Re: [linux-pm] subtle pm_runtime_put_sync race and sdio functions

[Johannes Berg <johannes@sipsolutions.net>]

On Sat, 2010-12-18 at 18:00 +0200, Ohad Ben-Cohen wrote:

> > That's where the problem is.  If there's a difference, from the driver's
> > point of view, between suspend and some other operation, there should be a
> > way to tell the driver what case it actually is dealing with.
> 
> Yes, the problem will be solved if the driver would bypass the runtime
> PM framework on system suspend. mac80211 obviously has this
> information, and technically it's very easy to let the driver know
> about it.
> 
> But the difference between suspend and normal operation is really
> artificial: in both cases mac80211 just asks the driver to power its
> device down, and the end result is exactly the same (a GPIO line of
> the device is de-asserted in our case). The difference between these
> two scenarios
> exist only because runtime PM is effectively disabled during system
> suspend, and therefore the driver has to look for an alternative way
> to power down the device.

Sounds to me like the difference isn't really in the driver, but the
core PM subsystem. Why does it care when powering off a device whether
it's during suspend, or during runtime?

johannes