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apic: fix lapic timer divider (fixes wrong lapic frequency on boot)

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loading the divider before programming one shot mode *sometimes*
gives the wrong frequency. (X200s got 192Mhz vs. 266Mhz, after
5 boot attempts)

also reload the divider after programming periodic mode. (from
http://wiki.osdev.org/APIC_timer)
This commit is contained in:
cinap_lenrek 2013-06-22 00:47:24 +02:00
parent a59b0bd6a8
commit 3487653524
1 changed files with 7 additions and 1 deletions
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8
sys/src/9/pc/apic.c
View file

@ -124,6 +124,12 @@ lapiconline(void)
lapicw(LapicTICR, lapictimer.max);
lapicw(LapicTIMER, LapicCLKIN|LapicPERIODIC|(VectorPIC+IrqTIMER));
/*
* not strickly neccesary, but reported (osdev.org) to be
* required for some machines.
*/
lapicw(LapicTDCR, lapictdxtab[lapictimer.tdx]);
lapicw(LapicTPR, 0);
}
@ -134,8 +140,8 @@ static void
lapictimerinit(void)
{
Retry:
lapicw(LapicTDCR, lapictdxtab[lapictimer.tdx]);
lapicw(LapicTIMER, ApicIMASK|LapicCLKIN|LapicONESHOT|(VectorPIC+IrqTIMER));
lapicw(LapicTDCR, lapictdxtab[lapictimer.tdx]);
if(lapictimer.hz == 0ULL){
uvlong x, v, hz;