delay_tsc.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <arch/cpu.h>
#include <cpu/x86/tsc.h>
#include <delay.h>
#include <thread.h>
 
void init_timer(void)
{
        (void)tsc_freq_mhz();
}
 
void udelay(unsigned int us)
{
        unsigned long long start;
        unsigned long long current;
        unsigned long long clocks;
 
        if (!thread_yield_microseconds(us))
                return;
 
        start = rdtscll();
        clocks = us;
        clocks *= tsc_freq_mhz();
        current = rdtscll();
        while ((current - start) < clocks) {
                cpu_relax();
                current = rdtscll();
        }
}
 
#if CONFIG(TSC_MONOTONIC_TIMER)
#include <timer.h>
 
static struct monotonic_counter {
        int initialized;
        struct mono_time time;
        uint64_t last_value;
} mono_counter;
 
void timer_monotonic_get(struct mono_time *mt)
{
        uint64_t current_tick;
        uint64_t ticks_elapsed;
        unsigned long ticks_per_usec;
 
        if (!mono_counter.initialized) {
                init_timer();
                mono_counter.last_value = rdtscll();
                mono_counter.initialized = 1;
        }
 
        current_tick = rdtscll();
        ticks_elapsed = current_tick - mono_counter.last_value;
        ticks_per_usec = tsc_freq_mhz();
 
        /* Update current time and tick values only if a full tick occurred. */
        if (ticks_elapsed >= ticks_per_usec) {
                uint64_t usecs_elapsed;
 
                usecs_elapsed = ticks_elapsed / ticks_per_usec;
                mono_time_add_usecs(&mono_counter.time, (long)usecs_elapsed);
                mono_counter.last_value = current_tick;
        }
 
        /* Save result. */
        *mt = mono_counter.time;
}
#endif