Re: [BUG] Device unbound in a resumed state

From: Alan Stern
Date: Fri Mar 11 2016 - 13:46:29 EST

On Fri, 11 Mar 2016, Krzysztof Kozlowski wrote:

> Hi,
> Could be related (the same?) with [0].
> I have a driver (hwrng/exynos-rng) which in probe does:
> pm_runtime_set_autosuspend_delay(&pdev->dev, EXYNOS_AUTOSUSPEND_DELAY);
> pm_runtime_use_autosuspend(&pdev->dev);
> pm_runtime_enable(&pdev->dev);
> and in remove:
> pm_runtime_disable(&pdev->dev)

But not pm_runtime_dont_use_autosuspend()?

Why disable runtime PM if you want the runtime-PM methods to put the
device into a low-power state?

> Just before unbinding in __device_release_driver() the device is resumed
> but unfortunately not suspended later. I mean the
> __device_release_driver()->pm_runtime_put_sync() does not trigger
> runtime suspend.

Because autosuspend is still in use at this point.

> This leads to leaving the device in active state (e.g. clocks enabled).
> It does not happen after removal of autosuspend. Also runtime suspend
> happens after very fast unbind-bind.

Overall it sounds like the system is behaving the way it is supposed

But maybe we should make pm_runtime_use_autosuspend() call
pm_runtime_mark_last_busy(), to avoid the unbind - bind - immediate
autosuspend behavior.

Alan Stern