u-boot/arch/mips/cpu/mips32/time.c

/*
 * (C) Copyright 2003
 * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

#include <common.h>
#include <asm/mipsregs.h>

static unsigned long timestamp;

/* how many counter cycles in a jiffy */
#define CYCLES_PER_JIFFY	\
	(CONFIG_SYS_MIPS_TIMER_FREQ + CONFIG_SYS_HZ / 2) / CONFIG_SYS_HZ

/*
 * timer without interrupts
 */

int timer_init(void)
{
	/* Set up the timer for the first expiration. */
	write_c0_compare(read_c0_count() + CYCLES_PER_JIFFY);

	return 0;
}

ulong get_timer(ulong base)
{
	unsigned int count;
	unsigned int expirelo = read_c0_compare();

	/* Check to see if we have missed any timestamps. */
	count = read_c0_count();
	while ((count - expirelo) < 0x7fffffff) {
		expirelo += CYCLES_PER_JIFFY;
		timestamp++;
	}
	write_c0_compare(expirelo);

	return timestamp - base;
}

void __udelay(unsigned long usec)
{
	unsigned int tmo;

	tmo = read_c0_count() + (usec * (CONFIG_SYS_MIPS_TIMER_FREQ / 1000000));
	while ((tmo - read_c0_count()) < 0x7fffffff)
		/*NOP*/;
}

/*
 * This function is derived from PowerPC code (read timebase as long long).
 * On MIPS it just returns the timer value.
 */
unsigned long long get_ticks(void)
{
	return get_timer(0);
}

/*
 * This function is derived from PowerPC code (timebase clock frequency).
 * On MIPS it returns the number of timer ticks per second.
 */
ulong get_tbclk(void)
{
	return CONFIG_SYS_HZ;
}