a05bab362f
This adds the new function pointer PCArch.clockinit(), which is a timer dependent initialization routine. It also takes over the job of guesscpuhz(). This way, the architecture ident code can switch between different timers (i8253, HPET and XEN timer).
127 lines
2.1 KiB
C
127 lines
2.1 KiB
C
#include "u.h"
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#include "../port/lib.h"
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#include "mem.h"
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#include "dat.h"
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#include "fns.h"
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#include "io.h"
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/*
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* HPET timer
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*
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* The HPET timer is memory mapped which allows
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* faster access compared to the classic i8253.
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* This timer is not used to generate interrupts
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* as we use the LAPIC timer for that.
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* Its purpose is to measure the LAPIC timer
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* and TSC frequencies.
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*/
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enum {
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Cap = 0x00/4,
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Period = 0x04/4,
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Config = 0x10/4,
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Isr = 0x20/4,
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Ctrlo = 0xF0/4,
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Ctrhi = 0xF4/4,
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};
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static struct {
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Lock;
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u32int *mmio;
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uvlong last;
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uvlong freq;
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} hpet;
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int
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hpetprobe(uvlong pa)
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{
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u32int cap, period;
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int mhz;
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if((hpet.mmio = vmap(pa, 1024)) == nil)
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return -1;
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cap = hpet.mmio[Cap];
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period = hpet.mmio[Period];
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if(period == 0 || period > 0x05F4E100)
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return -1;
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hpet.freq = 1000000000000000ULL / period;
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mhz = (hpet.freq + 500000) / 1000000;
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print("HPET: %llux %.8ux %d MHz \n", pa, cap, mhz);
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return 0;
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}
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static uvlong
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hpetcpufreq(void)
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{
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u32int x, y;
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uvlong a, b;
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int loops;
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ilock(&hpet);
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for(loops = 1000;;loops += 1000){
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cycles(&a);
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x = hpet.mmio[Ctrlo];
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aamloop(loops);
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cycles(&b);
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y = hpet.mmio[Ctrlo] - x;
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if(y >= hpet.freq/HZ || loops >= 1000000)
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break;
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}
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iunlock(&hpet);
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if(m->havetsc && b > a){
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b -= a;
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m->cyclefreq = b * hpet.freq / y;
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m->aalcycles = (b + loops-1) / loops;
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return m->cyclefreq;
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}
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return (vlong)loops*m->aalcycles * hpet.freq / y;
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}
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void
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hpetinit(void)
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{
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uvlong cpufreq;
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if(m->machno != 0){
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m->cpuhz = MACHP(0)->cpuhz;
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m->cpumhz = MACHP(0)->cpumhz;
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m->cyclefreq = MACHP(0)->cyclefreq;
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m->loopconst = MACHP(0)->loopconst;
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return;
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}
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/* start counting */
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hpet.mmio[Config] |= 1;
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/* measure loopconst for delay() and tsc frequencies */
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cpufreq = hpetcpufreq();
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m->loopconst = (cpufreq/1000)/m->aalcycles; /* AAM+LOOP's for 1 ms */
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m->cpuhz = cpufreq;
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/* round to the nearest megahz */
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m->cpumhz = (cpufreq+500000)/1000000L;
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if(m->cpumhz == 0)
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m->cpumhz = 1;
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}
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uvlong
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hpetread(uvlong *hz)
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{
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uvlong ticks;
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if(hz != nil)
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*hz = hpet.freq;
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ilock(&hpet);
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ticks = hpet.last;
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ticks += hpet.mmio[Ctrlo] - (u32int)ticks;
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hpet.last = ticks;
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iunlock(&hpet);
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return ticks;
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}
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