2002/0410/pc/i8253.c (diff list | history)

pc/i8253.c on 1997/0327
1997/0327		#include "u.h" #include "../port/lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "io.h" /* * 8253 timer */ enum { T0cntr= 0x40, /* counter ports */ T1cntr= 0x41, /* ... */ T2cntr= 0x42, /* ... */
2000/0622		Tmode= 0x43, /* mode port (control word register) */
2000/0623		T2ctl= 0x61, /* counter 2 control port */
1997/0327		/* commands */ Latch0= 0x00, /* latch counter 0's value */
2000/0622		Load0l= 0x10, /* load counter 0's lsb */ Load0m= 0x20, /* load counter 0's msb */
1997/0327		Load0= 0x30, /* load counter 0 with 2 bytes */
2002/0405		Latch1= 0x40, /* latch counter 1's value */ Load1l= 0x50, /* load counter 1's lsb */ Load1m= 0x60, /* load counter 1's msb */ Load1= 0x70, /* load counter 1 with 2 bytes */
2000/0623		Latch2= 0x80, /* latch counter 2's value */ Load2l= 0x90, /* load counter 2's lsb */ Load2m= 0xa0, /* load counter 2's msb */ Load2= 0xb0, /* load counter 2 with 2 bytes */
1997/0327
2000/0623		/* 8254 read-back command: everything > pc-at has an 8254 */ Rdback= 0xc0, /* readback counters & status */ Rdnstat=0x10, /* don't read status */ Rdncnt= 0x20, /* don't read counter value */ Rd0cntr=0x02, /* read back for which counter */ Rd1cntr=0x04, Rd2cntr=0x08,
1997/0327		/* modes */
2000/0623		ModeMsk=0xe,
2000/0622		Square= 0x6, /* periodic square wave */
2000/0623		Trigger=0x0, /* interrupt on terminal count */ Sstrobe=0x8, /* software triggered strobe */
1997/0327
2002/0409		/* T2ctl bits */ T2gate= (1<<0), /* enable T2 counting */ T2spkr= (1<<1), /* connect T2 out to speaker */ T2out= (1<<5), /* output of T2 */
1997/0327		Freq= 1193182, /* Real clock frequency */
2002/0410		Tickshift=8, /* extra accuracy */ MaxPeriod=Freq/HZ, MinPeriod=Freq/(100*HZ),
1997/0327		};
2000/0623		static struct {
2000/0627		Lock;
2002/0410		ulong period; /* current clock period */
2000/0701		int enabled;
2002/0410		uvlong hz;
2002/0405
2002/0409		ushort last; /* last value of clock 1 */ uvlong ticks; /* cumulative ticks of counter 1 */
2000/0623		}i8253;
2000/0622
2002/0410
1997/0327		void
2002/0405		i8253init(void)
1997/0327		{
2002/0405		int loops, x;
1997/0327
2002/0405		ioalloc(T0cntr, 4, 0, "i8253"); ioalloc(T2ctl, 1, 0, "i8253.cntr2ctl");
2000/0623
2002/0405		/*
2002/0410		* enable a 1/HZ interrupt for providing scheduling interrupts
2002/0405		*/ outb(Tmode, Load0|Square); outb(T0cntr, (Freq/HZ)); /* low byte */ outb(T0cntr, (Freq/HZ)>>8); /* high byte */
2002/0410		i8253.period = Freq/HZ;
1998/0903
2002/0405		/*
2002/0409		* enable a longer period counter to use as a clock
2002/0405		*/
2002/0409		outb(Tmode, Load2|Square); outb(T2cntr, 0); /* low byte */ outb(T2cntr, 0); /* high byte */
2002/0410		i8253.period = Freq/HZ;
2002/0409		x = inb(T2ctl); x |= T2gate; outb(T2ctl, x);
2002/0410
2002/0405		/* * Introduce a little delay to make sure the count is * latched and the timer is counting down; with a fast * enough processor this may not be the case. * The i8254 (which this probably is) has a read-back * command which can be used to make sure the counting * register has been written into the counting element. */ x = (Freq/HZ); for(loops = 0; loops < 100000 && x >= (Freq/HZ); loops++){ outb(Tmode, Latch0); x = inb(T0cntr); x |= inb(T0cntr)<<8;
1997/0327		}
2002/0405		}
1997/0327
2002/0405		void guesscpuhz(int aalcycles) { int cpufreq, loops, incr, x, y; vlong a, b;
1997/0327		/* find biggest loop that doesn't wrap */ incr = 16000000/(aalcycles*HZ*2); x = 2000; for(loops = incr; loops < 64*1024; loops += incr) { /* * measure time for the loop * * MOVL loops,CX * aaml1: AAM * LOOP aaml1 * * the time for the loop should be independent of external * cache and memory system since it fits in the execution * prefetch buffer. * */
2002/0404		outb(Tmode, Latch0);
2002/0405		if(m->havetsc) rdtsc(&a);
1997/0327		x = inb(T0cntr); x |= inb(T0cntr)<<8; aamloop(loops);
2002/0405		outb(Tmode, Latch0); if(m->havetsc)
2001/1130		rdtsc(&b);
1997/0327		y = inb(T0cntr); y |= inb(T0cntr)<<8; x -= y;
2002/0405
1997/0327		if(x < 0) x += Freq/HZ; if(x > Freq/(3*HZ)) break; }
2002/0405
1997/0327		/* * figure out clock frequency and a loop multiplier for delay().
1999/0131		* n.b. counter goes up by 2*Freq
1997/0327		*/
1999/0131		cpufreq = loops*((aalcycles*2*Freq)/x);
1997/0327		m->loopconst = (cpufreq/1000)/aalcycles; /* AAM+LOOP's for 1 ms */
1999/0131
2002/0405		if(m->havetsc){
1999/0131		/* counter goes up by 2*Freq */ b = (b-a)<<1; b *= Freq; b /= x; /* * round to the nearest megahz */ m->cpumhz = (b+500000)/1000000L; m->cpuhz = b; } else { /* * add in possible 0.5% error and convert to MHz */ m->cpumhz = (cpufreq + cpufreq/200)/1000000; m->cpuhz = cpufreq; }
2002/0410		i8253.hz = Freq<<Tickshift;
1997/0327		}
2002/0410		ulong i8253periodset; void i8253timerset(uvlong next)
2000/0621		{
2002/0410		ulong period; ulong want; ulong now;
2000/0623
2002/0410		want = next>>Tickshift; now = i8253.ticks; /* assuming whomever called us just did fastticks() */
2000/0627
2002/0410		period = MaxPeriod; if(next != 0){ period = want - now; if(period < MinPeriod) period = MinPeriod; else if(period > (4*MaxPeriod)/5) /* strong attraction to MaxPeriod */ period = MaxPeriod;
2000/0627		}
2000/0623
2002/0410		/* histeresis */ if(i8253.period != period){ ilock(&i8253); /* load new value */ outb(Tmode, Load0|Square); outb(T0cntr, period); /* low byte */ outb(T0cntr, period>>8); /* high byte */
2000/0701
2002/0410		/* remember period */ i8253.period = period; i8253periodset++; iunlock(&i8253);
2000/0701		}
2000/0627		} static void
2002/0410		i8253clock(Ureg* ureg, void*)
2000/0627		{
2002/0410		timerintr(ureg, 0);
2000/0621		}
1997/0327		void i8253enable(void) {
2000/0701		i8253.enabled = 1;
2002/0410		i8253.period = Freq/HZ; intrenable(IrqCLOCK, i8253clock, 0, BUSUNKNOWN, "clock");
1997/0327		}
1998/0710		/*
2002/0405		* return the total ticks of counter 1. We shift by * 8 to give timesync more wriggle room for interpretation * of the frequency
1998/0710		*/ uvlong i8253read(uvlong *hz) {
2002/0405		ushort y, x; uvlong ticks;
1998/0710		if(hz)
2002/0410		*hz = i8253.hz;
2002/0405
2002/0409		ilock(&i8253); outb(Tmode, Latch2); y = inb(T2cntr); y |= inb(T2cntr)<<8;
2002/0405
2002/0409		if(y < i8253.last) x = i8253.last - y;
2002/0405		else
2002/0410		x = i8253.last + (0x10000 - y);
2002/0409		i8253.last = y; i8253.ticks += x>>1; ticks = i8253.ticks; iunlock(&i8253);
2002/0405
2002/0409		return ticks<<Tickshift;
2002/0405		}
2002/0410		void delay(int millisecs)
2002/0405		{
2002/0410		millisecs *= m->loopconst; if(millisecs <= 0) millisecs = 1; aamloop(millisecs); } void microdelay(int microsecs) { microsecs *= m->loopconst; microsecs /= 1000; if(microsecs <= 0) microsecs = 1; aamloop(microsecs); } ulong TK2MS(ulong ticks) { uvlong t, hz; t = ticks; hz = HZ; t *= 1000L; t = t/hz; ticks = t; return ticks;
1998/0710		}