Re: [PATCH] cpufreq: use last policy after online

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Tuesday, December 01, 2015 04:52:14 PM Srinivas Pandruvada wrote:
> For cpufreq drivers which use setpolicy interface, after offline->online
> the policy is set to default. This can be reproduced by setting the
> default policy of intel_pstate or longrun to ondemand and then change to
> "performance". After offline and online, the setpolicy will be called with
> the policy=ondemand.
> For drivers using governors this condition is handled by storing
> last_governor, during offline and restoring during online. The same should
> be done for drivers using setpolicy interface. Storing last_policy during
> offline and restoring during online.
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>

I guess this is urgent, right?

Is it a regression fix or has it just never worked?

> ---
>  drivers/cpufreq/cpufreq.c | 14 ++++++++++----
>  include/linux/cpufreq.h   |  1 +
>  2 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index a83c995..8412ce5 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -976,10 +976,14 @@ static int cpufreq_init_policy(struct cpufreq_policy *policy)
>  
>  	new_policy.governor = gov;
>  
> -	/* Use the default policy if its valid. */
> -	if (cpufreq_driver->setpolicy)
> -		cpufreq_parse_governor(gov->name, &new_policy.policy, NULL);
> -
> +	/* Use the default policy if there is no last_policy. */
> +	if (cpufreq_driver->setpolicy) {
> +		if (policy->last_policy)
> +			new_policy.policy = policy->last_policy;
> +		else
> +			cpufreq_parse_governor(gov->name, &new_policy.policy,
> +					       NULL);
> +	}
>  	/* set default policy */
>  	return cpufreq_set_policy(policy, &new_policy);
>  }
> @@ -1330,6 +1334,8 @@ static void cpufreq_offline_prepare(unsigned int cpu)
>  		if (has_target())
>  			strncpy(policy->last_governor, policy->governor->name,
>  				CPUFREQ_NAME_LEN);
> +		else
> +			policy->last_policy = policy->policy;
>  	} else if (cpu == policy->cpu) {
>  		/* Nominate new CPU */
>  		policy->cpu = cpumask_any(policy->cpus);
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index ef4c5b1..177c768 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -77,6 +77,7 @@ struct cpufreq_policy {
>  	unsigned int		suspend_freq; /* freq to set during suspend */
>  
>  	unsigned int		policy; /* see above */
> +	unsigned int		last_policy; /* policy before unplug */
>  	struct cpufreq_governor	*governor; /* see below */
>  	void			*governor_data;
>  	bool			governor_enabled; /* governor start/stop flag */
> 

Thanks,
Rafael