Re: [PATCH v6 04/10] PM / EM: add support for other devices than CPUs in Energy Model

[Lukasz Luba]

On 4/23/20 4:12 PM, Daniel Lezcano wrote:
> On Fri, Apr 10, 2020 at 09:42:04AM +0100, Lukasz Luba wrote:
> > Add support for other devices that CPUs. The registration function
> > does not require a valid cpumask pointer and is ready to handle new
> > devices. Some of the internal structures has been reorganized in order to
> > keep consistent view (like removing per_cpu pd pointers). To track usage
> > of the Energy Model structures, they are protected with kref.
>
> Why not add the energy model structure in the struct device directly?

Do you mean this structure?
https://elixir.bootlin.com/linux/latest/source/include/linux/device.h#L537

and to put something like:
struct device {
...
	struct dev_pm_domain	*pm_domain;
#ifdef CONFIG_ENERGY_MODEL
	struct em_perf_domain	*em_pd;
#endif
...
};

> For instance for the em_cpu_get() function, the cpu id allows to retrieve the
> cpu device and then from there, the energy model instead of browsing another
> list. The em_device life cycle will be tied to the struct device.

That would be perfect.

> Then when the struct device and the em_device are connected, add the debugfs
> with a struct device list for those which are energy aware, so you end up with
> a structure:
>
> struct em_device {
> 	struct device *dev;
> 	struct list_head em_dev_list;
> };
>
> (a global single dentry for debugfs to do a recursive delete is enough).
>
> Locks when inspecting and add/removal called from the struct device release
> function. So no need of an extra refcounting.
>
> Does it make sense?

Indeed it looks much cleaner/simpler.

I will try to address this idea and get rid of refcounting.

This should be doable in this patch (4/10). In the v7 I will keep your
ACKs for other patches that you have already commented.

Thank you for your suggestions and review.

Regards,
Lukasz