On Mon, Aug 11, 2003 at 03:02:16PM +0200, Maciej W. Rozycki wrote:
> Hello,
>
> Here is hopefully the final part (for now) of the generic time changes.
> It addresses the following problems:
>
> - */
> - if (!jiffies) {
> - timerhi = timerlo = 0;
> - mips_hpt_init(count);
> + *
> + * The first timer interrupt comes late as interrupts are
> + * enabled long after timers are initialized. Therefore the
> + * high precision timer is fast, leading to wrong gettimeoffset()
> + * calculations. We deal with it by setting it based on the
> + * number of its ticks between the second and the third interrupt.
> + * That is still somewhat imprecise, but it's a good estimate.
> + * --macro
> + */
> + j = jiffies;
> + if (j < 4) {
> + static unsigned int prev_count;
> + static int hpt_initialized;
> +
> + switch (j) {
> + case 0:
> + timerhi = timerlo = 0;
> + mips_hpt_init(count);
> + break;
> + case 2:
> + prev_count = count;
> + break;
> + case 3:
> + if (!hpt_initialized) {
> + unsigned int c3 = 3 * (count - prev_count);
> +
> + timerhi = 0;
> + timerlo = c3;
> + mips_hpt_init(count - c3);
> + hpt_initialized = 1;
> + }
> + break;
> + default:
> + break;
> + }
> }
>
The first gettimeoffset() call is way after many jiffies (~50 normally?). Such
an estimate is not necessary.
Also note jiffies can wrap around.
Jun
