linux-kernel - Re: [RFC PATCH 3/9] dt-bindings: clock: Add apple,cluster-clk binding

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Date:   Tue, 12 Oct 2021 22:48:09 +0900
From:   Hector Martin <marcan@...can.st>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Hector Martin <marcan@...can.st>,
        linux-arm-kernel@...ts.infradead.org,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Sven Peter <sven@...npeter.dev>, Marc Zyngier <maz@...nel.org>,
        Mark Kettenis <mark.kettenis@...all.nl>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, Nishanth Menon <nm@...com>,
        Catalin Marinas <catalin.marinas@....com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Subject: Re: [RFC PATCH 3/9] dt-bindings: clock: Add apple,cluster-clk binding

On 12/10/2021 18.57, Viresh Kumar wrote:
> I didn't realize earlier that we have moved out of lists :)

Whoops, sorry, I was on mobile and must've hit the wrong reply button! 
My apologies.

> On 12-10-21, 18:54, Hector Martin "marcan" wrote:
>> Typically cpufreq-dt is used with clock drivers that directly take
>> the clock frequency and do whatever voodoo is necessary to set it
>> for the CPU. But here, the hardware just wants to know the index,
>> and does everything itself. So we need to encode that somewhere, to
>> avoid hardcoding it in the clock driver.
>>
>> In general, based on how these SoCs are designed, we're trying to
>> avoid having tables of volatile information in the drivers, and
>> instead keep everything in the DT. This means we have a good chance
>> that these drivers will continue to work with future SoC
>> generations, since Apple doesn't change register definitions
>> randomly most of the time.
> 
> Yeah I get that and it is actually better this way. I just wanted to
> point out that we didn't think of it this way earlier :)

Yeah, makes sense. Seems to work fine :)


-- 
Hector Martin (marcan@...can.st)
Public Key: https://mrcn.st/pub