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

From: Kevin Hilman <khilman@kernel.org>
To: Tony Lindgren <tony@atomide.com>
Cc: Dhruva Gole <d-gole@ti.com>, Andrew Davis <afd@ti.com>,
	Nishanth Menon <nm@ti.com>, Tero Kristo <kristo@kernel.org>,
	Santosh Shilimkar <ssantosh@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Praneeth Bajjuri <praneeth@ti.com>,
	Dave Gerlach <d-gerlach@ti.com>, Vibhore Vardhan <vibhore@ti.com>,
	Georgi Vlaev <g-vlaev@ti.com>
Subject: Re: [PATCH V6 4/4] firmware: ti_sci: Introduce system suspend resume support
Date: Wed, 09 Aug 2023 10:37:17 -0700	[thread overview]
Message-ID: <7ho7jgdsmq.fsf@baylibre.com> (raw)
In-Reply-To: <20230809072330.GB11676@atomide.com>

Tony Lindgren <tony@atomide.com> writes:

> * Kevin Hilman <khilman@kernel.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