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/*

 *  linux/arch/arm/mach-ebsa110/time.c

 *

 *  Copyright (C) 2001 Russell King

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */

#include <linux/sched.h>

#include <linux/init.h>

#include <asm/io.h>

#define PIT_CTRL                (PIT_BASE + 0x0d)

#define PIT_T2                  (PIT_BASE + 0x09)

#define PIT_T1                  (PIT_BASE + 0x05)

#define PIT_T0                  (PIT_BASE + 0x01)

/*

 * This is the rate at which your MCLK signal toggles (in Hz)

 * This was measured on a 10 digit frequency counter sampling

 * over 1 second.

 */

#define MCLK    47894000

/*

 * This is the rate at which the PIT timers get clocked

 */

#define CLKBY7  (MCLK / 7)

/*

 * If CLKBY7 is larger than this, then we must do software

 * division of the timer interrupt.

 */

#if CLKBY7 > 6553500

#define DIVISOR 2

#else

#define DIVISOR 1

#endif

/*

 * This is the counter value

 */

#define COUNT   ((CLKBY7 + (DIVISOR * HZ / 2)) / (DIVISOR * HZ))

extern unsigned long (*gettimeoffset)(void);

static unsigned long divisor;

/*

 * Get the time offset from the system PIT.  Note that if we have missed an

 * interrupt, then the PIT counter will roll over (ie, be negative).

 * This actually works out to be convenient.

 */

static unsigned long ebsa110_gettimeoffset(void)

{

        unsigned long offset, count;

        __raw_writeb(0x40, PIT_CTRL);

        count = __raw_readb(PIT_T1);

        count |= __raw_readb(PIT_T1) << 8;

        /*

         * If count > COUNT, make the number negative.

         */

        if (count > COUNT)

                count |= 0xffff0000;

        offset = COUNT * (DIVISOR - divisor);

        offset -= count;

        /*

         * `offset' is in units of timer counts.  Convert

         * offset to units of microseconds.

         */

        offset = offset * (1000000 / HZ) / (COUNT * DIVISOR);

        return offset;

}

int ebsa110_reset_timer(void)

{

        u32 count;

        /* latch and read timer 1 */

        __raw_writeb(0x40, PIT_CTRL);

        count = __raw_readb(PIT_T1);

        count |= __raw_readb(PIT_T1) << 8;

        count += COUNT;

        __raw_writeb(count & 0xff, PIT_T1);

        __raw_writeb(count >> 8, PIT_T1);

        if (divisor == 0)

                divisor = DIVISOR;

        divisor -= 1;

        return divisor;

}

void __init ebsa110_setup_timer(void)

{

        /*

         * Timer 1, mode 2, LSB/MSB

         */

        __raw_writeb(0x70, PIT_CTRL);

        __raw_writeb(COUNT & 0xff, PIT_T1);

        __raw_writeb(COUNT >> 8, PIT_T1);

        divisor = DIVISOR - 1;

        gettimeoffset = ebsa110_gettimeoffset;

}