linux-kernel - Re: [PATCH v2] arm64: Refactor conditional logic

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Message-ID: <5e836e52-bc10-462b-b819-f3e4d33bf876@arm.com>
Date: Fri, 15 Nov 2024 09:55:35 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Hardevsinh Palaniya <hardevsinh.palaniya@...iconsignals.io>,
 will@...nel.org, broonie@...nel.org
Cc: Catalin Marinas <catalin.marinas@....com>,
 Oliver Upton <oliver.upton@...ux.dev>, Marc Zyngier <maz@...nel.org>,
 Ard Biesheuvel <ardb@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Joey Gouly <joey.gouly@....com>, Ryan Roberts <ryan.roberts@....com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arm64: Refactor conditional logic

A small nit.

The subject line could have been more specific to where this
change applies (example below), otherwise it is too broad in
the entire arm64 platform context.

arm64/cpufeature: Refactor conditional logic in init_cpu_ftr_reg()

On 11/14/24 19:52, Hardevsinh Palaniya wrote:
> Unnecessarily checks ftr_ovr == tmp in an extra else if, which is not
> needed because that condition would already be true by default if the
> previous conditions are not satisfied.
> 
> 		if (ftr_ovr != tmp) {
> 		} else if (ftr_new != tmp) {
> 		} else if (ftr_ovr == tmp) {
> 
> Logic: The first and last conditions are inverses of each other, so 
> the last condition must be true if the first two conditions are false.
> 
> Additionally, all branches set the variable str, making the subsequent
> "if (str)" check redundant
> 
> Reviewed-by: Mark Brown <broonie@...nel.org>
> Signed-off-by: Hardevsinh Palaniya <hardevsinh.palaniya@...iconsignals.io>
> ---
> 
> Changelog in V2:
> 
> - remove str check 
> 
> Change in V3:
> 
> - Add logic in commit msg 
> - Add review tag
> ---
>  arch/arm64/kernel/cpufeature.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 718728a85430..728709483fb7 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -989,17 +989,16 @@ static void init_cpu_ftr_reg(u32 sys_reg, u64 new)
>  				/* Override was valid */
>  				ftr_new = tmp;
>  				str = "forced";
> -			} else if (ftr_ovr == tmp) {
> +			} else {
>  				/* Override was the safe value */
>  				str = "already set";
>  			}
>  
> -			if (str)
> -				pr_warn("%s[%d:%d]: %s to %llx\n",
> -					reg->name,
> -					ftrp->shift + ftrp->width - 1,
> -					ftrp->shift, str,
> -					tmp & (BIT(ftrp->width) - 1));
> +			pr_warn("%s[%d:%d]: %s to %llx\n",
> +				reg->name,
> +				ftrp->shift + ftrp->width - 1,
> +				ftrp->shift, str,
> +				tmp & (BIT(ftrp->width) - 1));
>  		} else if ((ftr_mask & reg->override->val) == ftr_mask) {
>  			reg->override->val &= ~ftr_mask;
>  			pr_warn("%s[%d:%d]: impossible override, ignored\n",

Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>