linux-kernel - Re: [PATCH] PM: s2idle: Introduce syscore callbacks in s2idle flow

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Message-ID: <CAJZ5v0hOGEUamXw124q4CnL67o97qRHy9Vv9_F2AQqefDdu3vQ@mail.gmail.com>
Date:   Tue, 1 Sep 2020 13:57:33 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Claude Yen <claude.yen@...iatek.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC..." 
        <linux-mediatek@...ts.infradead.org>,
        wsd_upstream <wsd_upstream@...iatek.com>
Subject: Re: [PATCH] PM: s2idle: Introduce syscore callbacks in s2idle flow

On Tue, Sep 1, 2020 at 9:05 AM Claude Yen <claude.yen@...iatek.com> wrote:
>
> This series based on 5.9-rc1
> This patch makes s2idle call existing syscore callbacks. Currently,
> when s2idle is selected as system suspend method, callbacks hooked
> by register_syscore_ops() will not be triggered. This may induce
> unexpected results.

They are not executed by design.

> For example, sched_clock_suspend() was added to s2idle flow in
> commit 3f2552f7e9c5 ("timers/sched_clock: Prevent generic sched_clock
> wrap caused by tick_freeze()") to fix clock wrap problem. However,
> sched_clock_suspend() is originally registered in syscore callback.

I'm not sure why this matters here.

> With this patch, if another syscore callback is needed in s2idle,
> additional migration effort could be saved.

s2idle cannot execute syscore callbacks, because it doesn' take
non-boot CPUs offline and it won't do that.

Thanks!