/**
* Detects the local APIC reference bus clock. The only sure-fire way to do
* this is to depend on some other absolute timing source. This function uses
* the CPU's cycle counter and the previously detected CPU clock frequency.
*
* NOTE: This assumes that the CPU's clock frequency has already been detected.
* (i.e., cpu_info[cpu_id()].arch.tsc_khz has been initialized.
*/
unsigned int __init
lapic_calibrate_timer(void)
{
const unsigned int tick_count = 100000000;
cycles_t tsc_start, tsc_now;
uint32_t apic_start, apic_now;
unsigned int apic_Hz;
/* Start the APIC counter running for calibration */
lapic_set_timer_count(4000000000);
apic_start = apic_read(APIC_TMCCT);
tsc_start = get_cycles_sync();
/* Spin until enough ticks for a meaningful result have elapsed */
do {
apic_now = apic_read(APIC_TMCCT);
tsc_now = get_cycles_sync();
} while ( ((tsc_now - tsc_start) < tick_count) &&
((apic_start - apic_now) < tick_count) );
apic_Hz = (apic_start - apic_now) * 1000L *
cpu_info[this_cpu].arch.tsc_khz / (tsc_now - tsc_start);
lapic_stop_timer();
return (apic_Hz / 1000);
}
PUBLIC int init_local_timer(unsigned freq)
{
#ifdef USE_APIC
/* if we know the address, lapic is enabled and we should use it */
if (lapic_addr) {
unsigned cpu = cpuid;
tsc_per_ms[cpu] = div64u(cpu_get_freq(cpu), 1000);
lapic_set_timer_one_shot(1000000/system_hz);
} else
{
BOOT_VERBOSE(printf("Initiating legacy i8253 timer\n"));
#else
{
#endif
init_8253A_timer(freq);
estimate_cpu_freq();
/* always only 1 cpu in the system */
tsc_per_ms[0] = div64u(cpu_get_freq(0), 1000);
}
return 0;
}
PUBLIC void stop_local_timer(void)
{
#ifdef USE_APIC
if (lapic_addr) {
lapic_stop_timer();
apic_eoi();
} else
#endif
{
stop_8253A_timer();
}
}
PUBLIC void restart_local_timer(void)
{
#ifdef USE_APIC
if (lapic_addr) {
lapic_restart_timer();
}
#endif
}
PUBLIC int register_local_timer_handler(const irq_handler_t handler)
{
#ifdef USE_APIC
if (lapic_addr) {
/* Using APIC, it is configured in apic_idt_init() */
BOOT_VERBOSE(printf("Using LAPIC timer as tick source\n"));
} else
#endif
{
/* Using PIC, Initialize the CLOCK's interrupt hook. */
pic_timer_hook.proc_nr_e = NONE;
pic_timer_hook.irq = CLOCK_IRQ;
put_irq_handler(&pic_timer_hook, CLOCK_IRQ, handler);
}
return 0;
}
PUBLIC void cycles_accounting_init(void)
{
#ifdef CONFIG_SMP
unsigned cpu = cpuid;
#endif
read_tsc_64(get_cpu_var_ptr(cpu, tsc_ctr_switch));
make_zero64(get_cpu_var(cpu, cpu_last_tsc));
make_zero64(get_cpu_var(cpu, cpu_last_idle));
}