u-boot/arch/arm/mach-omap2/timer.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * (C) Copyright 2008
 * Texas Instruments
 *
 * Richard Woodruff <r-woodruff2@ti.com>
 * Syed Moahmmed Khasim <khasim@ti.com>
 *
 * (C) Copyright 2002
 * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
 * Marius Groeger <mgroeger@sysgo.de>
 * Alex Zuepke <azu@sysgo.de>
 *
 * (C) Copyright 2002
 * Gary Jennejohn, DENX Software Engineering, <garyj@denx.de>
 */

#include <common.h>
#include <init.h>
#include <time.h>
#include <asm/global_data.h>
#include <asm/io.h>
#include <asm/arch/cpu.h>
#include <asm/arch/clock.h>
#include <asm/omap_common.h>
#include <linux/delay.h>

DECLARE_GLOBAL_DATA_PTR;

static struct gptimer *timer_base = (struct gptimer *)CFG_SYS_TIMERBASE;
static ulong get_timer_masked(void);

/*
 * Nothing really to do with interrupts, just starts up a counter.
 */

#define TIMER_CLOCK		(V_SCLK / (2 << SYS_PTV))
#define TIMER_OVERFLOW_VAL	0xffffffff
#define TIMER_LOAD_VAL		0

int timer_init(void)
{
	/* start the counter ticking up, reload value on overflow */
	writel(TIMER_LOAD_VAL, &timer_base->tldr);
	/* enable timer */
	writel((SYS_PTV << 2) | TCLR_PRE | TCLR_AR | TCLR_ST,
		&timer_base->tclr);

	return 0;
}

/*
 * timer without interrupts
 */
ulong get_timer(ulong base)
{
	return get_timer_masked() - base;
}

/* delay x useconds */
void __udelay(unsigned long usec)
{
	long tmo = usec * (TIMER_CLOCK / 1000) / 1000;
	unsigned long now, last = readl(&timer_base->tcrr);

	while (tmo > 0) {
		now = readl(&timer_base->tcrr);
		if (last > now) /* count up timer overflow */
			tmo -= TIMER_OVERFLOW_VAL - last + now + 1;
		else
			tmo -= now - last;
		last = now;
	}
}

static ulong get_timer_masked(void)
{
	/* current tick value */
	ulong now = readl(&timer_base->tcrr) / (TIMER_CLOCK / CONFIG_SYS_HZ);

	if (now >= gd->arch.lastinc) {	/* normal mode (non roll) */
		/* move stamp fordward with absoulte diff ticks */
		gd->arch.tbl += (now - gd->arch.lastinc);
	} else {	/* we have rollover of incrementer */
		gd->arch.tbl += ((TIMER_OVERFLOW_VAL / (TIMER_CLOCK /
				CONFIG_SYS_HZ)) - gd->arch.lastinc) + now;
	}
	gd->arch.lastinc = now;
	return gd->arch.tbl;
}

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