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Date:   Fri, 7 Jun 2019 16:31:14 +0100
From:   Sudeep Holla <sudeep.holla@arm.com>
To:     Ulf Hansson <ulf.hansson@linaro.org>
Cc:     Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        linux-arm-kernel@lists.infradead.org,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        "Raju P . L . S . S . S . N" <rplsssn@codeaurora.org>,
        Amit Kucheria <amit.kucheria@linaro.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Stephen Boyd <sboyd@kernel.org>,
        Niklas Cassel <niklas.cassel@linaro.org>,
        Tony Lindgren <tony@atomide.com>,
        Kevin Hilman <khilman@kernel.org>,
        Lina Iyer <ilina@codeaurora.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Souvik Chakravarty <souvik.chakravarty@arm.com>,
        Sudeep Holla <sudeep.holla@arm.com>, linux-pm@vger.kernel.org,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 15/18] drivers: firmware: psci: Support CPU hotplug for
 the hierarchical model
Message-ID: <20190607153114.GI15577@e107155-lin>
References: <20190513192300.653-1-ulf.hansson@linaro.org>
 <20190513192300.653-16-ulf.hansson@linaro.org>
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On Mon, May 13, 2019 at 09:22:57PM +0200, Ulf Hansson wrote:
> When the hierarchical CPU topology is used and when a CPU has been put
> offline (hotplug), that same CPU prevents its PM domain and thus also
> potential master PM domains, from being powered off. This is because genpd
> observes the CPU's attached device as being active from a runtime PM point
> of view.
> 
> To deal with this, let's decrease the runtime PM usage count by calling
> pm_runtime_put_sync_suspend() of the attached struct device when putting
> the CPU offline. Consequentially, we must then increase the runtime PM
> usage count, while putting the CPU online again.
> 

Why is this firmware/driver specific ? Why can't this be dealt in core
pm-domain ? I am concerned that if any other architectures or firmware
method decides to use this feature, this need to be duplicated there.

The way I see this is pure reference counting and is hardware/firmware/
driver agnostic and can be made generic.

--
Regards,
Sudeep