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 *  You should have received a copy of the GNU General Public License
  17 *  along with this program; if not, write to the Free Software
  18 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19 */
  20#include <linux/clocksource.h>
  21#include <linux/init.h>
  22
  23#include <asm/ds1287.h>
  24#include <asm/time.h>
  25#include <asm/dec/ioasic.h>
  26#include <asm/dec/ioasic_addrs.h>
  27
  28static cycle_t dec_ioasic_hpt_read(struct clocksource *cs)
  29{
  30        return ioasic_read(IO_REG_FCTR);
  31}
  32
  33static struct clocksource clocksource_dec = {
  34        .name           = "dec-ioasic",
  35        .read           = dec_ioasic_hpt_read,
  36        .mask           = CLOCKSOURCE_MASK(32),
  37        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  38};
  39
  40void __init dec_ioasic_clocksource_init(void)
  41{
  42        unsigned int freq;
  43        u32 start, end;
  44        int i = HZ / 10;
  45
  46
  47        while (!ds1287_timer_state())
  48                ;
  49
  50        start = dec_ioasic_hpt_read(&clocksource_dec);
  51
  52        while (i--)
  53                while (!ds1287_timer_state())
  54                        ;
  55
  56        end = dec_ioasic_hpt_read(&clocksource_dec);
  57
  58        freq = (end - start) * 10;
  59        printk(KERN_INFO "I/O ASIC clock frequency %dHz\n", freq);
  60
  61        clocksource_dec.rating = 200 + freq / 10000000;
  62        clocksource_register_hz(&clocksource_dec, freq);
  63}
  64