ref: a8083462e62459b2ae8a243dc4ba88416eba03b1
dir: /os/boot/pc/clock.c/
#include "u.h"
#include "lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "io.h"
#include "ureg.h"
/*
* 8253 timer
*/
enum
{
T0cntr= 0x40, /* counter ports */
T1cntr= 0x41, /* ... */
T2cntr= 0x42, /* ... */
Tmode= 0x43, /* mode port */
/* commands */
Latch0= 0x00, /* latch counter 0's value */
Load0= 0x30, /* load counter 0 with 2 bytes */
/* modes */
Square= 0x36, /* perioic square wave */
Freq= 1193182, /* Real clock frequency */
};
static uvlong cpuhz = 66000000;
static int cpumhz = 66;
static int loopconst = 100;
int cpuidax, cpuiddx;
int havetsc;
extern void _cycles(uvlong*); /* in l.s */
extern void wrmsr(int, vlong);
static void
clockintr(Ureg*, void*)
{
m->ticks++;
checkalarms();
}
#define STEPPING(x) ((x)&0xf)
#define X86MODEL(x) (((x)>>4)&0xf)
#define X86FAMILY(x) (((x)>>8)&0xf)
enum
{
/* flags */
CpuidFPU = 0x001, /* on-chip floating point unit */
CpuidMCE = 0x080, /* machine check exception */
CpuidCX8 = 0x100, /* CMPXCHG8B instruction */
};
typedef struct
{
int family;
int model;
int aalcycles;
char *name;
} X86type;
X86type x86intel[] =
{
{ 4, 0, 22, "486DX", }, /* known chips */
{ 4, 1, 22, "486DX50", },
{ 4, 2, 22, "486SX", },
{ 4, 3, 22, "486DX2", },
{ 4, 4, 22, "486SL", },
{ 4, 5, 22, "486SX2", },
{ 4, 7, 22, "DX2WB", }, /* P24D */
{ 4, 8, 22, "DX4", }, /* P24C */
{ 4, 9, 22, "DX4WB", }, /* P24CT */
{ 5, 0, 23, "P5", },
{ 5, 1, 23, "P5", },
{ 5, 2, 23, "P54C", },
{ 5, 3, 23, "P24T", },
{ 5, 4, 23, "P55C MMX", },
{ 5, 7, 23, "P54C VRT", },
{ 6, 1, 16, "PentiumPro", },/* trial and error */
{ 6, 3, 16, "PentiumII", },
{ 6, 5, 16, "PentiumII/Xeon", },
{ 6, 6, 16, "Celeron", },
{ 6, 7, 16, "PentiumIII/Xeon", },
{ 6, 8, 16, "PentiumIII/Xeon", },
{ 6, 0xB, 16, "PentiumIII/Xeon", },
{ 0xF, 1, 16, "P4", }, /* P4 */
{ 0xF, 2, 16, "PentiumIV/Xeon", },
{ 3, -1, 32, "386", }, /* family defaults */
{ 4, -1, 22, "486", },
{ 5, -1, 23, "P5", },
{ 6, -1, 16, "P6", },
{ 0xF, -1, 16, "P4", }, /* P4 */
{ -1, -1, 16, "unknown", }, /* total default */
};
/*
* The AMD processors all implement the CPUID instruction.
* The later ones also return the processor name via functions
* 0x80000002, 0x80000003 and 0x80000004 in registers AX, BX, CX
* and DX:
* K5 "AMD-K5(tm) Processor"
* K6 "AMD-K6tm w/ multimedia extensions"
* K6 3D "AMD-K6(tm) 3D processor"
* K6 3D+ ?
*/
static X86type x86amd[] =
{
{ 5, 0, 23, "AMD-K5", }, /* guesswork */
{ 5, 1, 23, "AMD-K5", }, /* guesswork */
{ 5, 2, 23, "AMD-K5", }, /* guesswork */
{ 5, 3, 23, "AMD-K5", }, /* guesswork */
{ 5, 4, 23, "AMD Geode GX1", }, /* guesswork */
{ 5, 5, 23, "AMD Geode GX2", }, /* guesswork */
{ 5, 6, 11, "AMD-K6", }, /* trial and error */
{ 5, 7, 11, "AMD-K6", }, /* trial and error */
{ 5, 8, 11, "AMD-K6-2", }, /* trial and error */
{ 5, 9, 11, "AMD-K6-III", },/* trial and error */
{ 5, 0xa, 23, "AMD Geode LX", }, /* guesswork */
{ 6, 1, 11, "AMD-Athlon", },/* trial and error */
{ 6, 2, 11, "AMD-Athlon", },/* trial and error */
{ 4, -1, 22, "Am486", }, /* guesswork */
{ 5, -1, 23, "AMD-K5/K6", }, /* guesswork */
{ 6, -1, 11, "AMD-Athlon", },/* guesswork */
{ 0xF, -1, 11, "AMD64", }, /* guesswork */
{ -1, -1, 11, "unknown", }, /* total default */
};
static X86type *cputype;
void
delay(int millisecs)
{
millisecs *= loopconst;
if(millisecs <= 0)
millisecs = 1;
aamloop(millisecs);
}
void
microdelay(int microsecs)
{
microsecs *= loopconst;
microsecs /= 1000;
if(microsecs <= 0)
microsecs = 1;
aamloop(microsecs);
}
extern void cpuid(char*, int*, int*);
X86type*
cpuidentify(void)
{
int family, model;
X86type *t;
char cpuidid[16];
int cpuidax, cpuiddx;
cpuid(cpuidid, &cpuidax, &cpuiddx);
if(strncmp(cpuidid, "AuthenticAMD", 12) == 0 ||
strncmp(cpuidid, "Geode by NSC", 12) == 0)
t = x86amd;
else
t = x86intel;
family = X86FAMILY(cpuidax);
model = X86MODEL(cpuidax);
if (0)
print("cpuidentify: cpuidax 0x%ux cpuiddx 0x%ux\n",
cpuidax, cpuiddx);
while(t->name){
if((t->family == family && t->model == model)
|| (t->family == family && t->model == -1)
|| (t->family == -1))
break;
t++;
}
if(t->name == nil)
panic("cpuidentify");
if(cpuiddx & 0x10){
havetsc = 1;
if(cpuiddx & 0x20)
wrmsr(0x10, 0);
}
return t;
}
void
clockinit(void)
{
uvlong a, b, cpufreq;
int loops, incr, x, y;
X86type *t;
/*
* set vector for clock interrupts
*/
setvec(VectorCLOCK, clockintr, 0);
t = cpuidentify();
/*
* set clock for 1/HZ seconds
*/
outb(Tmode, Load0|Square);
outb(T0cntr, (Freq/HZ)); /* low byte */
outb(T0cntr, (Freq/HZ)>>8); /* high byte */
/*
* 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;
}
/* find biggest loop that doesn't wrap */
incr = 16000000/(t->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.
*
*/
outb(Tmode, Latch0);
if(havetsc)
_cycles(&a);
x = inb(T0cntr);
x |= inb(T0cntr)<<8;
aamloop(loops);
outb(Tmode, Latch0);
if(havetsc)
_cycles(&b);
y = inb(T0cntr);
y |= inb(T0cntr)<<8;
x -= y;
if(x < 0)
x += Freq/HZ;
if(x > Freq/(3*HZ))
break;
}
/*
* figure out clock frequency and a loop multiplier for delay().
* counter goes at twice the frequency, once per transition,
* i.e., twice per square wave
*/
cpufreq = (vlong)loops*((t->aalcycles*2*Freq)/x);
loopconst = (cpufreq/1000)/t->aalcycles; /* AAM+LOOP's for 1 ms */
if(havetsc){
/* counter goes up by 2*Freq */
b = (b-a)<<1;
b *= Freq;
b /= x;
/*
* round to the nearest megahz
*/
cpumhz = (b+500000)/1000000L;
cpuhz = b;
}
else{
/*
* add in possible .5% error and convert to MHz
*/
cpumhz = (cpufreq + cpufreq/200)/1000000;
cpuhz = cpufreq;
}
if(debug){
int timeo;
print("%dMHz %s loop %d\n", cpumhz, t->name, loopconst);
print("tick...");
for(timeo = 0; timeo < 10; timeo++)
delay(1000);
print("tock...\n");
}
}