Messages in this thread | | | Date | Thu, 18 Feb 2021 16:36:35 +0000 | From | Ionela Voinescu <> | Subject | Re: [PATCH V3 1/2] topology: Allow multiple entities to provide sched_freq_tick() callback |
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Hey,
On Thursday 18 Feb 2021 at 15:03:04 (+0530), Viresh Kumar wrote: > On 17-02-21, 00:24, Ionela Voinescu wrote: > > > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c > > > index 1e47dfd465f8..47fca7376c93 100644 > > > --- a/arch/arm64/kernel/topology.c > > > +++ b/arch/arm64/kernel/topology.c > > > @@ -240,7 +240,6 @@ static struct scale_freq_data amu_sfd = { > > > > > > static void amu_fie_setup(const struct cpumask *cpus) > > > { > > > - bool invariant; > > > int cpu; > > > > > > /* We are already set since the last insmod of cpufreq driver */ > > > @@ -257,25 +256,10 @@ static void amu_fie_setup(const struct cpumask *cpus) > > > > > > cpumask_or(amu_fie_cpus, amu_fie_cpus, cpus); > > > > > > - invariant = topology_scale_freq_invariant(); > > > - > > > - /* We aren't fully invariant yet */ > > > - if (!invariant && !cpumask_equal(amu_fie_cpus, cpu_present_mask)) > > > - return; > > > - > > > > You still need these checks, otherwise you could end up with only part > > of the CPUs setting a scale factor, when only part of the CPUs support > > AMUs and there is no cpufreq support for FIE. > > Another look at it and here goes another reason (hope I don't have > another in-code comment somewhere else to kill this one) :) > > We don't need to care for the reason you gave (which is a valid reason > otherwise), as we are talking specifically about amu_fie_setup() here > and it gets called from cpufreq policy-notifier. i.e. we won't support > AMUs without cpufreq being there in the first place and the same goes > for cppc-driver. > > Does that sound reasonable ? >
Yes, we don't care if there is no cpufreq driver, as the use of AMUs won't get initialised either. But we do care if there is a cpufreq driver that does not support frequency invariance, which is the example above.
The intention with the patches that made cpufreq based invariance generic a while back was for it to be present, seamlessly, for as many drivers as possible, as a less than accurate invariance default method is still better than nothing. So only a few drivers today don't support cpufreq based FI, but it's not a guarantee that it will stay this way.
Hope it makes sense, Ionela.
> -- > viresh
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