linux-kernel - Re: [PATCH v3 5/7] cpufreq: add function to get the hardware max frequency

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Message-ID: <b63a4a47-99e5-9c71-73be-740aedde4714@arm.com>
Date:   Thu, 13 Feb 2020 11:59:56 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Ionela Voinescu <ionela.voinescu@....com>, catalin.marinas@....com,
        will@...nel.org, mark.rutland@....com, maz@...nel.org,
        suzuki.poulose@....com, sudeep.holla@....com, lukasz.luba@....com,
        rjw@...ysocki.net
Cc:     peterz@...radead.org, mingo@...hat.com, vincent.guittot@...aro.org,
        viresh.kumar@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v3 5/7] cpufreq: add function to get the hardware max
 frequency

On 2/11/20 6:45 PM, Ionela Voinescu wrote:
> +/**
> + * cpufreq_get_hw_max_freq - get the max hardware frequency of the CPU
> + * @cpu: CPU number
> + *
> + * The default return value is the max_freq field of cpuinfo.
> + */
> +__weak unsigned int cpufreq_get_hw_max_freq(unsigned int cpu)
> +{
> +	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> +	unsigned int ret_freq = 0;
> +
> +	if (policy) {
> +		ret_freq = policy->cpuinfo.max_freq;
> +		cpufreq_cpu_put(policy);

What about intel_pstate / turbo stuff? IIRC one of Giovanni's issues was that
turbo freq is not always reported as the max freq. Dunno if we can do
anything about it; at the very least maybe document the caveat?

> +	}
> +
> +	return ret_freq;
> +}
> +EXPORT_SYMBOL(cpufreq_get_hw_max_freq);
> +
>  static unsigned int __cpufreq_get(struct cpufreq_policy *policy)
>  {
>  	if (unlikely(policy_is_inactive(policy)))