linux-kernel - Re: [PATCH v3 18/21] cpupower: enable boost state support for amd-pstate module

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Date:   Wed, 3 Nov 2021 15:04:08 +0800
From:   Huang Rui <ray.huang@....com>
To:     "Fontenot, Nathan" <Nathan.Fontenot@....com>
Cc:     "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        "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>,
        Steven Noonan <steven@...vesoftware.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 v3 18/21] cpupower: enable boost state support for
 amd-pstate module

On Wed, Nov 03, 2021 at 04:11:09AM +0800, Fontenot, Nathan wrote:
> 
> 
> On 10/29/21 8:02 AM, Huang Rui wrote:
> > The legacy ACPI hardware P-States function has 3 P-States on ACPI table,
> > the CPU frequency only can be switched between the 3 P-States. While the
> > processor supports the boost state, it will have another boost state
> > that the frequency can be higher than P0 state, and the state can be
> > decoded by the function of decode_pstates() and read by
> > amd_pci_get_num_boost_states().
> > 
> > However, the new AMD P-States function is different than legacy ACPI
> > hardware P-State on AMD processors. That has a finer grain frequency
> > range between the highest and lowest frequency. And boost frequency is
> > actually the frequency which is mapped on highest performance ratio. The
> > similiar previous P0 frequency is mapped on nominal performance ratio.
> 
> s/similiar/similar/
> 
> > If the highest performance on the processor is higher than nominal
> > performance, then we think the current processor supports the boost
> > state. And it uses amd_pstate_boost_init() to initialize boost for AMD
> > P-States function.
> > 
> > Signed-off-by: Huang Rui <ray.huang@....com>
> > ---
> >  tools/power/cpupower/utils/helpers/amd.c     | 18 ++++++++++++++++++
> >  tools/power/cpupower/utils/helpers/helpers.h |  5 +++++
> >  tools/power/cpupower/utils/helpers/misc.c    |  2 ++
> >  3 files changed, 25 insertions(+)
> > 
> > diff --git a/tools/power/cpupower/utils/helpers/amd.c b/tools/power/cpupower/utils/helpers/amd.c
> > index f233a6ab75ac..92b9fb631768 100644
> > --- a/tools/power/cpupower/utils/helpers/amd.c
> > +++ b/tools/power/cpupower/utils/helpers/amd.c
> > @@ -182,5 +182,23 @@ static unsigned long amd_pstate_get_data(unsigned int cpu,
> >  						  MAX_AMD_PSTATE_VALUE_READ_FILES);
> >  }
> >  
> > +void amd_pstate_boost_init(unsigned int cpu, int *support, int *active)
> > +{
> > +	unsigned long highest_perf, nominal_perf, cpuinfo_min,
> > +		      cpuinfo_max, amd_pstate_max;
> > +
> > +	highest_perf = amd_pstate_get_data(cpu, AMD_PSTATE_HIGHEST_PERF);
> > +	nominal_perf = amd_pstate_get_data(cpu, AMD_PSTATE_NOMINAL_PERF);
> > +
> > +	*support = highest_perf > nominal_perf ? 1 : 0;
> > +	if (!(*support))
> > +		return;
> > +
> > +	cpufreq_get_hardware_limits(cpu, &cpuinfo_min, &cpuinfo_max);
> > +	amd_pstate_max = amd_pstate_get_data(cpu, AMD_PSTATE_MAX_FREQ);
> > +
> > +	*active = cpuinfo_max == amd_pstate_max ? 1 : 0;
> > +}
> > +
> >  /* AMD P-States Helper Functions ***************/
> >  #endif /* defined(__i386__) || defined(__x86_64__) */
> > diff --git a/tools/power/cpupower/utils/helpers/helpers.h b/tools/power/cpupower/utils/helpers/helpers.h
> > index e03cc97297aa..c03925bea655 100644
> > --- a/tools/power/cpupower/utils/helpers/helpers.h
> > +++ b/tools/power/cpupower/utils/helpers/helpers.h
> > @@ -140,6 +140,8 @@ extern int cpufreq_has_boost_support(unsigned int cpu, int *support,
> >  
> >  /* AMD P-States stuff **************************/
> >  extern bool cpupower_amd_pstate_enabled(void);
> > +extern void amd_pstate_boost_init(unsigned int cpu,
> > +				  int *support, int *active);
> >  
> >  /* AMD P-States stuff **************************/
> >  
> > @@ -177,6 +179,9 @@ static inline int cpufreq_has_boost_support(unsigned int cpu, int *support,
> >  
> >  static inline bool cpupower_amd_pstate_enabled(void)
> >  { return false; }
> > +static void amd_pstate_boost_init(unsigned int cpu,
> > +				  int *support, int *active)
> > +{ return; }
> 
> I don't believe the return statement is needed here, can just be {}
> 

Updated.

Thanks,
Ray