Hi Catalin
> -----Original Message-----
> From: Catalin Marinas <catalin.mari...@arm.com>
> Sent: 2019年9月24日 0:07
> To: Justin He (Arm Technology China) <justin...@arm.com>
> Cc: Will Deacon <w...@kernel.org>; Mark Rutland
> <mark.rutl...@arm.com>; James Morse <james.mo...@arm.com>; Marc
> Zyngier <m...@kernel.org>; Matthew Wilcox <wi...@infradead.org>; Kirill A.
> Shutemov <kirill.shute...@linux.intel.com>; linux-arm-
> ker...@lists.infradead.org; linux-kernel@vger.kernel.org; linux-
> m...@kvack.org; Suzuki Poulose <suzuki.poul...@arm.com>; Punit
> Agrawal <punitagra...@gmail.com>; Anshuman Khandual
> <anshuman.khand...@arm.com>; Alex Van Brunt
> <avanbr...@nvidia.com>; Robin Murphy <robin.mur...@arm.com>;
> Thomas Gleixner <t...@linutronix.de>; Andrew Morton <akpm@linux-
> foundation.org>; Jérôme Glisse <jgli...@redhat.com>; Ralph Campbell
> <rcampb...@nvidia.com>; hejia...@gmail.com; Kaly Xin (Arm Technology
> China) <kaly....@arm.com>; nd <n...@arm.com>
> Subject: Re: [PATCH v8 1/3] arm64: cpufeature: introduce helper
> cpu_has_hw_af()
>
> On Sat, Sep 21, 2019 at 09:50:52PM +0800, Jia He wrote:
> > We unconditionally set the HW_AFDBM capability and only enable it on
> > CPUs which really have the feature. But sometimes we need to know
> > whether this cpu has the capability of HW AF. So decouple AF from
> > DBM by new helper cpu_has_hw_af().
> >
> > Reported-by: kbuild test robot <l...@intel.com>
> > Suggested-by: Suzuki Poulose <suzuki.poul...@arm.com>
> > Signed-off-by: Jia He <justin...@arm.com>
> > ---
> > arch/arm64/include/asm/cpufeature.h | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/arch/arm64/include/asm/cpufeature.h
> b/arch/arm64/include/asm/cpufeature.h
> > index c96ffa4722d3..46caf934ba4e 100644
> > --- a/arch/arm64/include/asm/cpufeature.h
> > +++ b/arch/arm64/include/asm/cpufeature.h
> > @@ -667,6 +667,16 @@ static inline u32
> id_aa64mmfr0_parange_to_phys_shift(int parange)
> > default: return CONFIG_ARM64_PA_BITS;
> > }
> > }
> > +
> > +/* Decouple AF from AFDBM. */
>
> We could do with a better comment here or just remove it altogether. The
> aim of the patch was to decouple AF check from the AF+DBM but the
> comment here should describe what the function does. Maybe something
> like: "Check whether hardware update of the Access flag is supported".
>
Okay, I will update it
--
Cheers,
Justin (Jia He)
> > +static inline bool cpu_has_hw_af(void)
> > +{
> > + if (IS_ENABLED(CONFIG_ARM64_HW_AFDBM))
> > + return read_cpuid(ID_AA64MMFR1_EL1) & 0xf;
> > +
> > + return false;
> > +}
>
> Other than the comment above,
>
> Reviewed-by: Catalin Marinas <catalin.mari...@arm.com>
