linux-kernel - Re: [PATCH v2 4/7] cpufreq: report whether cpufreq supports Frequency Invariance (FI)

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Message-ID: <20200730044346.rgtaikotkgwdpc3m@vireshk-mac-ubuntu>
Date:   Thu, 30 Jul 2020 10:13:46 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ionela Voinescu <ionela.voinescu@....com>
Cc:     rjw@...ysocki.net, dietmar.eggemann@....com,
        catalin.marinas@....com, sudeep.holla@....com, will@...nel.org,
        linux@...linux.org.uk, mingo@...hat.com, peterz@...radead.org,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/7] cpufreq: report whether cpufreq supports
 Frequency Invariance (FI)

On 22-07-20, 10:37, Ionela Voinescu wrote:
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 3497c1cd6818..1d0b046fe8e9 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -61,6 +61,9 @@ static struct cpufreq_driver *cpufreq_driver;
>  static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
>  static DEFINE_RWLOCK(cpufreq_driver_lock);
>  
> +/* Mark support for the scheduler's frequency invariance engine */
> +static DEFINE_STATIC_KEY_FALSE(cpufreq_set_freq_scale);
> +
>  /* Flag to suspend/resume CPUFreq governors */
>  static bool cpufreq_suspended;
>  
> @@ -69,6 +72,25 @@ static inline bool has_target(void)
>  	return cpufreq_driver->target_index || cpufreq_driver->target;
>  }
>  
> +static inline
> +void enable_cpufreq_freq_invariance(struct cpufreq_driver *driver)
> +{
> +	if ((driver->target || driver->target_index || driver->fast_switch) &&
> +	    !driver->setpolicy) {

Just checking for !driver->setpolicy should be enough here.

> +		static_branch_enable_cpuslocked(&cpufreq_set_freq_scale);
> +		pr_debug("%s: Driver %s can provide frequency invariance.",
> +			 __func__, driver->name);

I think a simpler print will work well too.

                pr_debug("Freq invariance enabled");

__func__ isn't really required as this is the only print with that
kind of info in cpufreq.c.

> +	} else
> +		pr_err("%s: Driver %s cannot provide frequency invariance.",
> +		__func__, driver->name);

Why not supporting freq-invariance an error ? I will just drop this
message completely.

-- 
viresh