Re: [PATCH v3 08/13] cpuidle: psci: Add a helper to attach a CPU to its PM domain

[Ulf Hansson <ulf.hansson@linaro.org>]

On Thu, 28 Nov 2019 at 15:15, Lorenzo Pieralisi
<lorenzo.pieralisi@arm.com> wrote:
>
> On Wed, Nov 27, 2019 at 11:29:09AM +0100, Ulf Hansson wrote:
>
> [...]
>
> > +struct device *psci_dt_attach_cpu(int cpu)
> > +{
> > +     struct device *dev;
> > +
> > +     /* Currently limit the hierarchical topology to be used in OSI mode. */
> > +     if (!psci_has_osi_support())
> > +             return NULL;
> > +
> > +     dev = dev_pm_domain_attach_by_name(get_cpu_device(cpu), "psci");
> > +     if (IS_ERR_OR_NULL(dev))
> > +             return dev;
> > +
> > +     pm_runtime_irq_safe(dev);
> > +     if (cpu_online(cpu))
>
> It is unclear to me how we handle (or rather we don't) CPU hotplug
> with this series - it does not look OK unless genpd code manages
> that automatically.

The series doesn't handle CPU hotplug at the moment, simply because I
am targeting to get the basic support, upstream first.

For a functionality point of view, this isn't a problem in my opinion.
Simply because the consequence is only that the idle states for the
"cluster" will not be reached if there is a CPU brought offline.

As we talked about at LPC and as also told Sudeep for the v2 series,
CPU hotplug is going to be implemented by using a CPU HP notifier.
That should be fine, right?

Kind regards
Uffe