board/armltd/integratorap/timer.c

/*
 * (C) Copyright 2002
 * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
 * Marius Groeger <mgroeger@sysgo.de>
 *
 * (C) Copyright 2002
 * David Mueller, ELSOFT AG, <d.mueller@elsoft.ch>
 *
 * (C) Copyright 2003
 * Texas Instruments, <www.ti.com>
 * Kshitij Gupta <Kshitij@ti.com>
 *
 * (C) Copyright 2004
 * ARM Ltd.
 * Philippe Robin, <philippe.robin@arm.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>

/* The Integrator/AP timer1 is clocked at 24MHz
 * can be divided by 16 or 256
 * and is a 16-bit counter
 */
/* U-Boot expects a 32 bit timer running at CONFIG_SYS_HZ*/
static ulong timestamp;		/* U-Boot ticks since startup	      */
static ulong total_count = 0;	/* Total timer count		      */
static ulong lastdec;		/* Timer reading at last call	      */
static ulong div_clock	 = 256; /* Divisor applied to the timer clock */
static ulong div_timer	 = 1;	/* Divisor to convert timer reading
				 * change to U-Boot ticks
				 */
/* CONFIG_SYS_HZ = CONFIG_SYS_HZ_CLOCK/(div_clock * div_timer) */

#define TIMER_LOAD_VAL 0x0000FFFFL
#define READ_TIMER ((*(volatile ulong *)(CONFIG_SYS_TIMERBASE+4)) & 0x0000FFFFL)

/* all function return values in U-Boot ticks i.e. (1/CONFIG_SYS_HZ) sec
 *  - unless otherwise stated
 */

/* starts a counter
 * - the Integrator/AP timer issues an interrupt
 *   each time it reaches zero
 */
int timer_init (void)
{
	/* Load timer with initial value */
	*(volatile ulong *)(CONFIG_SYS_TIMERBASE + 0) = TIMER_LOAD_VAL;
	/* Set timer to be
	 *	enabled		  1
	 *	free-running	  0
	 *	XX		 00
	 *	divider 256	 10
	 *	XX		 00
	 */
	*(volatile ulong *)(CONFIG_SYS_TIMERBASE + 8) = 0x00000088;
	total_count = 0;
	/* init the timestamp and lastdec value */
	reset_timer_masked();

	div_timer  = CONFIG_SYS_HZ_CLOCK / CONFIG_SYS_HZ;
	div_timer /= div_clock;

	return (0);
}

/*
 * timer without interrupts
 */
void reset_timer (void)
{
	reset_timer_masked ();
}

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

void set_timer (ulong ticks)
{
	timestamp = ticks;
	total_count = ticks * div_timer;
	reset_timer_masked();
}

/* delay x useconds */
void udelay (unsigned long usec)
{
	ulong tmo, tmp;

	/* Convert to U-Boot ticks */
	tmo  = usec * CONFIG_SYS_HZ;
	tmo /= (1000000L);

	tmp  = get_timer_masked();	/* get current timestamp */
	tmo += tmp;			/* wake up timestamp	 */

	while (get_timer_masked () < tmo) { /* loop till event */
		/*NOP*/;
	}
}

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

/* converts the timer reading to U-Boot ticks	       */
/* the timestamp is the number of ticks since reset    */
/* This routine does not detect wraps unless called regularly
   ASSUMES a call at least every 16 seconds to detect every reload */
ulong get_timer_masked (void)
{
	ulong now = READ_TIMER;		/* current count */

	if (now > lastdec) {
		/* Must have wrapped */
		total_count += lastdec + TIMER_LOAD_VAL + 1 - now;
	} else {
		total_count += lastdec - now;
	}
	lastdec	  = now;
	timestamp = total_count/div_timer;

	return timestamp;
}

/* waits specified delay value and resets timestamp */
void udelay_masked (unsigned long usec)
{
	udelay(usec);
}

/*
 * 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);
}

/*
 * Return the timebase clock frequency
 * i.e. how often the timer decrements
 */
ulong get_tbclk (void)
{
	return CONFIG_SYS_HZ_CLOCK/div_clock;
}