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  • /*
     * Cirrus Logic EP93xx timer support.
     *
     * Copyright (C) 2009, 2010
     * Matthias Kaehlcke <matthias@kaehlcke.net>
     *
     * Copyright (C) 2004, 2005
     * Cory T. Tusar, Videon Central, Inc., <ctusar@videon-central.com>
     *
     * Based on the original intr.c Cirrus Logic EP93xx Rev D. interrupt support,
     * author unknown.
     *
     * 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.,
     * 675 Mass Ave, Cambridge, MA 02139, USA.
     */
    
    #include <common.h>
    #include <linux/types.h>
    #include <asm/arch/ep93xx.h>
    #include <asm/io.h>
    
    
    #define TIMER_CLKSEL	(1 << 3)
    #define TIMER_MODE	(1 << 6)
    #define TIMER_ENABLE	(1 << 7)
    
    #define TIMER_FREQ	508469
    #define TIMER_LOAD_VAL	(TIMER_FREQ / CONFIG_SYS_HZ)
    
    static ulong timestamp;
    static ulong lastdec;
    
    static inline unsigned long clk_to_systicks(unsigned long clk_ticks)
    {
    
    	unsigned long long sys_ticks = (clk_ticks * CONFIG_SYS_HZ);
    	do_div(sys_ticks, TIMER_FREQ);
    
    	return (unsigned long)sys_ticks;
    
    }
    
    static inline unsigned long usecs_to_ticks(unsigned long usecs)
    {
    	unsigned long ticks;
    
    	if (usecs >= 1000) {
    		ticks = usecs / 1000;
    		ticks *= (TIMER_LOAD_VAL * CONFIG_SYS_HZ);
    		ticks /= 1000;
    	} else {
    		ticks = usecs * TIMER_LOAD_VAL * CONFIG_SYS_HZ;
    		ticks /= (1000 * 1000);
    	}
    
    	return ticks;
    }
    
    static inline unsigned long read_timer(void)
    {
    	struct timer_regs *timer = (struct timer_regs *)TIMER_BASE;
    
    	return readl(&timer->timer3.value);
    }
    
    /*
     * timer without interrupts
     */
    unsigned long long get_ticks(void)
    {
    	const unsigned long now = read_timer();
    
    	if (lastdec >= now) {
    		/* normal mode */
    		timestamp += lastdec - now;
    	} else {
    		/* we have an overflow ... */
    		timestamp += lastdec + TIMER_LOAD_VAL - now;
    	}
    
    	lastdec = now;
    
    	return timestamp;
    }
    
    unsigned long get_timer_masked(void)
    {
    	return clk_to_systicks(get_ticks());
    }
    
    unsigned long get_timer(unsigned long base)
    {
    	return get_timer_masked() - base;
    }
    
    void reset_timer_masked(void)
    {
    	lastdec = read_timer();
    	timestamp = 0;
    }
    
    void reset_timer(void)
    {
    	reset_timer_masked();
    }
    
    void set_timer(unsigned long t)
    {
    	timestamp = t;
    }
    
    void __udelay(unsigned long usec)
    {
    	const unsigned long ticks = usecs_to_ticks(usec);
    	const unsigned long target = clk_to_systicks(ticks) + get_timer(0);
    
    	while (get_timer_masked() < target)
    		/* noop */;
    }
    
    void udelay_masked(unsigned long usec)
    {
    	const unsigned long ticks = usecs_to_ticks(usec);
    	const unsigned long target = clk_to_systicks(ticks) + get_timer(0);
    
    	reset_timer_masked();
    
    	while (get_timer_masked() < target)
    		/* noop */;
    }
    
    int timer_init(void)
    {
    	struct timer_regs *timer = (struct timer_regs *)TIMER_BASE;
    
    	/* use timer 3 with 508KHz and free running */
    	writel(TIMER_CLKSEL, &timer->timer3.control);
    
    	/* auto load, manual update of Timer 3 */
    	lastdec = TIMER_LOAD_VAL;
    	writel(TIMER_LOAD_VAL, &timer->timer3.load);
    
    	/* Enable the timer and periodic mode */
    	writel(TIMER_ENABLE | TIMER_MODE | TIMER_CLKSEL,
    		&timer->timer3.control);
    
    	reset_timer_masked();
    
    	return 0;
    }
    
    /*
     * This function is derived from PowerPC code (timebase clock frequency).
     * On ARM it returns the number of timer ticks per second.
     */
    unsigned long get_tbclk(void)
    {
    	return CONFIG_SYS_HZ;
    }