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

Alan Stern
2014-06-16T17:40:09Z

On Sat, 14 Jun 2014, Allen Yu wrote:

> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -608,7 +608,7 @@ static int rpm_resume(struct device *dev, int rpmflags)
> repeat:
> if (dev->power.runtime_error)
> retval = -EINVAL;
> - else if (dev->power.disable_depth == 1 && dev->power.is_suspended
> + else if (dev->power.disable_depth == 1 && !dev->power.is_suspended
> && dev->power.runtime_status == RPM_ACTIVE)
> retval = 1;

For reasons having nothing to do with Allen's suggested change, I
wonder if we shouldn't replace this line with something like:

- else if (dev->power.disable_depth == 1 && dev->power.is_suspended
+ else if (dev->power.disable > 0 && !dev->power.is_suspended
&& dev->power.runtime_status == RPM_ACTIVE)
retval = 1;

It seems that I've been bitten by this several times in the past.
When a device is disabled for runtime PM, and more or less permanently
stuck in the RPM_ACTIVE state, calls to pm_runtime_resume() or
pm_runtime_get_sync() shouldn't fail.

For example, suppose some devices of a certain type support runtime
power management but others don't. We naturally want to call
pm_runtime_disable() for the ones that don't. But we also want the
same driver to work for all the devices, which means that
pm_runtime_get_sync() should return success -- otherwise the driver
will think that something has gone wrong.

Rafael, what do you think?

Alan Stern