linux-kernel - Re: [PATCH v3 7/8] cpufreq: amd-pstate: add frequency dynamic boost sysfs control

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Date:   Mon, 7 Nov 2022 13:09:41 -0600
From:   "Limonciello, Mario" <mario.limonciello@....com>
To:     Perry Yuan <Perry.Yuan@....com>, rafael.j.wysocki@...el.com,
        ray.huang@....com, viresh.kumar@...aro.org
Cc:     Deepak.Sharma@....com, Nathan.Fontenot@....com,
        Alexander.Deucher@....com, Shimmer.Huang@....com,
        Xiaojian.Du@....com, Li.Meng@....com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, wyes.karny@....com
Subject: Re: [PATCH v3 7/8] cpufreq: amd-pstate: add frequency dynamic boost
 sysfs control

On 11/7/2022 12:16, Limonciello, Mario wrote:
> +wyes.karny@....com
> 
> On 11/7/2022 11:57, Perry Yuan wrote:
>> Add one sysfs entry to control the CPU cores frequency boost state
>> The attribute file can allow user to set max performance boosted or
>> keeping at normal perf level.
>>
>> Signed-off-by: Perry Yuan <Perry.Yuan@....com>
>> ---
>>   drivers/cpufreq/amd-pstate.c | 53 ++++++++++++++++++++++++++++++++++++
>>   1 file changed, 53 insertions(+)
> 
> Make sure that you update the documentation for this new sysfs file as 
> well.
> 
>>
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index 841b1e2383b8..6958c5fd9e1c 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -786,12 +786,46 @@ static ssize_t show_energy_performance_preference(
>>           return  sprintf(buf, "%s\n", energy_perf_strings[preference]);
>>   }
>> +static void amd_pstate_update_policies(void)
>> +{
>> +    int cpu;
>> +
>> +    for_each_possible_cpu(cpu)
>> +        cpufreq_update_policy(cpu);
>> +}
>> +
>> +static ssize_t show_pstate_dynamic_boost(struct kobject *kobj,
>> +                struct kobj_attribute *attr, char *buf)
>> +{
>> +    return sprintf(buf, "%u\n", cppc_boost);
>> +}
>> +
>> +static ssize_t store_pstate_dynamic_boost(struct kobject *a,
>> +                       struct kobj_attribute *b,
>> +                       const char *buf, size_t count)
>> +{
>> +    unsigned int input;
>> +    int ret;
>> +
>> +    ret = kstrtouint(buf, 10, &input);
>> +    if (ret)
>> +        return ret;
> 
> To be more flexible maybe kstrtobool would be better here instead?
> 
>> +
>> +    mutex_lock(&amd_pstate_driver_lock);
>> +    cppc_boost = !!input;
>> +    amd_pstate_update_policies();
>> +    mutex_unlock(&amd_pstate_driver_lock);
>> +
>> +    return count;
>> +}
>> +
>>   cpufreq_freq_attr_ro(amd_pstate_max_freq);
>>   cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
>>   cpufreq_freq_attr_ro(amd_pstate_highest_perf);
>>   cpufreq_freq_attr_rw(energy_performance_preference);
>>   cpufreq_freq_attr_ro(energy_performance_available_preferences);
>> +define_one_global_rw(pstate_dynamic_boost);
>>   static struct freq_attr *amd_pstate_attr[] = {
>>       &amd_pstate_max_freq,
>> @@ -809,6 +843,15 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
>>       NULL,
>>   };
>> +static struct attribute *pstate_global_attributes[] = {
>> +    &pstate_dynamic_boost.attr,
>> +    NULL
>> +};
>> +
>> +static const struct attribute_group amd_pstate_global_attr_group = {
>> +    .attrs = pstate_global_attributes,
>> +};
>> +
>>   static inline void update_boost_state(void)
>>   {
>>       u64 misc_en;
>> @@ -1416,6 +1459,16 @@ static int __init amd_pstate_init(void)
>>           pr_err("failed to register amd pstate driver with return %d\n",
>>                  ret);
>> +    amd_pstate_kobj = kobject_create_and_add("amd-pstate", 
>> &cpu_subsys.dev_root->kobj);
>> +    if (!amd_pstate_kobj)
>> +        pr_err("amd-pstate: Global sysfs registration failed.\n");
>> +
>> +    ret = sysfs_create_group(amd_pstate_kobj, 
>> &amd_pstate_global_attr_group);
>> +    if (ret) {
>> +        pr_err("amd-pstate: Sysfs attribute export failed with error 
>> %d.\n",
>> +               ret);
> 
> amd-pstate can currently be a module too.  So don't you need the 
> matching cleanup path for this code too?

I noticed your patch 3/8 makes this change, so this specific comment 
might not be as important anymore.

> 
> Also, regarding the error messages you don't need to prefix with 
> "amd-pstate: ", amd-pstate.c already sets `pr_fmt`.

Also, shouldn't failing to make these attributes fail the rest of 
amd-pstate init rather than just showing error messages?

> 
>> +    }
>> +
>>       return ret;
>>   }
>>   device_initcall(amd_pstate_init);
>