release/src-rt-6.x.4708/linux/linux-2.6.36/arch/mips/rb532/time.c

   1 /*
   2  * Carsten Langgaard, carstenl@mips.com
   3  * Copyright (C) 1999,2000 MIPS Technologies, Inc.  All rights reserved.
   4  *
   5  *  This program is free software; you can distribute it and/or modify it
   6  *  under the terms of the GNU General Public License (Version 2) as
   7  *  published by the Free Software Foundation.
   8  *
   9  *  This program is distributed in the hope it will be useful, but WITHOUT
  10  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  *  for more details.
  13  *
  14  *  You should have received a copy of the GNU General Public License along
  15  *  with this program; if not, write to the Free Software Foundation, Inc.,
  16  *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
  17  *
  18  *  Setting up the clock on the MIPS boards.
  19  */
  20
  21 #include <linux/init.h>
  22 #include <linux/kernel_stat.h>
  23 #include <linux/ptrace.h>
  24 #include <linux/sched.h>
  25 #include <linux/spinlock.h>
  26 #include <linux/mc146818rtc.h>
  27 #include <linux/irq.h>
  28 #include <linux/timex.h>
  29
  30 #include <asm/mipsregs.h>
  31 #include <asm/time.h>
  32 #include <asm/mach-rc32434/rc32434.h>
  33
  34 extern unsigned int idt_cpu_freq;
  35
  36 /*
  37  * Figure out the r4k offset, the amount to increment the compare
  38  * register for each time tick. There is no RTC available.
  39  *
  40  * The RC32434 counts at half the CPU *core* speed.
  41  */
  42 static unsigned long __init cal_r4koff(void)
  43 {
  44         mips_hpt_frequency = idt_cpu_freq * IDT_CLOCK_MULT / 2;
  45
  46         return mips_hpt_frequency / HZ;
  47 }
  48
  49 void __init plat_time_init(void)
  50 {
  51         unsigned int est_freq;
  52         unsigned long flags, r4k_offset;
  53
  54         local_irq_save(flags);
  55
  56         printk(KERN_INFO "calculating r4koff... ");
  57         r4k_offset = cal_r4koff();
  58         printk("%08lx(%d)\n", r4k_offset, (int) r4k_offset);
  59
  60         est_freq = 2 * r4k_offset * HZ;
  61         est_freq += 5000;       /* round */
  62         est_freq -= est_freq % 10000;
  63         printk(KERN_INFO "CPU frequency %d.%02d MHz\n", est_freq / 1000000,
  64                (est_freq % 1000000) * 100 / 1000000);
  65         local_irq_restore(flags);
  66 }