linux-kernel - Re: [PATCH v2 2/2] dt-bindings: regulator: Add bindings for Unisoc's SC2730 regulator

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Date:   Mon, 26 Sep 2022 07:59:08 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Chunyan Zhang <zhang.lyra@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        Baolin Wang <baolin.wang7@...il.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Chunyan Zhang <chunyan.zhang@...soc.com>,
        LKML <linux-kernel@...r.kernel.org>, Lee Jones <lee@...nel.org>
Subject: Re: [PATCH v2 2/2] dt-bindings: regulator: Add bindings for Unisoc's
 SC2730 regulator

On Thu, 22 Sep 2022, Mark Brown wrote:

> On Thu, Sep 22, 2022 at 11:19:08AM +0100, Lee Jones wrote:
> > On Thu, 22 Sep 2022, Chunyan Zhang wrote:
> 
> > > I understand your point. But like I described previously [1], if we
> > > still use the current solution (i.e. use devm_of_platform_populate()
> > > to register MFD subdevices), a compatible string is required. I'm open
> > > to switching to other solutions, do you have some suggestions?
> > 
> > Many IPs encompassing multiple functions are described that way in
> > DT.  I don't have the details for *this* device to hand, so my
> > comments here aren't specific to this use-case, but describing each
> > function individually does describe the H/W accurately, which is all
> > DT calls for.
> 
> If people want to describe the individual regulators that'd be
> less of an issue, it's mainly when you're nesting what's
> effectively another MFD within a parent MFD that it's just noise
> that's being added to the DT.

As I say, I haven't studied this use-case.

These comments were designed to be more generic.

What do you mean by nested MFDs?

> > Can you imagine describing an SoC, which can be considered as a huge
> > MFD, with only a single node?
> 
> Honestly we should be arranging things so they're more like that,
> at least using overlays for the internals of the SoC so you don't
> have to rebuild the whole DT for updates to the SoC internals.

Right, there would be one device root node.  However each function;
clock providers, regulator controllers, PWMs, GPIOs, networking
(various), reset, watchdog, etc would have their own nodes.  Rather
than attempting to describe everything in the parent's node.

-- 
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