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

[Limonciello, Mario]

On 11/7/2022 12:16, Limonciello, Mario wrote:
> +wyes.karny@xxxxxxx
>
> 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@xxxxxxx>
> > ---
> >   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);