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
  28 static cycle_t dec_ioasic_hpt_read(struct clocksource *cs)
  29 {
  30         return ioasic_read(IO_REG_FCTR);
  31 }
  32
  33 static 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
  40 int __init dec_ioasic_clocksource_init(void)
  41 {
  42         unsigned int freq;
  43         u32 start, end;
  44         int i = HZ / 8;
  45
  46         ds1287_timer_state();
  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) * 8;
  59
  60         /* An early revision of the I/O ASIC didn't have the counter.  */
  61         if (!freq)
  62                 return -ENXIO;
  63
  64         printk(KERN_INFO "I/O ASIC clock frequency %dHz\n", freq);
  65
  66         clocksource_dec.rating = 200 + freq / 10000000;
  67         clocksource_register_hz(&clocksource_dec, freq);
  68         return 0;
  69 }