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    SubjectRe: [PATCH 3/5] cpufreq: Add APERF/MPERF support for AMD processors
    From: Thomas Renninger <trenn@suse.de>
    Date: Thu, Mar 25, 2010 at 10:43:04AM +0100

    Hi Thomas,

    > On Wednesday 24 March 2010 18:46:21 Borislav Petkov wrote:
    > > From: Mark Langsdorf <mark.langsdorf@amd.com>
    > >
    > > Starting with model 10 of Family 0x10, AMD processors may have
    > > support for APERF/MPERF. Add support for identifying it and using
    > > it within cpufreq. Move the APERF/MPERF functions out of the
    > > acpi-cpufreq code and into their own file so they can easily be
    > > shared.
    > >
    > > Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>
    > > Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
    > > ---
    > > arch/x86/kernel/cpu/amd.c | 6 +++
    > > arch/x86/kernel/cpu/cpufreq/Makefile | 4 +-
    > > arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c | 44 +-----------------------
    > > arch/x86/kernel/cpu/cpufreq/mperf.c | 50 ++++++++++++++++++++++++++++
    > > arch/x86/kernel/cpu/cpufreq/mperf.h | 9 +++++
    > > arch/x86/kernel/cpu/cpufreq/powernow-k8.c | 8 ++++
    > > 6 files changed, 77 insertions(+), 44 deletions(-)
    > > create mode 100644 arch/x86/kernel/cpu/cpufreq/mperf.c
    > > create mode 100644 arch/x86/kernel/cpu/cpufreq/mperf.h
    > >
    > > diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
    > > index e485825..796f662 100644
    > > --- a/arch/x86/kernel/cpu/amd.c
    > > +++ b/arch/x86/kernel/cpu/amd.c
    > > @@ -537,6 +537,12 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
    > > set_cpu_cap(c, X86_FEATURE_MFENCE_RDTSC);
    > > }
    > >
    > > + if (c->cpuid_level >= 6) {
    > > + unsigned ecx = cpuid_ecx(6);
    > > + if (ecx & 0x01)
    > > + set_cpu_cap(c, X86_FEATURE_APERFMPERF);
    > > + }
    > > +
    > Can you put this into:
    > arch/x86/kernel/cpu/common.c (or wherever it fits in general x86 cpu init code)
    > and remove this (arch/x86/kernel/cpu/intel.c):
    > if (c->cpuid_level > 6) {
    > unsigned ecx = cpuid_ecx(6);
    > if (ecx & 0x01)
    > set_cpu_cap(c, X86_FEATURE_APERFMPERF);
    > }
    >
    > an x86 maintainer might want to double check, but I expect this should work
    > for all x86 machines?

    Yes, it should. However, there's the remote, far-fetched possibility
    that other x86 vendors besides AMD and Intel, might have/plan to have
    CPUID, base function 6, ECX[1] defined as a completely different feature
    flag. And then it becomes ugly.

    Besides, this is, strictly speaking, not x86 generic code but AMD- and
    Intel-generic (huh, is there something like that? :)) code.

    So, IMO, this is a judgement call based on the current settings of the
    duplication and bloating levels of the x86 maintainers' filters :)

    Let's have some more opinions, please...

    Thanks.

    --
    Regards/Gruss,
    Boris.

    --
    Advanced Micro Devices, Inc.
    Operating Systems Research Center


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