u-boot/cpu/arm926ejs/at91/timer.c

/*
 * (C) Copyright 2007-2008
 * Stelian Pop <stelian.pop@leadtechdesign.com>
 * Lead Tech Design <www.leadtechdesign.com>
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */

#include <common.h>
#include <asm/arch/hardware.h>
#include <asm/arch/at91_pit.h>
#include <asm/arch/at91_pmc.h>
#include <asm/arch/clk.h>
#include <asm/arch/io.h>
#include <div64.h>

/*
 * We're using the AT91CAP9/SAM9 PITC in 32 bit mode, by
 * setting the 20 bit counter period to its maximum (0xfffff).
 */
#define TIMER_LOAD_VAL	0xfffff
#define READ_RESET_TIMER at91_sys_read(AT91_PIT_PIVR)
#define READ_TIMER at91_sys_read(AT91_PIT_PIIR)

static ulong timestamp;
static ulong lastinc;
static ulong timer_freq;

static inline unsigned long long tick_to_time(unsigned long long tick)
{
	tick *= CONFIG_SYS_HZ;
	do_div(tick, timer_freq);

	return tick;
}

static inline unsigned long long usec_to_tick(unsigned long long usec)
{
	usec *= timer_freq;
	do_div(usec, 1000000);

	return usec;
}

/* nothing really to do with interrupts, just starts up a counter. */
int timer_init(void)
{
	/*
	 * Enable PITC Clock
	 * The clock is already enabled for system controller in boot
	 */
	at91_sys_write(AT91_PMC_PCER, 1 << AT91_ID_SYS);

	/* Enable PITC */
	at91_sys_write(AT91_PIT_MR, TIMER_LOAD_VAL | AT91_PIT_PITEN);

	reset_timer_masked();

	timer_freq = get_mck_clk_rate() >> 4;

	return 0;
}

/*
 * timer without interrupts
 */
unsigned long long get_ticks(void)
{
	ulong now = READ_TIMER;

	if (now >= lastinc)	/* normal mode (non roll) */
		/* move stamp forward with absolut diff ticks */
		timestamp += (now - lastinc);
	else			/* we have rollover of incrementer */
		timestamp += (0xFFFFFFFF - lastinc) + now;
	lastinc = now;
	return timestamp;
}

void reset_timer_masked(void)
{
	/* reset time */
	lastinc = READ_TIMER; /* capture current incrementer value time */
	timestamp = 0; /* start "advancing" time stamp from 0 */
}

ulong get_timer_masked(void)
{
	return tick_to_time(get_ticks());
}

void udelay(unsigned long usec)
{
	unsigned long long tmp;
	ulong tmo;

	tmo = usec_to_tick(usec);
	tmp = get_ticks() + tmo;	/* get current timestamp */

	while (get_ticks() < tmp)	/* loop till event */
		 /*NOP*/;
}

void reset_timer(void)
{
	reset_timer_masked();
}

ulong get_timer(ulong base)
{
	return get_timer_masked () - base;
}

/*
 * 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)
{
	ulong tbclk;

	tbclk = CONFIG_SYS_HZ;
	return tbclk;
}