Subject: Re: [PATCH 15/18] drivers: firmware: psci: Support CPU hotplug for the hierarchical model

From: Sudeep Holla <[email-masked]>
Date: Fri, 7 Jun 2019 16:31:14 +0100

On Mon, May 13, 2019 at 09:22:57PM +0200, Ulf Hansson wrote:
> When the hierarchical CPU topology is used and when a CPU has been put
> offline (hotplug), that same CPU prevents its PM domain and thus also
> potential master PM domains, from being powered off. This is because genpd
> observes the CPU's attached device as being active from a runtime PM point
> of view.
> 
> To deal with this, let's decrease the runtime PM usage count by calling
> pm_runtime_put_sync_suspend() of the attached struct device when putting
> the CPU offline. Consequentially, we must then increase the runtime PM
> usage count, while putting the CPU online again.
> 

Why is this firmware/driver specific ? Why can't this be dealt in core
pm-domain ? I am concerned that if any other architectures or firmware
method decides to use this feature, this need to be duplicated there.

The way I see this is pure reference counting and is hardware/firmware/
driver agnostic and can be made generic.

--
Regards,
Sudeep

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