ref: bf7e8777f391caa82705a0b64709a95672d2632c
dir: /sys/src/9/teg2/clock.c/
/*
* cortex-a clocks; excludes tegra 2 SoC clocks
*
* cortex-a processors include private `global' and local timers
* at soc.scu + 0x200 (global) and + 0x600 (local).
* the global timer is a single count-up timer shared by all cores
* but with per-cpu comparator and auto-increment registers.
* a local count-down timer can be used as a watchdog.
*
* v7 arch provides a 32-bit count-up cycle counter (at about 1GHz in our case)
* but it's unsuitable as our source of fastticks, because it stops advancing
* when the cpu is suspended by WFI.
*/
#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "arm.h"
enum {
Debug = 0,
Basetickfreq = Mhz, /* soc.µs rate in Hz */
/* the local timers seem to run at half the expected rate */
Clockfreqbase = 250*Mhz / 2, /* private timer rate (PERIPHCLK/2) */
Tcycles = Clockfreqbase / HZ, /* cycles per clock tick */
MinPeriod = Tcycles / 100,
MaxPeriod = Tcycles,
Dogtimeout = Dogsectimeout * Clockfreqbase,
};
typedef struct Ltimer Ltimer;
typedef struct Pglbtmr Pglbtmr;
typedef struct Ploctmr Ploctmr;
/*
* cortex-a private-intr local timer registers. all cpus see their
* own local timers at the same base address.
*/
struct Ltimer {
ulong load; /* new value + 1 */
ulong cnt; /* counts down */
ulong ctl;
ulong isr;
/* watchdog only */
ulong wdrst;
ulong wddis; /* wo */
ulong _pad0[2];
};
struct Ploctmr {
Ltimer loc;
Ltimer wd;
};
enum {
/* ctl bits */
Tmrena = 1<<0, /* timer enabled */
Wdogena = Tmrena, /* watchdog enabled */
Xreload = 1<<1, /* reload on intr; periodic interrupts */
Tintena = 1<<2, /* enable irq 29 at cnt==0 (30 for watchdog) */
Wdog = 1<<3, /* watchdog, not timer, mode */
Xsclrshift = 8,
Xsclrmask = MASK(8),
/* isr bits */
Xisrclk = 1<<0, /* write to clear */
/* wdrst bits */
Wdrst = 1<<0,
/* wddis values */
Wdon = 1,
Wdoff1 = 0x12345678, /* send these two to switch to timer mode */
Wdoff2 = 0x87654321,
};
/* cortex-a private-intr globl timer registers */
struct Pglbtmr {
ulong cnt[2]; /* counts up; little-endian uvlong */
ulong ctl;
ulong isr;
ulong cmp[2]; /* little-endian uvlong */
ulong inc;
};
enum {
/* unique ctl bits (otherwise see X* above) */
Gcmp = 1<<1,
// Gtintena= 1<<2, /* enable irq 27 */
Gincr = 1<<3,
};
/*
* until 5[cl] inline vlong ops, avoid them where possible,
* they are currently slow function calls.
*/
typedef union Vlong Vlong;
union Vlong {
uvlong uvl;
struct { /* little-endian */
ulong low;
ulong high;
};
};
static int fired;
static int ticking[MAXMACH];
/* no lock is needed to update our local timer. splhi keeps it tight. */
static void
setltimer(Ltimer *tn, ulong ticks)
{
int s;
assert(ticks <= Clockfreqbase);
s = splhi();
tn->load = ticks - 1;
coherence();
tn->ctl = Tmrena | Tintena | Xreload;
coherence();
splx(s);
}
static void
ckstuck(int cpu, long myticks, long histicks)
{
if (labs(histicks - myticks) > HZ) {
// iprint("cpu%d: clock ticks %ld (vs myticks %ld cpu0 %ld); "
// "apparently stopped\n",
// cpu, histicks, myticks, MACHP(0)->ticks);
if (!ticking[cpu])
panic("cpu%d: clock not interrupting", cpu);
}
}
static void
mpclocksanity(void)
{
int cpu, mycpu;
long myticks, histicks;
if (conf.nmach <= 1 || active.exiting || navailcpus == 0)
return;
mycpu = m->machno;
myticks = m->ticks;
if (myticks == HZ)
ticking[mycpu] = 1;
if (myticks < 5*HZ)
return;
for (cpu = 0; cpu < navailcpus; cpu++) {
if (cpu == mycpu)
continue;
histicks = MACHP(cpu)->ticks;
if (myticks == 5*HZ || histicks > 1)
ckstuck(cpu, myticks, histicks);
}
}
static void
clockintr(Ureg* ureg, void *arg)
{
Ltimer *wd, *tn;
Ploctmr *lt;
lt = (Ploctmr *)arg;
tn = <->loc;
tn->isr = Xisrclk;
coherence();
timerintr(ureg, 0);
#ifdef watchdog_not_bloody_useless
/* appease the dogs */
wd = <->wd;
if (wd->cnt == 0 &&
(wd->ctl & (Wdog | Wdogena | Tintena)) == (Wdog | Wdogena))
panic("cpu%d: zero watchdog count but no system reset",
m->machno);
wd->load = Dogtimeout - 1;
coherence();
#endif
SET(wd); USED(wd);
tegclockintr();
mpclocksanity();
}
void
clockprod(Ureg *ureg)
{
Ltimer *tn;
timerintr(ureg, 0);
tegclockintr();
if (m->machno != 0) { /* cpu1 gets stuck */
tn = &((Ploctmr *)soc.loctmr)->loc;
setltimer(tn, Tcycles);
}
}
static void
clockreset(Ltimer *tn)
{
if (probeaddr((uintptr)tn) < 0)
panic("no clock at %#p", tn);
tn->ctl = 0;
coherence();
}
void
watchdogoff(Ltimer *wd)
{
wd->ctl &= ~Wdogena;
coherence();
wd->wddis = Wdoff1;
coherence();
wd->wddis = Wdoff2;
coherence();
}
/* clear any pending watchdog intrs or causes */
void
wdogclrintr(Ltimer *wd)
{
#ifdef watchdog_not_bloody_useless
wd->isr = Xisrclk;
coherence();
wd->wdrst = Wdrst;
coherence();
#endif
USED(wd);
}
/*
* stop clock interrupts on this cpu and disable the local watchdog timer,
* and, if on cpu0, shutdown the shared tegra2 watchdog timer.
*/
void
clockshutdown(void)
{
Ploctmr *lt;
lt = (Ploctmr *)soc.loctmr;
clockreset(<->loc);
watchdogoff(<->wd);
tegclockshutdown();
}
enum {
Instrs = 10*Mhz,
};
/* we assume that perfticks are microseconds */
static long
issue1loop(void)
{
register int i;
long st;
i = Instrs;
st = perfticks();
do {
--i; --i; --i; --i; --i; --i; --i; --i; --i; --i;
--i; --i; --i; --i; --i; --i; --i; --i; --i; --i;
--i; --i; --i; --i; --i; --i; --i; --i; --i; --i;
--i; --i; --i; --i; --i; --i; --i; --i; --i; --i;
--i; --i; --i; --i; --i; --i; --i; --i; --i; --i;
--i; --i; --i; --i; --i; --i; --i; --i; --i; --i;
--i; --i; --i; --i; --i; --i; --i; --i; --i; --i;
--i; --i; --i; --i; --i; --i; --i; --i; --i; --i;
--i; --i; --i; --i; --i; --i; --i; --i; --i; --i;
--i; --i; --i; --i; --i; --i; --i; --i; --i;
} while(--i >= 0);
return perfticks() - st;
}
static long
issue2loop(void)
{
register int i, j;
long st;
i = Instrs / 2; /* j gets half the decrements */
j = 0;
st = perfticks();
do {
--j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
--i; --j; --i; --j; --i; --j; --i; --j; --i; --j;
} while(--i >= 0);
return perfticks() - st;
}
/* estimate instructions/s. */
static void
guessmips(long (*loop)(void), char *lab)
{
int s;
long tcks;
do {
s = splhi();
tcks = loop();
splx(s);
if (tcks < 0)
iprint("again...");
} while (tcks < 0);
/*
* Instrs instructions took tcks ticks @ Basetickfreq Hz.
* round the result.
*/
s = (((vlong)Basetickfreq * Instrs) / tcks + 500000) / 1000000;
if (Debug)
iprint("%ud mips (%s-issue)", s, lab);
USED(s);
}
void
wdogintr(Ureg *, void *ltmr)
{
#ifdef watchdog_not_bloody_useless
Ltimer *wd;
wd = ltmr;
fired++;
wdogclrintr(wd);
#endif
USED(ltmr);
}
static void
ckcounting(Ltimer *lt)
{
ulong old;
old = lt->cnt;
if (old == lt->cnt)
delay(1);
if (old == lt->cnt)
panic("cpu%d: watchdog timer not counting down", m->machno);
}
/* test fire with interrupt to see that it's working */
static void
ckwatchdog(Ltimer *wd)
{
#ifdef watchdog_not_bloody_useless
int s;
fired = 0;
wd->load = Tcycles - 1;
coherence();
/* Tintena is supposed to be ignored in watchdog mode */
wd->ctl |= Wdogena | Tintena;
coherence();
ckcounting(wd);
s = spllo();
delay(2 * 1000/HZ);
splx(s);
if (!fired)
/* useless local watchdog */
iprint("cpu%d: local watchdog failed to interrupt\n", m->machno);
/* clean up */
wd->ctl &= ~Wdogena;
coherence();
#endif
USED(wd);
}
static void
startwatchdog(void)
{
#ifdef watchdog_not_bloody_useless
Ltimer *wd;
Ploctmr *lt;
lt = (Ploctmr *)soc.loctmr;
wd = <->wd;
watchdogoff(wd);
wdogclrintr(wd);
irqenable(Wdtmrirq, wdogintr, wd, "watchdog");
ckwatchdog(wd);
/* set up for normal use, causing reset */
wd->ctl &= ~Tintena; /* reset, don't interrupt */
coherence();
wd->ctl |= Wdog;
coherence();
wd->load = Dogtimeout - 1;
coherence();
wd->ctl |= Wdogena;
coherence();
ckcounting(wd);
#endif
}
static void
clock0init(Ltimer *tn)
{
int s;
ulong old, fticks;
/*
* calibrate fastclock
*/
s = splhi();
tn->load = ~0ul >> 1;
coherence();
tn->ctl = Tmrena;
coherence();
old = perfticks();
fticks = tn->cnt;
delay(1);
fticks = abs(tn->cnt - fticks);
old = perfticks() - old;
splx(s);
if (Debug)
iprint("cpu%d: fastclock %ld/%ldµs = %ld fastticks/µs (MHz)\n",
m->machno, fticks, old, (fticks + old/2 - 1) / old);
USED(fticks, old);
if (Debug)
iprint("cpu%d: ", m->machno);
guessmips(issue1loop, "single");
if (Debug)
iprint(", ");
guessmips(issue2loop, "dual");
if (Debug)
iprint("\n");
/*
* m->delayloop should be the number of delay loop iterations
* needed to consume 1 ms. 2 is instr'ns in the delay loop.
*/
m->delayloop = m->cpuhz / (1000 * 2);
// iprint("cpu%d: m->delayloop = %lud\n", m->machno, m->delayloop);
tegclock0init();
}
/*
* the local timer is the interrupting timer and does not
* participate in measuring time. It is initially set to HZ.
*/
void
clockinit(void)
{
ulong old;
Ltimer *tn;
Ploctmr *lt;
clockshutdown();
/* turn my cycle counter on */
cpwrsc(0, CpCLD, CpCLDena, CpCLDenacyc, 1<<31);
/* turn all my counters on and clear my cycle counter */
cpwrsc(0, CpCLD, CpCLDena, CpCLDenapmnc, 1<<2 | 1);
/* let users read my cycle counter directly */
cpwrsc(0, CpCLD, CpCLDuser, CpCLDenapmnc, 1);
/* verify µs counter sanity */
tegclockinit();
lt = (Ploctmr *)soc.loctmr;
tn = <->loc;
if (m->machno == 0)
irqenable(Loctmrirq, clockintr, lt, "clock");
else
intcunmask(Loctmrirq);
/*
* verify sanity of local timer
*/
tn->load = Clockfreqbase / 1000;
tn->isr = Xisrclk;
coherence();
tn->ctl = Tmrena;
coherence();
old = tn->cnt;
delay(5);
/* m->ticks won't be incremented here because timersinit hasn't run. */
if (tn->cnt == old)
panic("cpu%d: clock not ticking at all", m->machno);
else if ((long)tn->cnt > 0)
panic("cpu%d: clock ticking slowly", m->machno);
if (m->machno == 0)
clock0init(tn);
/* if pci gets stuck, maybe one of the many watchdogs will nuke us. */
startwatchdog();
/*
* desynchronize the processor clocks so that they all don't
* try to resched at the same time.
*/
delay(m->machno*2);
setltimer(tn, Tcycles);
}
/* our fastticks are at 1MHz (Basetickfreq), so the conversion is trivial. */
ulong
µs(void)
{
return fastticks2us(fastticks(nil));
}
/* Tval is supposed to be in fastticks units. */
void
timerset(Tval next)
{
int s;
long offset;
Ltimer *tn;
tn = &((Ploctmr *)soc.loctmr)->loc;
s = splhi();
offset = fastticks2us(next - fastticks(nil));
/* offset is now in µs (MHz); convert to Clockfreqbase Hz. */
offset *= Clockfreqbase / Mhz;
if(offset < MinPeriod)
offset = MinPeriod;
else if(offset > MaxPeriod)
offset = MaxPeriod;
setltimer(tn, offset);
splx(s);
}
static ulong
cpucycles(void) /* cpu clock rate, except when waiting for intr (unused) */
{
ulong v;
/* reads 32-bit cycle counter (counting up) */
// v = cprdsc(0, CpCLD, CpCLDcyc, 0);
v = getcyc(); /* fast asm */
/* keep it non-negative; prevent m->fastclock ever going to 0 */
return v == 0? 1: v;
}
long
lcycles(void)
{
return perfticks();
}
uvlong
fastticks(uvlong *hz)
{
int s;
ulong newticks;
Vlong *fcp;
if(hz)
*hz = Basetickfreq;
fcp = (Vlong *)&m->fastclock;
/* avoid reentry on interrupt or trap, to prevent recursion */
s = splhi();
newticks = perfticks();
if(newticks < fcp->low) /* low word must have wrapped */
fcp->high++;
fcp->low = newticks;
splx(s);
if (fcp->low == 0 && fcp->high == 0 && m->ticks > HZ/10)
panic("fastticks: zero m->fastclock; ticks %lud fastclock %#llux",
m->ticks, m->fastclock);
return m->fastclock;
}
void
microdelay(int l)
{
for (l = l * (vlong)m->delayloop / 1000; --l >= 0; )
;
}
void
delay(int l)
{
int i, d;
d = m->delayloop;
while(--l >= 0)
for (i = d; --i >= 0; )
;
}