linux-kernel - Re: [PATCH 1/3] arm64/cpufeature.h: Add macros for a cpu features testing

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Date:	Fri, 04 Sep 2015 13:00:10 +0100
From:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
To:	Alexander Kuleshov <kuleshovmail@...il.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>
CC:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] arm64/cpufeature.h: Add macros for a cpu features
 testing

On 03/09/15 19:11, Alexander Kuleshov wrote:
> This patch provides a couple of macros for the testing of processor
> features (crypto and FP/SIMD) like support of SHA1, AES instructions,
> support for FPU and etc. There is already a couple of places in the
> arch/arm64/kernel where these processor features are tested and these
> macros are facilitate this.
>
> Signed-off-by: Alexander Kuleshov <kuleshovmail@...il.com>
> ---
>   arch/arm64/include/asm/cpufeature.h | 44 +++++++++++++++++++++++++++++++++++++
>   1 file changed, 44 insertions(+)
>
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index c104421..2919455 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -28,7 +28,50 @@
>
>   #define ARM64_NCAPS				4
>
> +/*
> + * ID_AA64ISAR0_EL1 AES, bits [7:4]
> + */
> +#define ID_AA64ISAR0_EL1_AES_MASK	4
> +#define ID_AA64ISAR0_EL1_AES(feature)	\
> +	(((feature >> ID_AA64ISAR0_EL1_AES_MASK) & 0xf) & 1UL)
> +#define ID_AA64ISAR0_EL1_PMULL(feature)	\
> +	(((feature >> ID_AA64ISAR0_EL1_AES_MASK) & 0xf) & 2UL)
> +


There is generic CPUID feature helper queued for 4.3, which can extract
the feature bits

  cpuid_feature_extract_field(feature, shift)

You might want to use it instead. Btw, I have a patch series(waiting for
the merge window, before I post), which changes the way we initialise the
HWCAP bits.

Thanks
Suzuki

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