linux-kernel - Re: [PATCH v2 04/11] ACPI: CPPC: Drop check for non zero perf ratio

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Message-ID: <ZtnHhkyPmIC6WyfQ@BLRRASHENOY1.amd.com>
Date: Thu, 5 Sep 2024 20:30:22 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: Mario Limonciello <superm1@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>, Perry Yuan <perry.yuan@....com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <linux-kernel@...r.kernel.org>,
	"open list:ACPI" <linux-acpi@...r.kernel.org>,
	"open list:CPU FREQUENCY SCALING FRAMEWORK" <linux-pm@...r.kernel.org>,
	Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH v2 04/11] ACPI: CPPC: Drop check for non zero perf ratio

On Tue, Sep 03, 2024 at 03:36:54PM -0500, Mario Limonciello wrote:
> From: Mario Limonciello <mario.limonciello@....com>
> 
> perf_ratio is a u64 and SCHED_CAPACITY_SCALE is a larg number.

s/larg/large

> Shifting by one will never have a zero value.
> 
> Drop the check.
> 
> Suggested-by: Gautham R. Shenoy <gautham.shenoy@....com>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>

Other than that, LGTM

Reviewed-by: Gautham R. Shenoy <gautham.sheoy@....com>

--
Thanks and Regards
gautham

> ---
>  arch/x86/kernel/acpi/cppc.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kernel/acpi/cppc.c b/arch/x86/kernel/acpi/cppc.c
> index 660cfeb6384ba..e65c77afab318 100644
> --- a/arch/x86/kernel/acpi/cppc.c
> +++ b/arch/x86/kernel/acpi/cppc.c
> @@ -91,13 +91,8 @@ static void amd_set_max_freq_ratio(void)
>  		return;
>  	}
>  
> -	perf_ratio = div_u64(numerator * SCHED_CAPACITY_SCALE, nominal_perf);
>  	/* midpoint between max_boost and max_P */
> -	perf_ratio = (perf_ratio + SCHED_CAPACITY_SCALE) >> 1;
> -	if (!perf_ratio) {
> -		pr_debug("Non-zero highest/nominal perf values led to a 0 ratio\n");
> -		return;
> -	}
> +	perf_ratio = (div_u64(numerator * SCHED_CAPACITY_SCALE, nominal_perf) + SCHED_CAPACITY_SCALE) >> 1;
>  
>  	freq_invariance_set_perf_ratio(perf_ratio, false);
>  }
> -- 
> 2.43.0
>