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

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Message-ID: <1b7a5cd5-6ecf-8529-f10b-4f7f06fc7462@amd.com>
Date:   Mon, 7 Nov 2022 12:16:00 -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

+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?

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

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