linux-kernel - Re: [RFC PATCH] cpufreq: userspace: Add fast-switch support for userspace

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Message-ID: <09acd46b-ec63-46ec-a239-e792c3061e52@arm.com>
Date: Mon, 9 Dec 2024 10:36:27 +0000
From: Christian Loehle <christian.loehle@....com>
To: Xuewen Yan <xuewen.yan@...soc.com>, rafael@...nel.org,
 viresh.kumar@...aro.org, linux-pm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, guohua.yan@...soc.com, ke.wang@...soc.com,
 xuewen.yan94@...il.com
Subject: Re: [RFC PATCH] cpufreq: userspace: Add fast-switch support for
 userspace

On 12/9/24 08:14, Xuewen Yan wrote:
> Now, the userspace governor does not support userspace,
> if the driver only use the fast-switch and not add target_index(),

Which driver does that? Is that actually valid?
No mainline driver from what I can see.

> it will cause uerspace not work.

s/uerspace/userspace
to not work?

> So add fast-switch support for userspace governor.
> 
> Co-developed-by: Guohua Yan <guohua.yan@...soc.com>
> Signed-off-by: Guohua Yan <guohua.yan@...soc.com>
> Signed-off-by: Xuewen Yan <xuewen.yan@...soc.com>
> ---
>  drivers/cpufreq/cpufreq_userspace.c | 35 +++++++++++++++++++++++++----
>  1 file changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq_userspace.c b/drivers/cpufreq/cpufreq_userspace.c
> index 2c42fee76daa..3a99197246ed 100644
> --- a/drivers/cpufreq/cpufreq_userspace.c
> +++ b/drivers/cpufreq/cpufreq_userspace.c
> @@ -21,6 +21,30 @@ struct userspace_policy {
>  	struct mutex mutex;
>  };
>  
> +static int cpufreq_userspace_target_freq(struct cpufreq_policy *policy,
> +			unsigned int target_freq, unsigned int relation)
> +{
> +	int ret;

not really necessary

> +
> +	if (policy->fast_switch_enabled) {
> +		unsigned int idx;
> +
> +		target_freq = clamp_val(target_freq, policy->min, policy->max);
> +
> +		if (!policy->freq_table)
> +			return target_freq;
> +
> +		idx = cpufreq_frequency_table_target(policy, target_freq, relation);
> +		policy->cached_resolved_idx = idx;
> +		policy->cached_target_freq = target_freq;
> +		ret = !cpufreq_driver_fast_switch(policy, policy->freq_table[idx].frequency);
> +	} else {
> +		ret = __cpufreq_driver_target(policy, target_freq, relation);

NIT: could save the indent if you reverse conditions and ret early on !fast_switch

> +	}
> +
> +	return ret;
> +}
> +
>  /**
>   * cpufreq_set - set the CPU frequency
>   * @policy: pointer to policy struct where freq is being set
> @@ -41,7 +65,7 @@ static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
>  
>  	userspace->setspeed = freq;
>  
> -	ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
> +	ret = cpufreq_userspace_target_freq(policy, freq, CPUFREQ_RELATION_L);
>   err:
>  	mutex_unlock(&userspace->mutex);
>  	return ret;
> @@ -62,6 +86,8 @@ static int cpufreq_userspace_policy_init(struct cpufreq_policy *policy)
>  
>  	mutex_init(&userspace->mutex);
>  
> +	cpufreq_enable_fast_switch(policy);
> +
>  	policy->governor_data = userspace;
>  	return 0;
>  }
> @@ -72,6 +98,7 @@ static int cpufreq_userspace_policy_init(struct cpufreq_policy *policy)
>   */
>  static void cpufreq_userspace_policy_exit(struct cpufreq_policy *policy)
>  {
> +	cpufreq_disable_fast_switch(policy);
>  	kfree(policy->governor_data);
>  	policy->governor_data = NULL;
>  }
> @@ -112,13 +139,13 @@ static void cpufreq_userspace_policy_limits(struct cpufreq_policy *policy)
>  		 policy->cpu, policy->min, policy->max, policy->cur, userspace->setspeed);
>  
>  	if (policy->max < userspace->setspeed)
> -		__cpufreq_driver_target(policy, policy->max,
> +		cpufreq_userspace_target_freq(policy, policy->max,
>  					CPUFREQ_RELATION_H);
>  	else if (policy->min > userspace->setspeed)
> -		__cpufreq_driver_target(policy, policy->min,
> +		cpufreq_userspace_target_freq(policy, policy->min,
>  					CPUFREQ_RELATION_L);
>  	else
> -		__cpufreq_driver_target(policy, userspace->setspeed,
> +		cpufreq_userspace_target_freq(policy, userspace->setspeed,
>  					CPUFREQ_RELATION_L);
>  
>  	mutex_unlock(&userspace->mutex);