Messages in this thread | | | Subject | Re: [PATCH v4 1/3] arm64: cpufeature: introduce helper cpu_has_hw_af() | From | Suzuki K Poulose <> | Date | Wed, 18 Sep 2019 15:20:41 +0100 |
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Hi Jia,
On 18/09/2019 14:19, 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(). > > Signed-off-by: Jia He <justin.he@arm.com> > Suggested-by: Suzuki Poulose <Suzuki.Poulose@arm.com> > --- > arch/arm64/include/asm/cpufeature.h | 1 + > arch/arm64/kernel/cpufeature.c | 6 ++++++ > 2 files changed, 7 insertions(+) > > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h > index c96ffa4722d3..206b6e3954cf 100644 > --- a/arch/arm64/include/asm/cpufeature.h > +++ b/arch/arm64/include/asm/cpufeature.h > @@ -390,6 +390,7 @@ extern DECLARE_BITMAP(boot_capabilities, ARM64_NPATCHABLE); > for_each_set_bit(cap, cpu_hwcaps, ARM64_NCAPS) > > bool this_cpu_has_cap(unsigned int cap); > +bool cpu_has_hw_af(void); > void cpu_set_feature(unsigned int num); > bool cpu_have_feature(unsigned int num); > unsigned long cpu_get_elf_hwcap(void); > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index b1fdc486aed8..c5097f58649d 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -1141,6 +1141,12 @@ static bool has_hw_dbm(const struct arm64_cpu_capabilities *cap, > return true; > } > > +/* Decouple AF from AFDBM. */ > +bool cpu_has_hw_af(void) > +{ Sorry for not having asked this earlier. Are we interested in,
"whether *this* CPU has AF support ?" or "whether *at least one* CPU has the AF support" ? The following code does the former.
> + return (read_cpuid(ID_AA64MMFR1_EL1) & 0xf);
Getting the latter is tricky, and I think it is what we are looking for here. In which case we may need something more to report this.
Kind regards Suzuki
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