Re: calling runtime PM from system PM methods

On Sun, 19 Jun 2011, Rafael J. Wysocki wrote:

On Saturday, June 18, 2011, Rafael J. Wysocki wrote:

quoted

On Saturday, June 18, 2011, Alan Stern wrote:

quoted

On Sat, 18 Jun 2011, Rafael J. Wysocki wrote:

...

quoted

Well, assuming that https://patchwork.kernel.org/patch/893722/ is applied,
which is going to be, I think we can put

+       pm_runtime_get_noresume(dev);
+       pm_runtime_enable(dev);

in device_resume() after the dev->power.is_suspended check and
pm_runtime_put_noidle() under the End label.  That cause them to
be called under the device lock, but that shouldn't be a big deal.

Accordingly, we can call pm_runtime_disable(dev) in __device_suspend(),
right next to the setting of power.is_suspended.

This is implemented by the patch below.

Well, it hangs suspend on my Toshiba test box, I'm not sure why exactly.

This happens even if the pm_runtime_disable() is replaced with a version
that only increments the disable depth, so it looks like something down
the road relies on disable_depth being zero.  Which is worrisome.

This is a sign that the PM subsystem is getting a little too 
complicated.  :-(

Trying to figure out what the problem is I noticed that, for example,
the generic PM operations use pm_runtime_suspended() to decide whether or
not to execute system suspend callbacks, so the patch below would break it.

Also, after commit e8665002477f0278f84f898145b1f141ba26ee26 the
pm_runtime_suspended() check in __pm_generic_call() doesn't really make
sense.

In light of the recent changes, we should revisit the decisions behind 
the generic PM operations.

Alan Stern