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    SubjectRe: Question: monolitic_clock, timer_{tsc,hpet} and CPUFREQ
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    On Thu, 2003-09-04 at 20:14, Dmitry Torokhov wrote:
    > I noticed that although timer_tsc registers cpufreq notifier to detect
    > frequency changes and adjust cpu_khz it does not set cyc2ns_scale. Is
    > monotonic clocks supposed to be also accurate?

    You are correct, without adjusting the cyc2ns_scale value
    monotonic_clock() will not be accurate on freq changing hardware.


    > Will something like this suffice for timer_tsc (compiled, not yet booted):
    >
    > --- 2.6.0-test4/arch/i386/kernel/timers/timer_tsc.c 2003-08-26 21:56:19.000000000 -0500
    > +++ linux-2.6.0-test4/arch/i386/kernel/timers/timer_tsc.c 2003-09-04 22:08:27.000000000 -0500
    > @@ -315,6 +315,7 @@
    > if (use_tsc) {
    > fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_ref, freq->new, ref_freq);
    > cpu_khz = cpufreq_scale(cpu_khz_ref, ref_freq, freq->new);
    > + set_cyc2ns_scale(cpu_khz/1000);
    > }
    > #endif
    > }

    Looks fine to me. Although I don't have any cpufreq enabled hardware, so
    I'm unable to test this (main cause I never added it myself).

    thanks
    -john


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