linux-kernel - Re: [PATCH 1/8] cpufreq: allow drivers to flag custom support for freq invariance

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Message-ID: <20200701094417.ffuvduz6pqknjcks@vireshk-i7>
Date:   Wed, 1 Jul 2020 16:16:17 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ionela Voinescu <ionela.voinescu@....com>
Cc:     rjw@...ysocki.net, catalin.marinas@....com, sudeep.holla@....com,
        will@...nel.org, linux@...linux.org.uk, valentin.schneider@....com,
        mingo@...hat.com, peterz@...radead.org, dietmar.eggemann@....com,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] cpufreq: allow drivers to flag custom support for
 freq invariance

On 01-07-20, 10:07, Ionela Voinescu wrote:
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 3494f6763597..42668588f9f8 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -293,7 +293,7 @@ __ATTR(_name, 0644, show_##_name, store_##_name)
>  
>  struct cpufreq_driver {
>  	char		name[CPUFREQ_NAME_LEN];
> -	u8		flags;
> +	u16		flags;

Lets make it u32.

>  	void		*driver_data;
>  
>  	/* needed by all drivers */
> @@ -417,6 +417,14 @@ struct cpufreq_driver {
>   */
>  #define CPUFREQ_IS_COOLING_DEV			BIT(7)
>  
> +/*
> + * Set by drivers which implement the necessary calls to the scheduler's
> + * frequency invariance engine. The use of this flag will result in the
> + * default arch_set_freq_scale calls being skipped in favour of custom
> + * driver calls.
> + */
> +#define CPUFREQ_CUSTOM_SET_FREQ_SCALE		BIT(8)

I will rather suggest CPUFREQ_SKIP_SET_FREQ_SCALE as the name and
functionality. We need to give drivers a choice if they do not want
the core to do it on their behalf, because they are doing it on their
own or they don't want to do it.

-- 
viresh