Re: [PATCH v6 6/7][Resend] cpufreq: Support for fast frequency switching

[Steve Muckle]

Hi Rafael,

On 03/21/2016 06:53 PM, Rafael J. Wysocki wrote:
> Add two new policy flags, fast_switch_possible, to be set by the
> cpufreq driver if fast frequency switching can be used for the
> given policy and fast_switch_enabled, to be set by the governor
> if it is going to use fast frequency switching for the given
> policy.  Also add a helper for setting the latter.
...
> @@ -740,6 +777,9 @@ static int acpi_cpufreq_cpu_init(struct
>  		goto err_unreg;
>  	}
>  
> +	policy->fast_switch_possible = !acpi_pstate_strict &&
> +		!(policy_is_shared(policy) && policy->shared_type != CPUFREQ_SHARED_TYPE_ANY);

Could the policy->fast_switch_possible flag be avoided by just checking
whether a driver has registered the .fast_switch callback?

...
> @@ -1726,6 +1810,34 @@ EXPORT_SYMBOL(cpufreq_unregister_notifie
>   *                              GOVERNORS                            *
>   *********************************************************************/
>  
> +/**
> + * cpufreq_driver_fast_switch - Carry out a fast CPU frequency switch.
> + * @policy: cpufreq policy to switch the frequency for.
> + * @target_freq: New frequency to set (may be approximate).
> + *
> + * Carry out a fast frequency switch from interrupt context.

I think that should say atomic rather than interrupt as this might not
be called from interrupt context.

thanks,
Steve