linux-kernel - Re: [PATCH/RFC 4/5] ARM: shmobile: R-Mobile: Add DT support for PM domains

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Date:	Tue, 09 Sep 2014 09:11:18 -0700
From:	Kevin Hilman <khilman@...nel.org>
To:	Geert Uytterhoeven <geert+renesas@...der.be>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Simon Horman <horms@...ge.net.au>,
	Magnus Damm <magnus.damm@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Philipp Zabel <philipp.zabel@...il.com>,
	linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
	linux-sh@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH/RFC 4/5] ARM: shmobile: R-Mobile: Add DT support for PM domains

Geert Uytterhoeven <geert+renesas@...der.be> writes:

> Populate the PM domains from DT, and provide support to hook up devices
> to their respective PM domain.
>
> The always-on power area (e.g. C5 on r8a7740) is created as a PM domain
> without software control, to allow Run-Time management of module clocks
> for hardware blocks inside this area in the future.
> Power-on/off latencies are supported.
>
> Limitations and special cases in the non-DT case are handled through
> rmobile_pm_quirks(). Checks for hardcoded PM domain indices should be
> replaced by the analysis of relations between devices and PM domains in
> DT.
>
> Initialization is done from core_initcall(), as the
> "renesas,intc-irqpin" driver uses postcore_initcall().
>
> This is functionally almost equivalent to the non-DT case. Missing are
> Run-Time management of the module clocks (pm_clk_*()), and device
> latencies.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>

[...]

This series looks really good to me.  Just a minor question about a
possible next step...

> +static int r8a7740_pd_a4s_suspend(void)
> +{
> +	/*
> +	 * The A4S domain contains the CPU core and therefore it should
> +	 * only be turned off if the CPU is in use.
> +	 */
> +	return -EBUSY;
> +}


Do you have plans to use pm_genpd_attach_cpuidle() for this eventually,
maybe by checking if the enclosing node is a CPU?  If not, are there
other plans to handle idle for the power domains that contain CPUs?

Kevin
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