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When TSC is unavailable, broken or disabled and the current timecounter has

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better quality than i8254 timer, use it for DELAY(9).
This commit is contained in:
jkim 2011-03-14 22:05:59 +00:00
parent 45a4292831
commit 36e15e1609
1 changed files with 43 additions and 10 deletions
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53
sys/x86/isa/clock.c
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@ -245,6 +245,42 @@ getit(void)
return ((high << 8) | low);
}
static __inline void
delay_tsc(int n)
{
uint64_t start, end, now;
sched_pin();
start = rdtsc();
end = start + (tsc_freq * n) / 1000000;
do {
cpu_spinwait();
now = rdtsc();
} while (now < end || (now > start && end < start));
sched_unpin();
}
static __inline void
delay_timecounter(struct timecounter *tc, int n)
{
uint64_t end, now;
u_int last, mask, u;
mask = tc->tc_counter_mask;
last = tc->tc_get_timecount(tc) & mask;
end = tc->tc_frequency * n / 1000000;
now = 0;
do {
cpu_spinwait();
u = tc->tc_get_timecount(tc) & mask;
if (u < last)
now += mask - last + u + 1;
else
now += u - last;
last = u;
} while (now < end);
}
/*
* Wait "n" microseconds.
* Relies on timer 1 counting down from (i8254_freq / hz)
@ -253,6 +289,7 @@ getit(void)
void
DELAY(int n)
{
struct timecounter *tc;
int delta, prev_tick, tick, ticks_left;
#ifdef DELAYDEBUG
@ -262,16 +299,12 @@ DELAY(int n)
#endif
if (tsc_freq != 0) {
uint64_t start, end, now;
sched_pin();
start = rdtsc();
end = start + (tsc_freq * n) / 1000000;
do {
cpu_spinwait();
now = rdtsc();
} while (now < end || (now > start && end < start));
sched_unpin();
delay_tsc(n);
return;
}
tc = timecounter;
if (tc->tc_quality > 0) {
delay_timecounter(tc, n);
return;
}
#ifdef DELAYDEBUG