LXR linux/arch/mips/kernel/csrc-ioasic.c

   1/*
   2 *  DEC I/O ASIC's counter clocksource
   3 *
   4 *  Copyright (C) 2008  Yoichi Yuasa <yuasa@linux-mips.org>
   5 *
   6 *  This program is free software; you can redistribute it and/or modify
   7 *  it under the terms of the GNU General Public License as published by
   8 *  the Free Software Foundation; either version 2 of the License, or
   9 *  (at your option) any later version.
  10 *
  11 *  This program is distributed in the hope that it will be useful,
  12 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 *  GNU General Public License for more details.
  15 */
  16#include <linux/clocksource.h>
  17#include <linux/sched_clock.h>
  18#include <linux/init.h>
  19
  20#include <asm/ds1287.h>
  21#include <asm/time.h>
  22#include <asm/dec/ioasic.h>
  23#include <asm/dec/ioasic_addrs.h>
  24
  25static u64 dec_ioasic_hpt_read(struct clocksource *cs)
  26{
  27        return ioasic_read(IO_REG_FCTR);
  28}
  29
  30static struct clocksource clocksource_dec = {
  31        .name           = "dec-ioasic",
  32        .read           = dec_ioasic_hpt_read,
  33        .mask           = CLOCKSOURCE_MASK(32),
  34        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  35};
  36
  37static u64 notrace dec_ioasic_read_sched_clock(void)
  38{
  39        return ioasic_read(IO_REG_FCTR);
  40}
  41
  42int __init dec_ioasic_clocksource_init(void)
  43{
  44        unsigned int freq;
  45        u32 start, end;
  46        int i = HZ / 8;
  47
  48        ds1287_timer_state();
  49        while (!ds1287_timer_state())
  50                ;
  51
  52        start = dec_ioasic_hpt_read(&clocksource_dec);
  53
  54        while (i--)
  55                while (!ds1287_timer_state())
  56                        ;
  57
  58        end = dec_ioasic_hpt_read(&clocksource_dec);
  59
  60        freq = (end - start) * 8;
  61
  62        /* An early revision of the I/O ASIC didn't have the counter.  */
  63        if (!freq)
  64                return -ENXIO;
  65
  66        printk(KERN_INFO "I/O ASIC clock frequency %dHz\n", freq);
  67
  68        clocksource_dec.rating = 200 + freq / 10000000;
  69        clocksource_register_hz(&clocksource_dec, freq);
  70
  71        sched_clock_register(dec_ioasic_read_sched_clock, 32, freq);
  72
  73        return 0;
  74}
  75