Re: [PATCH 1/1] PM / Runtime: let rpm_resume fail if rpm disabled and device suspended.

Alan Stern
2014-06-20T14:48:13Z

On Fri, 20 Jun 2014, Rafael J. Wysocki wrote:

> > For a general device, the fact that dev->power.is_suspended is set
> > means the device _has_ been powered down. Even though the
> > runtime_status may not have changed, the PM core has to assume the
> > device is not available for use.
>
> This seems to go a bit too far. What power.is_suspended actually means is
> that __device_suspend() has run for the device successfully. What the
> implications of that are depends on the bus type (or subsystem in general)
> and device driver.
>
> > While your I2C devices may be useable even after the ->suspend callback
> > returns, for most devices this isn't true. So we shouldn't allow
> > rpm_resume() to return imediately when is_suspended is set.
>
> I can agree with that.

We really do need to decide more precisely how runtime PM and system PM
will interact. Should ->runtime_resume callbacks be allowed after
->suspend has returned?

Kevin has stated that some devices do need this ability. But most
don't. The PM core needs to handle these conflicting requirements
somehow.

Note: this is a separate issue from the meaning of disabled_depth > 0.

Alan Stern