Re: [PATCH] arch_topology: Update user supplied capacity to possible cpus in cluster

[Quentin Perret <quentin.perret@arm.com>]

On Tuesday 05 Mar 2019 at 11:13:21 (+0000), Sudeep Holla wrote:
[...]
> While I like the idea, I am afraid that linking this to cpufreq policy
> may not be good. How will we deal with it on systems without CPUfreq ?

Maybe something like this ?

	policy = cpufreq_cpu_get(cpu);
	if (policy) {
		for_each_cpu(i, policy->related_cpus) {
			/* Update capacity for @i*/
		}
		cpufreq_cpu_put(policy);
	} else {
		/* Update capacity for @cpu*/
	}

I think it's OK to assume per-cpu capacities w/o CPUFreq. The only
case where it makes sense to 'bind' the capacity of several CPUs
together is when they're part of the same perf domain, I think. If you
don't know what the perf domains are, then there's nothing sensible you
can do.

And for the dependency, a large part of the arch_topology driver is
already dependent on CPUFreq -- it registers a CPUFreq notifier on boot
to re-scale the CPU capacities depending on the max freq of the various
policies and so on. So the dependency is already there somehow.

[...]

> I think if there are no valid users of this, we *must* remove it. As I
> have pointed out in past, giving user such access will need platform
> knowledge. Though it's debatable topic, firmware providing this
> information is the only correct solution IMO.

Yeah, if nobody is using it then maybe we can just remove it. Or at
least we can give it a go and if somebody complains then we can 'fix' it
with something like my snippet above :-)

Thanks,
Quentin

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