linux-kernel - Re: [PATCH 4/4] arm64: implement CPPC FFH support using AMUs

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Message-ID: <20200911144032.GC12835@gaia>
Date:   Fri, 11 Sep 2020 15:40:32 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Ionela Voinescu <ionela.voinescu@....com>
Cc:     will@...nel.org, sudeep.holla@....com, morten.rasmussen@....com,
        valentin.schneider@....com, souvik.chakravarty@....com,
        viresh.kumar@...aro.org, dietmar.eggemann@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] arm64: implement CPPC FFH support using AMUs

On Wed, Aug 26, 2020 at 02:03:09PM +0100, Ionela Voinescu wrote:
> +/*
> + * Refer to drivers/acpi/cppc_acpi.c for the description of the functions
> + * below.
> + */
> +bool cpc_ffh_supported(void)
> +{
> +	const struct cpumask *cnt_cpu_mask = cpus_with_amu_counters();
> +	int cpu = nr_cpu_ids;
> +
> +	if (cnt_cpu_mask)
> +		cpu = cpumask_any_and(cnt_cpu_mask, cpu_present_mask);
> +
> +	if ((cpu >= nr_cpu_ids) || !freq_counters_valid(cpu))
> +		return false;
> +
> +	return true;
> +}

IIUC, the only need for the cpumask is this function, the others would
have worked just fine with the existing cpu_has_amu_feat(). So you have
a lot more !cnt_cpu_mask checks now.

I wonder whether instead you could add a new function near
cpu_has_amu_feat(), something like get_cpu_with_amu_feat() and do the
cpumask_any_and() in there.

-- 
Catalin