Linux Kernel  3.7.1
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time.c
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1 /*
2  * Carsten Langgaard, [email protected]
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>
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 {
45 
46  return mips_hpt_frequency / HZ;
47 }
48 
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 }