Re: [RFC PATCH v6 6/9] thermal: cpu_cooling: implement the power cooling device API

Javi Merino
2014-12-09T10:32:55Z

Hi Viresh,

On Tue, Dec 09, 2014 at 01:59:39AM +0000, Viresh Kumar wrote:
> On 8 December 2014 at 19:52, Javi Merino <javi.merino@arm.com> wrote:
> > Ok, changed it into:
> >
> > cpu = cpumask_any(&cpufreq_device->allowed_cpus);
> > dev = get_cpu_device(cpu);
> > if (!dev) {
> > dev_warn(&cpufreq_device->cool_dev->device,
> > "No cpu device for cpu %d\n", cpu);
> > ret = -EINVAL;
> > goto unlock;
> > }
> >
> > num_opps = dev_pm_opp_get_opp_count(dev);
> > if (num_opps <= 0) {
> > ret = (num_opps < 0)? num_opps : -EINVAL;
> > goto unlock;
> > }
>
> And this might not work. This is what I said in the first reply.
>
> So, a bit lengthy reply now :)
>
> Every cpu has a device struct associated with it. When cpufreq
> core initializes drivers, they ask for mapping (initializing) the opps.
> At that point we pass policy->cpu to opp core. OPP core doesn't
> know which cores share clock line (I am trying to solve that [1]) and
> so it just initializes the OPPs for policy->cpu. Let us say it cpuX.
>
> Now there will be few more CPUs which are going to share clock
> line with it and hence will use the same OPPs. In thermal core,
> you got clip_cpus which is exactly the masks of all these CPUs
> sharing clock line.
>
> If the OPP layer is good enough, then above code can work. But
> because right now the OPPs are mapped to just cpuX, passing
> any other cpu from clip_cpus will fail as it doesn't have any associated
> OPPs.
>
> Now what I asked you is to use the CPU for which
> __cpufreq_cooling_register() is called. Normally we are calling
> __cpufreq_cooling_register() for the CPU for which OPPs are
> registered (but people might call it up for other CPUs as well)..

Sorry but I don't follow. __cpufreq_cooling_register() is passed a
clip_cpus mask, not a single cpu. How do I get "the cpu for which
__cpufreq_cooling_register() is called" if not by looping through all
the cpus in the mask?

> So, using that cpu *might* have worked here.
>
> Now the earlier loop you used was good to get this information,
> but it wasn't consistent and so I objected.
>
> What you should do:
>
> - Create another routine to find the cpu for which OPPs are bound
> to
> - And save the cpu_dev for it in the global struct for cpu_cooling

This I have done, it wasn't part of the snip that I sent.

> - reuse it wherever required.

Same as above.