linux-kernel - RE: [PATCH 1/1] driver core: disable device's runtime pm during shutdown

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Message-ID: <35AB98346D25394A9354ED89C4D7658722905B@039-SN1MPN1-002.039d.mgd.msft.net>
Date:	Mon, 5 Dec 2011 08:32:27 +0000
From:	Chen Peter-B29397 <B29397@...escale.com>
To:	NeilBrown <neilb@...e.de>
CC:	Ming Lei <tom.leiming@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Greg KH <greg@...ah.com>,
	"gregkh@...e.de" <gregkh@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"stern@...land.harvard.edu" <stern@...land.harvard.edu>,
	"hzpeterchen@...il.com" <hzpeterchen@...il.com>,
	Igor Grinberg <grinberg@...pulab.co.il>
Subject: RE: [PATCH 1/1] driver core: disable device's runtime pm during
 shutdown

 
> > > stays
> > > > > asleep, omap_i2c_xfer cannot wake it, the transfer doesn't happen
> and
> > > the
> > > > > system doesn't get powered off.
> > > > >
> > > > > So here is a device that should *not* have pm disabled at
> shutdown.
> > > > >
> > > > > So I feel this fix is a little too heavy-handed.
> > > >
> > > > Maybe the device's runtime PM should not be disabled if
> > > > there is no ->shutdown defined in its driver, how about the blew?
> > >
> > > Thanks, but that won't actually help.
> > >
> > > dev->bus->shutdown is i2c_device_shutdown so there is a shutdown
> method.
> > > However i2c_device_shutdown just finds the driver can calls
> > > driver->shutdown(), and that is the 'shutdown' that is NULL.
> > >
> > Then, i2c should be registered before than twl4030 as a platform device,
> since
> > twl4030 is an i2c device. Just let i2c shut down later than twl4030's.
> 
> It almost certainly is, but that is totally irrelevant.
> 
> The problem has nothing to do with ordering and nothing much to do with
> ->shutdown() being called.
> 
> The problem is simply that pm_runtime_disable() is being called on all
> devices, and that stops devices that are asleep from waking up.
> 
Please correct me if I am wrong
1. This change only affects when the user issues "reboot" or "shutdown"
2. The pm_runtime_disable(dev) is only be called before this "dev" is
coming to shutdown
3. If i2c bus/driver->shutdown is not called, its runtime pm is still enabled.
4. You may issue i2c xfer after i2c bus/driver->shutdown is called.  

> I think the intention of putting that call in was to stop devices that
> are
> awake from going to sleep, and maybe that is justified.  But stopping
> devices
> that are asleep from waking up isn't.
> 
> NeilBrown
> 
> 
> >
> > > Thanks,
> > > NeilBrown
> > >
> > >
> > >


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