csrc-ioasic.c

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/*
 *  DEC I/O ASIC's counter clocksource
 *
 *  Copyright (C) 2008  Yoichi Yuasa <[email protected]>
 *
 *  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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
#include <linux/clocksource.h>
#include <linux/init.h>

#include <asm/ds1287.h>
#include <asm/time.h>
#include <asm/dec/ioasic.h>
#include <asm/dec/ioasic_addrs.h>

static cycle_t dec_ioasic_hpt_read(struct clocksource *cs)
{
    return ioasic_read(IO_REG_FCTR);
}

static struct clocksource clocksource_dec = {
    .name       = "dec-ioasic",
    .read       = dec_ioasic_hpt_read,
    .mask       = CLOCKSOURCE_MASK(32),
    .flags      = CLOCK_SOURCE_IS_CONTINUOUS,
};

void __init dec_ioasic_clocksource_init(void)
{
    unsigned int freq;
    u32 start, end;
    int i = HZ / 10;


    while (!ds1287_timer_state())
        ;

    start = dec_ioasic_hpt_read(&clocksource_dec);

    while (i--)
        while (!ds1287_timer_state())
            ;

    end = dec_ioasic_hpt_read(&clocksource_dec);

    freq = (end - start) * 10;
    printk(KERN_INFO "I/O ASIC clock frequency %dHz\n", freq);

    clocksource_dec.rating = 200 + freq / 10000000;
    clocksource_register_hz(&clocksource_dec, freq);
}