate one for another one, and this will be evaluated at runtime.
> >
> >This is *exactly* what this is about: we can have a compatible that
> >sets a given, more specific, behaviour (olimex,teres-edp-connector)
> >while saying that this is compatible with the generic behaviour
> >(edp-connector). That way, any OS will know what quirk to apply if
> >needed, and if not that it can use the generic behaviour.
> >
> >And we could create a generic driver, for the generic behaviour if
> >needed.
> >
> >> There's another issue: if we introduce edp-connector we'll have to
> >> specify power up delays somewhere (in dts? or in platform driver?),
> >so
> >> edp-connector doesn't really solve the issue of multiple panels with
> >> same motherboard.
> >
> >And that's what that compatible is about :)
>
> Maybe we can introduce a connector w/o any driver just like hdmi-connector?

Ironically, a driver for it has been sent yesterday :)

But yeah, we can definitely do that too.

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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