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

// SPDX-License-Identifier: GPL-2.0+
/*
 * (C) Copyright 2007-2011
 * Allwinner Technology Co., Ltd. <www.allwinnertech.com>
 * Tom Cubie <tangliang@allwinnertech.com>
 */

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

DECLARE_GLOBAL_DATA_PTR;

#define TIMER_MODE   (0x0 << 7)	/* continuous mode */
#define TIMER_DIV    (0x0 << 4)	/* pre scale 1 */
#define TIMER_SRC    (0x1 << 2)	/* osc24m */
#define TIMER_RELOAD (0x1 << 1)	/* reload internal value */
#define TIMER_EN     (0x1 << 0)	/* enable timer */

#define TIMER_CLOCK		(24 * 1000 * 1000)
#define COUNT_TO_USEC(x)	((x) / 24)
#define USEC_TO_COUNT(x)	((x) * 24)
#define TICKS_PER_HZ		(TIMER_CLOCK / CONFIG_SYS_HZ)
#define TICKS_TO_HZ(x)		((x) / TICKS_PER_HZ)

#define TIMER_LOAD_VAL		0xffffffff

#define TIMER_NUM		0	/* we use timer 0 */

/* read the 32-bit timer */
static ulong read_timer(void)
{
	struct sunxi_timer_reg *timers =
		(struct sunxi_timer_reg *)SUNXI_TIMER_BASE;
	struct sunxi_timer *timer = &timers->timer[TIMER_NUM];

	/*
	 * The hardware timer counts down, therefore we invert to
	 * produce an incrementing timer.
	 */
	return ~readl(&timer->val);
}

/* init timer register */
int timer_init(void)
{
	struct sunxi_timer_reg *timers =
		(struct sunxi_timer_reg *)SUNXI_TIMER_BASE;
	struct sunxi_timer *timer = &timers->timer[TIMER_NUM];

	writel(TIMER_LOAD_VAL, &timer->inter);
	writel(TIMER_MODE | TIMER_DIV | TIMER_SRC | TIMER_RELOAD | TIMER_EN,
	       &timer->ctl);

	return 0;
}

static ulong get_timer_masked(void)
{
	/* current tick value */
	ulong now = TICKS_TO_HZ(read_timer());

	if (now >= gd->arch.lastinc) {	/* normal (non rollover) */
		gd->arch.tbl += (now - gd->arch.lastinc);
	} else {
		/* rollover */
		gd->arch.tbl += (TICKS_TO_HZ(TIMER_LOAD_VAL)
				- gd->arch.lastinc) + now;
	}
	gd->arch.lastinc = now;

	return gd->arch.tbl;
}

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

/* delay x useconds */
void __udelay(unsigned long usec)
{
	long tmo = USEC_TO_COUNT(usec);
	ulong now, last = read_timer();

	while (tmo > 0) {
		now = read_timer();
		if (now > last)	/* normal (non rollover) */
			tmo -= now - last;
		else		/* rollover */
			tmo -= TIMER_LOAD_VAL - last + now;
		last = now;
	}
}

/*
 * 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;
}