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Subject: Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt
From: Lee Revell <rlrevell@joe-job.com>
To: Nish Aravamudan <nish.aravamudan@gmail.com>
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Date: Sat, 16 Jul 2005 23:55:17 -0400
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On Sat, 2005-07-16 at 19:35 -0700, Nish Aravamudan wrote: 
> As you've seen, I think it depends on the timesource: for the PIT, it
> would be arch/i386/kernel/timers/timer_pit.c::setup_pit_timer().

That one looks pretty straightforward.
arch/i386/kernel/timers/timer_tsc.c really looks like fun.  So many
corner cases...

BTW shouldn't this code from mark_offset_tsc():

402         if (pit_latch_buggy) {
403                 /* get center value of last 3 time lutch */
404                 if ((count2 >= count && count >= count1)
405                     || (count1 >= count && count >= count2)) {
406                         count2 = count1; count1 = count;
407                 } else if ((count1 >= count2 && count2 >= count)
408                            || (count >= count2 && count2 >= count1)) {
409                         countmp = count;count = count2;
410                         count2 = count1;count1 = countmp;
411                 } else {
412                         count2 = count1; count1 = count; count = count1;
413                 }
414         }

use an ifdef?  It only applies to cyrix_55x0, and mark_offset_tsc is a
pretty hot path.

Lee