linux-kernel - Re: [RFC PATCH 4/9] opp: core: Don't warn if required OPP device does not exist

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Date:   Tue, 12 Oct 2021 18:31:18 +0900
From:   "Hector Martin \"marcan\"" <marcan@...can.st>
To:     Viresh Kumar <viresh.kumar@...aro.org>
CC:     Sibi Sankar <sibis@...eaurora.org>,
        Saravana Kannan <saravanak@...gle.com>,
        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>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Viresh Kumar <vireshk@...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
Subject: Re: [RFC PATCH 4/9] opp: core: Don't warn if required OPP device does not exist



On 2021年10月12日 18:26:03 JST, Viresh Kumar <viresh.kumar@...aro.org> wrote:
>On 12-10-21, 14:57, Hector Martin wrote:
>> 
>> This is arguably not entirely representative of how the hardware works,
>> since technically the cluster switching couldn't care less what the memory
>> controller is doing; it's a soft dependency, states that should be switched
>> together but are not interdependent (in fact, the clock code does this
>> unconditionally after the CPU p-state change, regardless of whether we're
>> shifting up or down; this is, FWIW, the same order macOS uses, and it
>> clearly doesn't matter which way you do it).
>
>Yeah, I understand what you are doing. But the current patch is
>incorrect in the sense that it can cause a bug on other platforms. To
>make this work, you should rather set this genpd as parent of CPU
>devices (which are doing anyway since you are updating them with CPU's
>DVFS). With that the clk driver won't be required to do the magic
>behind the scene.
>

That doesn't work, though, because the CPUs aren't normal devices with runtime-pm. That was the first thing I tried :).

If you think this *should* be made to work instead then I can try that.


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