RE: [PATCH v3 8/8] cpufreq: amd_pstate: add driver working mode status sysfs entry

[Yuan, Perry]

[AMD Official Use Only - General]

Hi Nathan. 

> -----Original Message-----
> From: Fontenot, Nathan <Nathan.Fontenot@xxxxxxx>
> Sent: Friday, November 11, 2022 12:07 AM
> To: Yuan, Perry <Perry.Yuan@xxxxxxx>; rafael.j.wysocki@xxxxxxxxx; Huang,
> Ray <Ray.Huang@xxxxxxx>; viresh.kumar@xxxxxxxxxx
> Cc: Sharma, Deepak <Deepak.Sharma@xxxxxxx>; Limonciello, Mario
> <Mario.Limonciello@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Huang, Shimmer
> <Shimmer.Huang@xxxxxxx>; Du, Xiaojian <Xiaojian.Du@xxxxxxx>; Meng,
> Li (Jassmine) <Li.Meng@xxxxxxx>; linux-pm@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v3 8/8] cpufreq: amd_pstate: add driver working mode
> status sysfs entry
> 
> On 11/7/22 11:57, Perry Yuan wrote:
> > While amd-pstate driver was loaded with specific driver mode, it will
> > need to check which mode is enabled for the pstate driver,add this
> > sysfs entry to show the current status
> >
> > $ cat /sys/devices/system/cpu/amd-pstate/status
> > active
> >
> > Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
> > ---
> >  drivers/cpufreq/amd-pstate.c | 44
> > ++++++++++++++++++++++++++++++++++++
> >  1 file changed, 44 insertions(+)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index 6958c5fd9e1c..eadcc9d61d39 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -65,6 +65,8 @@ static int disable_pstate_load __initdata;  static
> > int epp_off __initdata;
> >
> >  static struct cpufreq_driver *default_pstate_driver;
> > +static struct cpufreq_driver amd_pstate_epp_driver; static struct
> > +cpufreq_driver amd_pstate_driver;
> >  static struct amd_cpudata **all_cpu_data;
> >
> >  static struct amd_pstate_params global_params; @@ -819,6 +821,46 @@
> > static ssize_t store_pstate_dynamic_boost(struct kobject *a,
> >  	return count;
> >  }
> >
> > +static ssize_t amd_pstate_show_status(char *buf) {
> > +	if (!default_pstate_driver)
> > +		return sprintf(buf, "off\n");
> > +
> > +	return sprintf(buf, "%s\n", default_pstate_driver ==
> &amd_pstate_epp_driver ?
> > +					"active" : "passive");
> > +}
> > +
> > +static int amd_pstate_update_status(const char *buf, size_t size) {
> > +	/* FIXME: add driver dynamic switching code */
> > +	return 0;
> > +}
> > +
> > +static ssize_t show_status(struct kobject *kobj,
> > +			   struct kobj_attribute *attr, char *buf) {
> > +	ssize_t ret;
> > +
> > +	mutex_lock(&amd_pstate_driver_lock);
> > +	ret = amd_pstate_show_status(buf);
> > +	mutex_unlock(&amd_pstate_driver_lock);
> 
> Do we really need to take a lock to show the driver status?

Yes. 
It needs to check the current status from sysfs now  and  it will support to switch the EPP and Non EPP driver through this sysfs node.

Perry. 
> 
> -Nathan
> 
> > +
> > +	return ret;
> > +}
> > +
> > +static ssize_t store_status(struct kobject *a, struct kobj_attribute *b,
> > +			    const char *buf, size_t count) {
> > +	char *p = memchr(buf, '\n', count);
> > +	int ret;
> > +
> > +	mutex_lock(&amd_pstate_driver_lock);
> > +	ret = amd_pstate_update_status(buf, p ? p - buf : count);
> > +	mutex_unlock(&amd_pstate_driver_lock);
> > +
> > +	return ret < 0 ? ret : count;
> > +}
> > +
> >  cpufreq_freq_attr_ro(amd_pstate_max_freq);
> >  cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
> >
> > @@ -826,6 +868,7 @@ 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);
> > +define_one_global_rw(status);
> >
> >  static struct freq_attr *amd_pstate_attr[] = {
> >  	&amd_pstate_max_freq,
> > @@ -845,6 +888,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
> >
> >  static struct attribute *pstate_global_attributes[] = {
> >  	&pstate_dynamic_boost.attr,
> > +	&status.attr,
> >  	NULL
> >  };
> >