cpufreq: Introduce a more generic way to boost when cpu is going online

[PATCH 2/2] cpufreq: Introduce a more generic way to set default per-policy boost flag

Posted by Lifeng Zheng 3 weeks ago

In cpufreq_online() of cpufreq.c, the per-policy boost flag is already set
to mirror the cpufreq_driver boost during init but using freq_table to
judge if the policy has boost frequency. There are two drawbacks to this
approach:

1. It doesn't work for the cpufreq drivers that do not use a frequency
table. For now, acpi-cpufreq and amd-pstate have to enable boost in policy
initialization. And cppc_cpufreq never set policy to boost when going
online no matter what the cpufreq_driver boost flag is.

2. If the cpu goes offline when cpufreq_driver boost enabled and then goes
online when cpufreq_driver boost disabled, the per-policy boost flag will
unreasonably remain true.

Running set_boost at the end of the online process is a more generic way
for all cpufreq drivers.

Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
---
 drivers/cpufreq/cpufreq.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 03ae879d50b9..867bda3decfd 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1409,10 +1409,6 @@ static int cpufreq_online(unsigned int cpu)
 			goto out_free_policy;
 		}
 
-		/* Let the per-policy boost flag mirror the cpufreq_driver boost during init */
-		if (cpufreq_boost_enabled() && policy_has_boost_freq(policy))
-			policy->boost_enabled = true;
-
 		/*
 		 * The initialization has succeeded and the policy is online.
 		 * If there is a problem with its frequency table, take it
@@ -1576,6 +1572,18 @@ static int cpufreq_online(unsigned int cpu)
 	if (new_policy && cpufreq_thermal_control_enabled(cpufreq_driver))
 		policy->cdev = of_cpufreq_cooling_register(policy);
 
+	/* Let the per-policy boost flag mirror the cpufreq_driver boost during init */
+	if (cpufreq_boost_supported()) {
+		policy->boost_enabled = cpufreq_boost_enabled();
+		ret = cpufreq_driver->set_boost(policy, policy->boost_enabled);
+		if (ret) {
+			/* If the set_boost fails, the online operation is not affected */
+			pr_info("%s: CPU%d: Cannot %s BOOST\n", __func__, policy->cpu,
+				policy->boost_enabled ? "enable" : "disable");
+			policy->boost_enabled = !policy->boost_enabled;
+		}
+	}
+
 	pr_debug("initialization complete\n");
 
 	return 0;
-- 
2.33.0

Re: [PATCH 2/2] cpufreq: Introduce a more generic way to set default per-policy boost flag

Posted by Viresh Kumar 2 weeks, 6 days ago

On 15-01-25, 18:01, Lifeng Zheng wrote:
> In cpufreq_online() of cpufreq.c, the per-policy boost flag is already set
> to mirror the cpufreq_driver boost during init but using freq_table to
> judge if the policy has boost frequency. There are two drawbacks to this
> approach:
> 
> 1. It doesn't work for the cpufreq drivers that do not use a frequency
> table. For now, acpi-cpufreq and amd-pstate have to enable boost in policy
> initialization. And cppc_cpufreq never set policy to boost when going
> online no matter what the cpufreq_driver boost flag is.
> 
> 2. If the cpu goes offline when cpufreq_driver boost enabled and then goes
> online when cpufreq_driver boost disabled, the per-policy boost flag will
> unreasonably remain true.

Yeah, this is a problem. I agree. If the global boost is disabled,
then boost shouldn't be allowed for any of the policies.

> Running set_boost at the end of the online process is a more generic way
> for all cpufreq drivers.
> 
> Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
> ---
>  drivers/cpufreq/cpufreq.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 03ae879d50b9..867bda3decfd 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1409,10 +1409,6 @@ static int cpufreq_online(unsigned int cpu)
>  			goto out_free_policy;
>  		}
>  
> -		/* Let the per-policy boost flag mirror the cpufreq_driver boost during init */
> -		if (cpufreq_boost_enabled() && policy_has_boost_freq(policy))
> -			policy->boost_enabled = true;
> -
>  		/*
>  		 * The initialization has succeeded and the policy is online.
>  		 * If there is a problem with its frequency table, take it
> @@ -1576,6 +1572,18 @@ static int cpufreq_online(unsigned int cpu)
>  	if (new_policy && cpufreq_thermal_control_enabled(cpufreq_driver))
>  		policy->cdev = of_cpufreq_cooling_register(policy);
>  
> +	/* Let the per-policy boost flag mirror the cpufreq_driver boost during init */
> +	if (cpufreq_boost_supported()) {
> +		policy->boost_enabled = cpufreq_boost_enabled();
> +		ret = cpufreq_driver->set_boost(policy, policy->boost_enabled);

Maybe we can optimize here and not call set_boost() if policy's
boost_enabled is not changing at all.
        if (policy->boost_enabled != cpufreq_boost_enabled()) {
                policy->boost_enabled = cpufreq_boost_enabled();
                ret = cpufreq_driver->set_boost(policy, policy->boost_enabled);
                ...
        }

After this patch, maybe you should simplify the drivers as well, which
take care of enabling/boost at boot time or setting this flag ?

> +		if (ret) {
> +			/* If the set_boost fails, the online operation is not affected */
> +			pr_info("%s: CPU%d: Cannot %s BOOST\n", __func__, policy->cpu,
> +				policy->boost_enabled ? "enable" : "disable");
> +			policy->boost_enabled = !policy->boost_enabled;
> +		}
> +	}
> +
>  	pr_debug("initialization complete\n");
>  
>  	return 0;

-- 
viresh

Re: [PATCH 2/2] cpufreq: Introduce a more generic way to set default per-policy boost flag

Posted by zhenglifeng (A) 2 weeks, 6 days ago

On 2025/1/16 14:54, Viresh Kumar wrote:

> On 15-01-25, 18:01, Lifeng Zheng wrote:
>> In cpufreq_online() of cpufreq.c, the per-policy boost flag is already set
>> to mirror the cpufreq_driver boost during init but using freq_table to
>> judge if the policy has boost frequency. There are two drawbacks to this
>> approach:
>>
>> 1. It doesn't work for the cpufreq drivers that do not use a frequency
>> table. For now, acpi-cpufreq and amd-pstate have to enable boost in policy
>> initialization. And cppc_cpufreq never set policy to boost when going
>> online no matter what the cpufreq_driver boost flag is.
>>
>> 2. If the cpu goes offline when cpufreq_driver boost enabled and then goes
>> online when cpufreq_driver boost disabled, the per-policy boost flag will
>> unreasonably remain true.
> 
> Yeah, this is a problem. I agree. If the global boost is disabled,
> then boost shouldn't be allowed for any of the policies.
> 
>> Running set_boost at the end of the online process is a more generic way
>> for all cpufreq drivers.
>>
>> Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
>> ---
>>  drivers/cpufreq/cpufreq.c | 16 ++++++++++++----
>>  1 file changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index 03ae879d50b9..867bda3decfd 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -1409,10 +1409,6 @@ static int cpufreq_online(unsigned int cpu)
>>  			goto out_free_policy;
>>  		}
>>  
>> -		/* Let the per-policy boost flag mirror the cpufreq_driver boost during init */
>> -		if (cpufreq_boost_enabled() && policy_has_boost_freq(policy))
>> -			policy->boost_enabled = true;
>> -
>>  		/*
>>  		 * The initialization has succeeded and the policy is online.
>>  		 * If there is a problem with its frequency table, take it
>> @@ -1576,6 +1572,18 @@ static int cpufreq_online(unsigned int cpu)
>>  	if (new_policy && cpufreq_thermal_control_enabled(cpufreq_driver))
>>  		policy->cdev = of_cpufreq_cooling_register(policy);
>>  
>> +	/* Let the per-policy boost flag mirror the cpufreq_driver boost during init */
>> +	if (cpufreq_boost_supported()) {
>> +		policy->boost_enabled = cpufreq_boost_enabled();
>> +		ret = cpufreq_driver->set_boost(policy, policy->boost_enabled);
> 
> Maybe we can optimize here and not call set_boost() if policy's
> boost_enabled is not changing at all.
>         if (policy->boost_enabled != cpufreq_boost_enabled()) {
>                 policy->boost_enabled = cpufreq_boost_enabled();
>                 ret = cpufreq_driver->set_boost(policy, policy->boost_enabled);
>                 ...
>         }

Makes sense. Thanks.

> 
> After this patch, maybe you should simplify the drivers as well, which
> take care of enabling/boost at boot time or setting this flag ?

OK. I'll try to.

> 
>> +		if (ret) {
>> +			/* If the set_boost fails, the online operation is not affected */
>> +			pr_info("%s: CPU%d: Cannot %s BOOST\n", __func__, policy->cpu,
>> +				policy->boost_enabled ? "enable" : "disable");
>> +			policy->boost_enabled = !policy->boost_enabled;
>> +		}
>> +	}
>> +
>>  	pr_debug("initialization complete\n");
>>  
>>  	return 0;
>

[PATCH 1/2] cpufreq: Fix re-boost issue after hotplugging a cpu
[PATCH 2/2] cpufreq: Introduce a more generic way to set default per-policy boost flag