ref: b502a62da2ec6058923db94f87ecc2d29db2fa77
dir: /os/pc/hpet.c/
#include "u.h" #include "../port/lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "io.h" /* * HPET timer * * The HPET timer is memory mapped which allows * faster access compared to the classic i8253. * This timer is not used to generate interrupts * as we use the LAPIC timer for that. * Its purpose is to measure the LAPIC timer * and TSC frequencies. */ enum { Cap = 0x00/4, Period = 0x04/4, Config = 0x10/4, Isr = 0x20/4, Ctrlo = 0xF0/4, Ctrhi = 0xF4/4, }; static struct { Lock; u32 *mmio; uvlong last; uvlong freq; } hpet; int hpetprobe(uvlong pa) { u32 cap, period; int mhz; if((hpet.mmio = vmap(pa, 1024)) == nil) return -1; cap = hpet.mmio[Cap]; period = hpet.mmio[Period]; if(period == 0 || period > 0x05F4E100) return -1; hpet.freq = 1000000000000000ULL / period; mhz = (hpet.freq + 500000) / 1000000; print("HPET: %llux %.8ux %d MHz \n", pa, cap, mhz); return 0; } static uvlong hpetcpufreq(void) { u32 x, y; uvlong a, b; int loops; ilock(&hpet); for(loops = 1000;;loops += 1000){ cycles(&a); x = hpet.mmio[Ctrlo]; aamloop(loops); cycles(&b); y = hpet.mmio[Ctrlo] - x; if(y >= hpet.freq/HZ || loops >= 1000000) break; } iunlock(&hpet); if(m->havetsc && b > a){ b -= a; m->cyclefreq = b * hpet.freq / y; m->aalcycles = (b + loops-1) / loops; return m->cyclefreq; } return (vlong)loops*m->aalcycles * hpet.freq / y; } void hpetinit(void) { uvlong cpufreq; if(m->machno != 0){ m->cpuhz = MACHP(0)->cpuhz; m->cpumhz = MACHP(0)->cpumhz; m->cyclefreq = MACHP(0)->cyclefreq; m->loopconst = MACHP(0)->loopconst; return; } /* start counting */ hpet.mmio[Config] |= 1; /* measure loopconst for delay() and tsc frequencies */ cpufreq = hpetcpufreq(); m->loopconst = (cpufreq/1000)/m->aalcycles; /* AAM+LOOP's for 1 ms */ m->cpuhz = cpufreq; /* round to the nearest megahz */ m->cpumhz = (cpufreq+500000)/1000000L; if(m->cpumhz == 0) m->cpumhz = 1; } uvlong hpetread(uvlong *hz) { uvlong ticks; if(hz != nil) *hz = hpet.freq; ilock(&hpet); ticks = hpet.last; ticks += hpet.mmio[Ctrlo] - (u32)ticks; hpet.last = ticks; iunlock(&hpet); return ticks; }