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    SubjectRe: [RFC] New Time of day proposal (updated 9/2/04)
    On Fri, Sep 03, 2004 at 12:41:22PM -0700, john stultz wrote:
    > > - cpufreq hooks to tsc.c and i386_tsc.c[*] can easily be added. For them to
    > > work _better_ than current code: can timeofday_hook() be called (with IRQs
    > > disabled) _anywhen_ from kernel context?
    > > [*] actually, only one of them needs the notifier, AFAICS...
    > Yep, that's on my list. I'm trying to keep to just cleaning up one thing
    > at a time, but since I've got to re-work the timer_tsc.c code anyway, I
    > figured I'd try to organize all the TSC related functions
    > (synchronization, cpufreq, get_cycles(), tsc_delay maybe?) into tsc.c.
    > This will simplify things if we ever get around to correctly fixing the
    > SMP systems w/ different speed cpus issue.

    What about removing cpu_freq_khz you have in your patch, adding a per-CPU
    value, and just use the value of the boot CPU for the other CPUs if
    !CONFIG_DIFFERENT_CPU_SPEEDS or something like that?

    > > - what about keeping lower-priority timesources still "active" in some sort to
    > > a) enable loading _and_ unloading timsources (even modularizing them
    > > becoms possible which should make testing easier...),
    > > b) call them every couple of seconds to verify the currently used
    > > timesource is still sane (and if not, call cpufreq_delayed_get() for
    > > example or disable the timesource). This would mean that e.g. pmtmr
    > > and pit can be used to "verify" and "backup" tsc, or otherwise...
    > > The "clock=tsc" override would only affect the priority of the
    > > timesource then, making it so large that no other timesource can
    > > "preempt" it, but doesn't avoid making other timesources available
    > > for backup and verification purposes.
    > That's totally the plan, although I want to put the control into sysfs.

    Even better. Thought about that too, but was worried you'd dislike the sysfs

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