linux-kernel - Re: [PATCH RESEND v6 7/9] cpupower: Enable boost state support for AMD P-State module

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Date:   Fri, 18 Feb 2022 17:01:59 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Huang Rui <ray.huang@....com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        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>,
        Perry Yuan <Perry.Yuan@....com>,
        Jassmine Meng <li.meng@....com>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        linux-kernel@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH RESEND v6 7/9] cpupower: Enable boost state support for
 AMD P-State module

On 2/16/22 12:35 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-State 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.

Nit - 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-State 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 4d45d1b44164..f5ba528dc7db 100644
> --- a/tools/power/cpupower/utils/helpers/amd.c
> +++ b/tools/power/cpupower/utils/helpers/amd.c
> @@ -175,5 +175,23 @@ 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 = acpi_cppc_get_data(cpu, 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-State 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 557524078e94..f142fbfa4a77 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-State stuff **************************/
>   extern bool cpupower_amd_pstate_enabled(void);
> +extern void amd_pstate_boost_init(unsigned int cpu,
> +				  int *support, int *active);
>   
>   /* AMD P-State 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; }

No need for a return here

>   
>   /* 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;
> 

thanks,
-- Shuah