On 3 February 2016 at 19:28, Tony Lindgren [off-list ref] wrote:

* Ulf Hansson [off-list ref] [160203 10:03]:

quoted

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.

quoted

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 :)

BUS_NOTIFY_UNBIND_DRIVER is sent prior the ->remove() callbacks is
invoked from driver core.
So if the driver requires to do a pm_runtime_get_sync() during
->remove() callback, this won't work.

BUS_NOTIFY_UNBOUND_DRIVER may work though.

Kind regards
Uffe