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

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Date:   Tue, 2 Nov 2021 15:11:09 -0500
From:   Nathan Fontenot <nafonten@....com>
To:     Huang Rui <ray.huang@....com>,
        "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
Cc:     Deepak Sharma <deepak.sharma@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Mario Limonciello <mario.limonciello@....com>,
        Steven Noonan <steven@...vesoftware.com>,
        Nathan Fontenot <nathan.fontenot@....com>,
        Jinzhou Su <Jinzhou.Su@....com>,
        Xiaojian Du <Xiaojian.Du@....com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v3 18/21] cpupower: enable boost state support for
 amd-pstate module



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 {}

-Nathan

>  
>  /* cpuid and cpuinfo helpers  **************************/
>  
> diff --git a/tools/power/cpupower/utils/helpers/misc.c b/tools/power/cpupower/utils/helpers/misc.c
> index 0c483cdefcc2..e0d3145434d3 100644
> --- a/tools/power/cpupower/utils/helpers/misc.c
> +++ b/tools/power/cpupower/utils/helpers/misc.c
> @@ -41,6 +41,8 @@ int cpufreq_has_boost_support(unsigned int cpu, int *support, int *active,
>  			if (ret)
>  				return ret;
>  		}
> +	} else if (cpupower_cpu_info.caps & CPUPOWER_CAP_AMD_PSTATE) {
> +		amd_pstate_boost_init(cpu, support, active);
>  	} else if (cpupower_cpu_info.caps & CPUPOWER_CAP_INTEL_IDA)
>  		*support = *active = 1;
>  	return 0;
>