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

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Message-ID: <DB7PR08MB3082C2800CC612FCF57242A4F7880@DB7PR08MB3082.eurprd08.prod.outlook.com>
Date:   Fri, 20 Sep 2019 01:14:15 +0000
From:   "Justin He (Arm Technology China)" <Justin.He@....com>
To:     Catalin Marinas <Catalin.Marinas@....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-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.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" <hejianet@...il.com>,
        "Kaly Xin (Arm Technology China)" <Kaly.Xin@....com>
Subject: RE: [PATCH v5 1/3] arm64: cpufeature: introduce helper
 cpu_has_hw_af()


Hi Catalin
> -----Original Message-----
> From: Catalin Marinas <catalin.marinas@....com>
> Sent: 2019年9月20日 0:37
> To: Justin He (Arm Technology China) <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 (Arm Technology
> China) <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;
> }
>
Ok, thanks

--
Cheers,
Justin (Jia He)


> --
> Catalin
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