linux-kernel - Re: platform/i2c busses: pm runtime and system sleep

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Message-ID: <20101217142402.GA19391@rakim.wolfsonmicro.main>
Date:	Fri, 17 Dec 2010 14:24:03 +0000
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Rabin Vincent <rabin@....in>, stern@...land.harvard.edu,
	linux-pm@...ts.linux-foundation.org, linux-i2c@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: platform/i2c busses: pm runtime and system sleep

On Fri, Dec 17, 2010 at 02:49:25PM +0100, Rafael J. Wysocki wrote:
> On Friday, December 17, 2010, Mark Brown wrote:

> > By, for example, providing default implementations which the buses can
> > use if they choose to.

> OK, so we have generic_subsys_pm_ops.  Do we need anything beyond that?

Hrm.  Possibly just some fiddling with those or alternative versions.
For example, looking at the I2C bus suspend it's this:

static int i2c_device_pm_suspend(struct device *dev)
{
	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

	if (pm) {
		if (pm_runtime_suspended(dev))
			return 0;
		else
			return pm->suspend ? pm->suspend(dev) : 0;
	}

	return i2c_legacy_suspend(dev, PMSG_SUSPEND);
}

Ideally the if (pm) block could just be factored out into the pm core as
there's nothing I2C-specific about that at all.  Possibly even the whole
logic surrounding fall back to legacy, though that smells a bit.  The
generic suspend operation doesn't fit here:

int pm_generic_suspend(struct device *dev)
{
	return __pm_generic_call(dev, PM_EVENT_SUSPEND);
}
EXPORT_SYMBOL_GPL(pm_generic_suspend);
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