Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend

[Alan Stern]

On Sat, 26 Sep 2015, Rafael J. Wysocki wrote:

> > > So something like:
> > > 
> > > 	echo on >/sys/.../power/control  (in case the device was
> > > 			already in runtime suspend with wakeups enabled)
> > > 	echo off >/sys/.../power/wakeup
> > > 	echo auto >/sys/.../power/control

Cases where the driver wants to avoid runtime suspend (while the device
is active) because of bad wakeup support in the hardware can be handled
easily enough.  The runtime-idle or runtime-suspend callback routine
can check whether wakeup == off; if it isn't then the callback should
return -EBUSY.  Thus the driver can prevent runtime suspend without any
need to increment the usage counter.

> > That, or there may be an additional value, say "aggressive", to write to the
> > control file in which case it becomes just
> > 
> > echo aggressive >/sys/.../power/control
> 
> That said I suppose that the "off" value for the "wakeup" file might also be
> useful in some other cases, so it likely is a better approach.

We still need some sort of "inhibit" callback for cases where the
driver doesn't want to go into runtime suspend but does want to turn
off all I/O.  Should this callback be triggered when the user writes
"off" to power/wakeup, or when the user writes "inhibit" to
power/control, or should there be a separate sysfs attribute?

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/