linux-kernel - Re: [PATCH v6 00/25] PM / Domains: Support hierarchical CPU arrangement (PSCI/ARM)

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Message-ID: <20180314171914.tdwtppsvjsgxiqlv@lakrids.cambridge.arm.com>
Date:   Wed, 14 Mar 2018 17:19:15 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        linux-pm@...r.kernel.org, Kevin Hilman <khilman@...nel.org>,
        Lina Iyer <ilina@...eaurora.org>,
        Lina Iyer <lina.iyer@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Juri Lelli <juri.lelli@....com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 00/25] PM / Domains: Support hierarchical CPU
 arrangement (PSCI/ARM)

Hi Ulf,

On Wed, Mar 14, 2018 at 05:58:10PM +0100, Ulf Hansson wrote:
> For ARM, the PSCI firmware interface may be managing the power to the CPUs.
> Depending on the SoC, CPUs may also be arranged in hierarchical manner, which
> could add another level of complexity from a CPU idle management point of view.
> 
> PSCI v1.0+ adds support for the so called OS initiated CPU suspend mode, which
> enables a more fine grained method, allowing Linux to get more control, in
> regards to being energy efficient. This is typically useful for these kind of
> complex battery driven platforms.

> The series is based on v4.16-rc5, but applies also as of today to Rafael's
> linux-pm.git next branch. The code has been tested on a QCOM 410c dragonboard
> and I except that test coverage should be increased by some more boards
> shortly (for ARM64 with PSCI OSI support - only a few DT changes are needed).

Do we have any numbers to show how this affects energy efficiency?

Are there any other platforms with OSI support?

Thanks,
Mark.