linux-kernel - Re: [PATCH V6 4/4] firmware: ti_sci: Introduce system suspend resume support

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Message-ID: <7ho7jgdsmq.fsf@baylibre.com>
Date:   Wed, 09 Aug 2023 10:37:17 -0700
From:   Kevin Hilman <khilman@...nel.org>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Dhruva Gole <d-gole@...com>, Andrew Davis <afd@...com>,
        Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Viresh Kumar <viresh.kumar@...aro.org>,
        Praneeth Bajjuri <praneeth@...com>,
        Dave Gerlach <d-gerlach@...com>,
        Vibhore Vardhan <vibhore@...com>, Georgi Vlaev <g-vlaev@...com>
Subject: Re: [PATCH V6 4/4] firmware: ti_sci: Introduce system suspend
 resume support

Tony Lindgren <tony@...mide.com> writes:

> * Kevin Hilman <khilman@...nel.org> [230809 00:20]:
>> To me, it sounds like you might want to use ->resume_early() or maybe
>> ->resume_noirq() in the pinctrl driver for this so that IO isolation can
>> be disabled sooner?
>
> For calls that need to happen just before the SoC is disabled or first
> thing on resume path, cpu_cluster_pm_enter() and cpu_cluster_pm_exit()
> notifiers work nice and allow distributing the code across the related
> SoC specific code and device drivers. See for example the usage in
> drivers/irqchip/irq-gic.c for CPU_CLUSTER_PM_ENTER.

Indeed, this is an option too, but for things that already have "full"
drivers (e.g. not an irqchip), they already have a full range of PM
callbacks, and adding another set of callbacks/notifiers for cpu_pm_* is
a bit clunky IMO.

That being said, for things like this IO isolation stuff that is
system-wide, and needs to happen very late in suspend (and/or very early
in suspend), cpu_pm_ is worth considering if the same cannot be done
with the normal PM callbacks.

Kevin