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TIMER: Provide an internal calibrated clock when none is otherwise available.

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In the event that there are no active clock devices, no instruction
rate calibration will be performed.  This is more likely on simpler
simulators which don't have a full spectrum of standard devices or
possibly when a clock device exists but its use is optional and thus
sometimes it may be disabled.
This commit is contained in:
Mark Pizzolato 2016-01-28 08:00:41 -08:00
parent 21b31fc3a8
commit 00e8c80c7b
1 changed files with 29 additions and 2 deletions
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31
sim_timer.c
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@ -555,7 +555,8 @@ static uint32 rtc_elapsed[SIM_NTIMERS] = { 0 }; /* sec since init */
static uint32 rtc_calibrations[SIM_NTIMERS] = { 0 }; /* calibration count */
static double rtc_clock_skew_max[SIM_NTIMERS] = { 0 }; /* asynchronous max skew */
UNIT sim_timer_units[SIM_NTIMERS+1]; /* one for each timer and one for throttle */
UNIT sim_timer_units[SIM_NTIMERS+2]; /* one for each timer and one for throttle */
/* plus one for an internal clock if no clocks are registered */
void sim_rtcn_init_all (void)
@ -896,7 +897,7 @@ MTAB sim_timer_mod[] = {
DEVICE sim_timer_dev = {
"TIMER", sim_timer_units, sim_timer_reg, sim_timer_mod,
SIM_NTIMERS+1, 0, 0, 0, 0, 0,
SIM_NTIMERS+2, 0, 0, 0, 0, 0,
NULL, NULL, NULL, NULL, NULL, NULL,
NULL, DEV_DEBUG | DEV_NOSAVE, 0, sim_timer_debug};
@ -1376,8 +1377,34 @@ return NULL;
#endif /* defined(SIM_ASYNCH_IO) && defined(SIM_ASYNCH_CLOCKS) */
/*
In the event that there are no active clock devices, no instruction
rate calibration will be performed. This is more likely on simpler
simulators which don't have a full spectrum of standard devices or
possibly when a clock device exists but its use is optional.
To solve this we merely run an internal clock at 50Hz.
*/
#define CLK_TPS 50
static sim_timer_clock_tick_svc (UNIT *uptr)
{
sim_rtcn_calb (CLK_TPS, SIM_NTIMERS-1);
sim_activate_after (uptr, 1000000/CLK_TPS); /* reactivate unit */
}
void sim_start_timer_services (void)
{
uint32 i;
for (i = 0; i < SIM_NTIMERS; i++)
if (rtc_initd[i] != 0)
break;
if (i == SIM_NTIMERS) { /* No clocks have signed in. */
/* setup internal clock */
sim_timer_units[SIM_NTIMERS+1].action = &sim_timer_clock_tick_svc;
sim_rtcn_init_unit (&sim_timer_units[SIM_NTIMERS+1], 5000, SIM_NTIMERS-1);
sim_activate_abs (&sim_timer_units[SIM_NTIMERS+1], 5000);
}
#if defined(SIM_ASYNCH_IO) && defined(SIM_ASYNCH_CLOCKS)
pthread_mutex_lock (&sim_timer_lock);
if (sim_asynch_enabled && sim_asynch_timer) {