linux-kernel - Re: [patch update] Re: [linux-pm] Run-time PM idea (was: Re: [RFC][PATCH 0/2] PM: Rearrange core suspend code)

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Message-Id: <200906111108.40785.oliver@neukum.org>
Date:	Thu, 11 Jun 2009 11:08:40 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Magnus Damm <magnus.damm@...il.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-pm@...ts.linux-foundation.org,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch update] Re: [linux-pm] Run-time PM idea (was: Re: [RFC][PATCH 0/2] PM: Rearrange core suspend code)

Am Donnerstag, 11. Juni 2009 07:18:46 schrieb Magnus Damm:
> 3) When all devices in the power domain are suspended the bus code can
> turn off the power. The reason why I'd like to only autosuspend when

So you are saying that you have power dependencies independent
of the device tree?

> all devices are idle is simply that we don't get any power savings
> from the per device autosuspend() callbacks, only from turning off
> power to the entire per-domain. So bindly autosuspending and
> autoresuming devices is just pure overhead unless we know we can do it
> for all devices in the domain.

Why can't you do this within the framework? You simply suspend when
all a domain's devices have been autosuspended.
I suppose we could have a helper.

int pm_autosuspend_in_domain(struct device *dev)
{
	int err;

	mutex_lock(dev->power_domain);
	if (! --dev->power_domain.active_devices)
		err = dev->power_domain->power_down(dev->power_domain);
	else
		err = 0;
	mutex_unlock(dev->power_domain);

	return err;
}

	Regards
		Oliver

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