linux-kernel - Re: [PATCH v2 0/4] Apple SoC cpufreq driver

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Date:   Wed, 4 May 2022 21:30:19 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Hector Martin <marcan@...can.st>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Marc Zyngier <maz@...nel.org>,
        Mark Kettenis <mark.kettenis@...all.nl>,
        linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/4] Apple SoC cpufreq driver

Hi Viresh,

On Wed, May 04, 2022 at 03:57:45PM +0530, Viresh Kumar wrote:
> On 04-05-22, 16:51, Hector Martin wrote:
> > Hi folks,
> > 
> > Here's a second take on the cpufreq driver for Apple SoCs. This is a
> > complete rewrite using a stand-alone cpufreq driver instead of using the
> > cpufreq-dt infrastructure.
> > 
> > Since v1 we ran some experiments on the memory controller performance
> > switching and it turns out it doesn't make a huge difference, so it
> > makes sense to punt that feature to the future (perhaps once a proper
> > memory controller driver exists for other reasons, e.g. for error
> > handling).
> > 
> > One advantage of having a standalone cpufreq driver is that we can
> > support fast switching. This also means any future interaction with
> > the memory controller will probably use some bespoke mechanism instead
> > of the genpd infrastructure, so we can keep the fast path without
> > allowing sleeps/etc.
> > 
> > The driver is based on scpi-cpufreq.c, with some bits (e.g. the
> > apple,freq-domain stuff) inspired by how cpufreq-qcom-hw does it.
> > I'm not sure if that particular property should be described
> > in a binding, since it goes in the cpu nodes (qcom doesn't have it
> > anywhere...).
> 
> Hi Mani,
> 
> I can see that Rob asked you to add this somewhere, maybe in arm/cpu
> stuff, but I don't think you ever sent a patch with that. What
> happened ?
> 
> https://lore.kernel.org/lkml/20201013171800.GA3716411@bogus/
> 

Oops. Looks like that one slipped through the cracks. I did add it to my todo
list for qcom-cpufreq but missed it completely.

I will look into it.

Thanks,
Mani

> -- 
> viresh