205 lines
3.2 KiB
C
205 lines
3.2 KiB
C
/*
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* bcm2835 timers
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* System timers run at 1MHz (timers 1 and 2 are used by GPU)
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* ARM timer usually runs at 250MHz (may be slower in low power modes)
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* Cycle counter runs at 700MHz (unless overclocked)
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* All are free-running up-counters
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*
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* Use system timer 3 (64 bits) for hzclock interrupts and fastticks
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* Use ARM timer (32 bits) for perfticks
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* Use ARM timer to force immediate interrupt
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* Use cycle counter for cycles()
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*/
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#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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enum {
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SYSTIMERS = VIRTIO+0x3000,
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ARMTIMER = VIRTIO+0xB400,
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SystimerFreq = 1*Mhz,
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MaxPeriod = SystimerFreq / HZ,
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MinPeriod = SystimerFreq / (100*HZ),
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};
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typedef struct Systimers Systimers;
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typedef struct Armtimer Armtimer;
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struct Systimers {
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u32int cs;
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u32int clo;
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u32int chi;
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u32int c0;
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u32int c1;
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u32int c2;
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u32int c3;
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};
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struct Armtimer {
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u32int load;
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u32int val;
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u32int ctl;
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u32int irqack;
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u32int irq;
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u32int maskedirq;
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u32int reload;
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u32int predivider;
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u32int count;
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};
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enum {
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CntPrescaleShift= 16, /* freq is sys_clk/(prescale+1) */
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CntPrescaleMask = 0xFF,
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CntEnable = 1<<9,
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TmrDbgHalt = 1<<8,
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TmrEnable = 1<<7,
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TmrIntEnable = 1<<5,
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TmrPrescale1 = 0x00<<2,
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TmrPrescale16 = 0x01<<2,
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TmrPrescale256 = 0x02<<2,
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CntWidth16 = 0<<1,
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CntWidth32 = 1<<1,
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};
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static void
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clockintr(Ureg *ureg, void *)
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{
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Systimers *tn;
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tn = (Systimers*)SYSTIMERS;
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/* dismiss interrupt */
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tn->cs = 1<<3;
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timerintr(ureg, 0);
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}
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void
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clockshutdown(void)
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{
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Armtimer *tm;
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tm = (Armtimer*)ARMTIMER;
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tm->ctl = 0;
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}
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void
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clockinit(void)
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{
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Systimers *tn;
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Armtimer *tm;
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u32int t0, t1, tstart, tend;
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tn = (Systimers*)SYSTIMERS;
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tm = (Armtimer*)ARMTIMER;
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tm->load = 0;
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tm->ctl = TmrPrescale1|CntEnable|CntWidth32;
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coherence();
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tstart = tn->clo;
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do{
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t0 = lcycles();
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}while(tn->clo == tstart);
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tend = tstart + 10000;
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do{
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t1 = lcycles();
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}while(tn->clo != tend);
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t1 -= t0;
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m->cpuhz = 100 * t1;
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m->cpumhz = (m->cpuhz + Mhz/2 - 1) / Mhz;
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m->cyclefreq = m->cpuhz;
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tn->c3 = tn->clo - 1;
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intrenable(IRQtimer3, clockintr, nil, 0, "clock");
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}
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void
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timerset(uvlong next)
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{
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Systimers *tn;
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vlong now, period;
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tn = (Systimers*)SYSTIMERS;
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now = fastticks(nil);
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period = next - fastticks(nil);
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if(period < MinPeriod)
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next = now + MinPeriod;
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else if(period > MaxPeriod)
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next = now + MaxPeriod;
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tn->c3 = (ulong)next;
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}
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uvlong
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fastticks(uvlong *hz)
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{
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Systimers *tn;
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ulong lo, hi;
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tn = (Systimers*)SYSTIMERS;
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if(hz)
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*hz = SystimerFreq;
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do{
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hi = tn->chi;
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lo = tn->clo;
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}while(tn->chi != hi);
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m->fastclock = (uvlong)hi<<32 | lo;
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return m->fastclock;
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}
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ulong
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perfticks(void)
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{
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Armtimer *tm;
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tm = (Armtimer*)ARMTIMER;
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return tm->count;
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}
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void
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armtimerset(int n)
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{
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Armtimer *tm;
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tm = (Armtimer*)ARMTIMER;
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if(n > 0){
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tm->ctl |= TmrEnable|TmrIntEnable;
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tm->load = n;
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}else{
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tm->load = 0;
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tm->ctl &= ~(TmrEnable|TmrIntEnable);
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tm->irq = 1;
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}
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coherence();
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}
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ulong
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µs(void)
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{
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if(SystimerFreq != 1*Mhz)
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return fastticks2us(fastticks(nil));
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return fastticks(nil);
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}
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void
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microdelay(int n)
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{
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Systimers *tn;
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u32int now, diff;
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tn = (Systimers*)SYSTIMERS;
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diff = n + 1;
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now = tn->clo;
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while(tn->clo - now < diff)
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;
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}
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void
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delay(int n)
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{
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while(--n >= 0)
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microdelay(1000);
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}
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