linux-kernel - Re: [PATCH 0/3] Apple M1 clock gate driver

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Message-Id: <9ff6ec26-4b78-4684-9c23-16d5cbfef857@www.fastmail.com>
Date:   Sun, 30 May 2021 13:08:40 +0200
From:   "Sven Peter" <sven@...npeter.dev>
To:     "Tony Lindgren" <tony@...mide.com>,
        "Rob Herring" <robh+dt@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-clk <linux-clk@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Hector Martin" <marcan@...can.st>,
        "Michael Turquette" <mturquette@...libre.com>,
        "Stephen Boyd" <sboyd@...nel.org>,
        "Mark Kettenis" <mark.kettenis@...all.nl>,
        "Arnd Bergmann" <arnd@...nel.org>
Subject: Re: [PATCH 0/3] Apple M1 clock gate driver

Hi,

On Wed, May 26, 2021, at 09:18, Tony Lindgren wrote:
> Hi,
> 
> * Rob Herring <robh+dt@...nel.org> [210525 18:09]:
> > I would do a single node per mmio region with the register offset (or
> > offset / 4) being the clock id. This can still support new SoCs easily
> > if you have a fallback compatible. If you want/need to get all the
> > clocks, just walk the DT 'clocks' properties and extract all the IDs.
> 
> I mostly agree.. Except I'd also leave out the artificial clock ID and
> just use real register offsets from the clock controller base instead.

Sure, I'll do that.

> 
> So a single clock controller node for each MMIO range, then set
> #clock=cells = <1>. Then the binding follows what we have for the
> interrupts-extended binding for example.
> 
> If the clock controller optionally needs some data in the dts,
> that can be added to the clock controller node. Or it can be driver
> internal built-in data. If the data for dts can be described in a
> generic way, even better :)

Now the big question is *how* to describe this additional data in the
dts. Essentially I need to specify that e.g. to enable clock 0x270
I first need to enable the (internal) clocks 0x1c0 and then 0x220.
Are you aware of any generic way to describe this? I'm not even sure
how a sane non-generic way would look like when I just have a single
clock controller node.



Best,

Sven