Re: [PATCH v2 1/3] phy: core: Move runtime PM reference counting to the parent device

From: Rafael J. Wysocki
Date: Wed Dec 20 2017 - 20:39:25 EST

On Wed, Dec 20, 2017 at 3:09 PM, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> The runtime PM deployment in the phy core is deployed using the phy core
> device, which is created by the phy core and assigned as a child device of
> the phy provider device.
> The behaviour around the runtime PM deployment cause some issues during
> system suspend, in cases when the phy provider device is put into a low
> power state via a call to the pm_runtime_force_suspend() helper, as is the
> case for a Renesas SoC, which has its phy provider device attached to the
> generic PM domain.
> In more detail, the problem in this case is that pm_runtime_force_suspend()
> expects the child device of the provider device, which is the phy core
> device, to be runtime suspended, else a WARN splat will be printed
> (correctly) when runtime PM gets re-enabled at system resume.

So we are now trying to work around issues with
pm_runtime_force_suspend(). Lovely. :-/

> In the current scenario, even if a call to phy_power_off() triggers it to
> invoke pm_runtime_put() during system suspend, the phy core device doesn't
> get runtime suspended, because this is prevented in the system suspend
> phases by the PM core.
> To solve this problem, let's move the runtime PM deployment from the phy
> core device to the phy provider device, as this provides the similar
> behaviour. Changing this makes it redundant to enable runtime PM for the
> phy core device, so let's avoid doing that.

I'm not really convinced that this approach is the best one to be honest.

I'll have a deeper look at this in the next few days, stay tuned.