linux-kernel - Re: [PATCH 3/8] cpupower: Add CPUPOWER_CAP_AMD_HW

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Date:   Fri, 22 Jan 2021 13:23:08 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Nathan Fontenot <nathan.fontenot@....com>, rrichter@....com,
        shuah@...nel.org, linux-kernel@...r.kernel.org, trenn@...e.com,
        linux-pm@...r.kernel.org, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH 3/8] cpupower: Add CPUPOWER_CAP_AMD_HW_PSTATE cpuid caps
 flag

On 1/22/21 10:38 AM, Nathan Fontenot wrote:
> Add a check in get_cpu_info() for the ability to read frequencies
> from hardware and set the CPUPOWER_CAP_AMD_HW_PSTATE cpuid flag.
> The cpuid flag is set when CPUID_80000007_EDX[7] is set,
> which is all families >= 10h. The check excludes family 14h
> because HW pstate reporting was not implemented on family 14h.
> 
> This is intended to reduce family checks in the main code paths.
> 
> Signed-off-by: Nathan Fontenot <nathan.fontenot@....com>
> ---
>   tools/power/cpupower/utils/helpers/amd.c     |    6 +-----
>   tools/power/cpupower/utils/helpers/cpuid.c   |   12 +++++++++---
>   tools/power/cpupower/utils/helpers/helpers.h |    1 +
>   3 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/power/cpupower/utils/helpers/amd.c b/tools/power/cpupower/utils/helpers/amd.c
> index 34368436bbd6..496844a20fe2 100644
> --- a/tools/power/cpupower/utils/helpers/amd.c
> +++ b/tools/power/cpupower/utils/helpers/amd.c
> @@ -94,11 +94,7 @@ int decode_pstates(unsigned int cpu, unsigned int cpu_family,
>   	union core_pstate pstate;
>   	unsigned long long val;
>   
> -	/* Only read out frequencies from HW when CPU might be boostable
> -	   to keep the code as short and clean as possible.
> -	   Otherwise frequencies are exported via ACPI tables.
> -	*/

Please update comment instead of deleting it.

> -	if (cpu_family < 0x10 || cpu_family == 0x14)
> +	if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_AMD_HW_PSTATE))
>   		return -1;
>   
>   	if (read_msr(cpu, MSR_AMD_PSTATE_LIMIT, &val))
> diff --git a/tools/power/cpupower/utils/helpers/cpuid.c b/tools/power/cpupower/utils/helpers/cpuid.c
> index f9a66a430b72..d577220a193b 100644
> --- a/tools/power/cpupower/utils/helpers/cpuid.c
> +++ b/tools/power/cpupower/utils/helpers/cpuid.c
> @@ -128,9 +128,15 @@ int get_cpu_info(struct cpupower_cpu_info *cpu_info)
>   	/* AMD or Hygon Boost state enable/disable register */
>   	if (cpu_info->vendor == X86_VENDOR_AMD ||
>   	    cpu_info->vendor == X86_VENDOR_HYGON) {
> -		if (ext_cpuid_level >= 0x80000007 &&
> -		    (cpuid_edx(0x80000007) & (1 << 9)))
> -			cpu_info->caps |= CPUPOWER_CAP_AMD_CPB;
> +		if (ext_cpuid_level >= 0x80000007) {
> +			if (cpuid_edx(0x80000007) & (1 << 9))
> +				cpu_info->caps |= CPUPOWER_CAP_AMD_CPB;
> +
> +			if ((cpuid_edx(0x80000007) & (1 << 7)) &&
> +			    cpu_info->family != 0x14)
> +				/* HW pstate was not implemented in family 0x14 */
> +				cpu_info->caps |= CPUPOWER_CAP_AMD_HW_PSTATE;
> +		}
>   
>   		if (ext_cpuid_level >= 0x80000008 &&
>   		    cpuid_ebx(0x80000008) & (1 << 4))
> diff --git a/tools/power/cpupower/utils/helpers/helpers.h b/tools/power/cpupower/utils/helpers/helpers.h
> index a84f85a9dbd2..5f61eefff5b2 100644
> --- a/tools/power/cpupower/utils/helpers/helpers.h
> +++ b/tools/power/cpupower/utils/helpers/helpers.h
> @@ -70,6 +70,7 @@ enum cpupower_cpu_vendor {X86_VENDOR_UNKNOWN = 0, X86_VENDOR_INTEL,
>   #define CPUPOWER_CAP_IS_SNB		0x00000020
>   #define CPUPOWER_CAP_INTEL_IDA		0x00000040
>   #define CPUPOWER_CAP_AMD_RDPRU		0x00000080
> +#define CPUPOWER_CAP_AMD_HW_PSTATE	0x00000100
>   
>   #define CPUPOWER_AMD_CPBDIS		0x02000000
>   
> 
> 

thanks,
-- Shuah