linux-kernel - Re: [PATCH 13/19] cpupower: add the function to check amd-pstate enabled

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Message-ID: <20210913112945.GE3731830@hr-amd>
Date:   Mon, 13 Sep 2021 19:29:45 +0800
From:   Huang Rui <ray.huang@....com>
To:     Shuah Khan <skhan@...uxfoundation.org>
CC:     "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Borislav Petkov <bp@...e.de>, Ingo Molnar <mingo@...nel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "Sharma, Deepak" <Deepak.Sharma@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Limonciello, Mario" <Mario.Limonciello@....com>,
        "Fontenot, Nathan" <Nathan.Fontenot@....com>,
        "Su, Jinzhou (Joe)" <Jinzhou.Su@....com>,
        "Du, Xiaojian" <Xiaojian.Du@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH 13/19] cpupower: add the function to check amd-pstate
 enabled

On Fri, Sep 10, 2021 at 06:16:21AM +0800, Shuah Khan wrote:
> On 9/8/21 8:59 AM, Huang Rui wrote:
> > Introduce the cpupower_amd_pstate_enabled() to check whether the kernel
> > mode enables amd-pstate.
> > 
> 
> What does "kernel mode" mean? Are you referring to kernel vs.
> firmware mode?

I am referring kernel. In fact, the proccessor which supports the AMD
P-States also supports the legacy ACPI P-States as well. So this API is to
check whether the kernel driver is using amd-pstate or acpi-cpufreq.

I would have explained this, sorry to make you confused, I will explain the
details in the commit log at V2.

Thanks,
Ray

> 
> > Signed-off-by: Huang Rui <ray.huang@....com>
> > ---
> >   tools/power/cpupower/utils/helpers/helpers.h |  5 +++++
> >   tools/power/cpupower/utils/helpers/misc.c    | 20 ++++++++++++++++++++
> >   2 files changed, 25 insertions(+)
> > 
> > diff --git a/tools/power/cpupower/utils/helpers/helpers.h b/tools/power/cpupower/utils/helpers/helpers.h
> > index b4813efdfb00..eb43c14d1728 100644
> > --- a/tools/power/cpupower/utils/helpers/helpers.h
> > +++ b/tools/power/cpupower/utils/helpers/helpers.h
> > @@ -136,6 +136,11 @@ extern int decode_pstates(unsigned int cpu, int boost_states,
> >   
> >   extern int cpufreq_has_boost_support(unsigned int cpu, int *support,
> >   				     int *active, int * states);
> > +
> > +/* AMD PSTATE enabling **************************/
> > +
> > +extern unsigned long cpupower_amd_pstate_enabled(unsigned int cpu);
> > +
> >   /*
> >    * CPUID functions returning a single datum
> >    */
> > diff --git a/tools/power/cpupower/utils/helpers/misc.c b/tools/power/cpupower/utils/helpers/misc.c
> > index fc6e34511721..07d80775fb68 100644
> > --- a/tools/power/cpupower/utils/helpers/misc.c
> > +++ b/tools/power/cpupower/utils/helpers/misc.c
> > @@ -83,6 +83,26 @@ int cpupower_intel_set_perf_bias(unsigned int cpu, unsigned int val)
> >   	return 0;
> >   }
> >   
> > +unsigned long cpupower_amd_pstate_enabled(unsigned int cpu)
> > +{
> > +	char linebuf[MAX_LINE_LEN];
> > +	char path[SYSFS_PATH_MAX];
> > +	unsigned long val;
> > +	char *endp;
> > +
> > +	snprintf(path, sizeof(path),
> > +		 PATH_TO_CPU "cpu%u/cpufreq/is_amd_pstate_enabled", cpu);
> > +
> > +	if (cpupower_read_sysfs(path, linebuf, MAX_LINE_LEN) == 0)
> > +		return 0;
> > +
> > +	val = strtoul(linebuf, &endp, 0);
> > +	if (endp == linebuf || errno == ERANGE)
> > +		return 0;
> > +
> > +	return val;
> > +}
> > +
> >   #endif /* #if defined(__i386__) || defined(__x86_64__) */
> >   
> >   /* get_cpustate
> > 
>