linux-kernel - Re: [PATCH v5 1/3] arm64: cpufeature: introduce helper cpu_has_hw

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Message-ID: <20190919163644.GD6472@arrakis.emea.arm.com>
Date:   Thu, 19 Sep 2019 17:36:44 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Jia He <justin.he@....com>
Cc:     Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Marc Zyngier <maz@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Suzuki Poulose <Suzuki.Poulose@....com>,
        Punit Agrawal <punitagrawal@...il.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Alex Van Brunt <avanbrunt@...dia.com>,
        Robin Murphy <robin.murphy@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        Ralph Campbell <rcampbell@...dia.com>, hejianet@...il.com,
        Kaly Xin <Kaly.Xin@....com>
Subject: Re: [PATCH v5 1/3] arm64: cpufeature: introduce helper
 cpu_has_hw_af()

On Fri, Sep 20, 2019 at 12:12:02AM +0800, Jia He wrote:
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index b1fdc486aed8..fb0e9425d286 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1141,6 +1141,16 @@ static bool has_hw_dbm(const struct arm64_cpu_capabilities *cap,
>  	return true;
>  }
>  
> +/* Decouple AF from AFDBM. */
> +bool cpu_has_hw_af(void)
> +{
> +	return (read_cpuid(ID_AA64MMFR1_EL1) & 0xf);
> +}
> +#else /* CONFIG_ARM64_HW_AFDBM */
> +bool cpu_has_hw_af(void)
> +{
> +	return false;
> +}
>  #endif

Please place this function in cpufeature.h directly, no need for an
additional function call. Something like:

static inline bool cpu_has_hw_af(void)
{
	if (IS_ENABLED(CONFIG_ARM64_HW_AFDBM))
		return read_cpuid(ID_AA64MMFR1_EL1) & 0xf;
	return false;
}

-- 
Catalin