PM regression with commit 5de85b9d57ab PM runtime re-init in v4.5-rc1

[Tony Lindgren]

* Ulf Hansson <ulf.hansson at linaro.org> [160203 10:03]:
> 
> One more thing though. I just realized that you have yet another issue
> to consider going for the approach fixing *only* drivers.
> 
> Let me summarize it here:
> 
> If userspace has prevented runtime PM (pm_runtime_forbid()) when a
> driver becomes unbound, the driver will not be able to suspend the
> device by using any of the pm_runtime_suspend() APIs, as the usage
> count is isn't zero.
> 
> As pm_runtime_reinit() is invoked as part of the driver unbind
> sequence, the runtime PM status goes out of sync. A following driver
> rebind will then trigger the warning when the PM domain's
> ->runtime_resume() callback gets invoked. Again, forever preventing
> the device from being runtime suspended.

Hmm yeah that's a good point.

> How do you intend to solve this case?
> I guess there are two options, pick up the patch I posted for omap
> hwmod or make use of pm_runtime_force_suspend() in the driver.

My gut feeling right now is we should just have
BUS_NOTIFY_UNBIND_DRIVER shut down the device on the interconnect
automatically as it's unused after the driver has unloaded :)

Regards,

Tony