linux-kernel - Re: [PATCH] arm64: topology: Cleanup init_amu

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Message-ID: <20201210103446.r5tlgoptc7n4r33z@vireshk-i7>
Date:   Thu, 10 Dec 2020 16:04:46 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ionela Voinescu <ionela.voinescu@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: topology: Cleanup init_amu_fie() a bit

On 10-12-20, 12:48, Viresh Kumar wrote:
> Every time I have stumbled upon this routine, I get confused with the
> way 'have_policy' is used and I have to dig in to understand why is it
> so.
> 
> Here is an attempt to make it easier to understand, and hopefully it is
> an improvement. This is based on the logic that amu_fie_cpus will be
> empty if cpufreq policy wasn't available for any CPU.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
> 
> Ionela, I think it would be even better to do this over this patch
> 
> -       /*
> -        * If none of the CPUs have cpufreq support, we only enable
> -        * the use of the AMU feature for FIE if all CPUs support AMU.
> -        * Otherwise, enable_policy_freq_counters has already enabled
> -        * policy cpus.
> -        */
> -       if (cpumask_empty(amu_fie_cpus) &&
> -           cpumask_equal(valid_cpus, cpu_present_mask))
> +       /* Overwrite amu_fie_cpus if all CPUs support AMU */
> +       if (cpumask_equal(valid_cpus, cpu_present_mask))
>                 cpumask_copy(amu_fie_cpus, cpu_present_mask);
> 
> This will also take care of the case where the cpufreq policy isn't
> there for a small group of CPUs, which do have AMUs enabled for them.
> (This doesn't normally happen though).

And on similar lines, this change as well as amu_fie_cpus must be set
to all the CPUs and this check (and parameter to the routine) aren't
required..

 bool arch_freq_counters_available(const struct cpumask *cpus)
 {
-       return amu_freq_invariant() &&
-              cpumask_subset(cpus, amu_fie_cpus);
+       return amu_freq_invariant();
 }

-- 
viresh