1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Carsten Langgaard, carstenl@mips.com
4  * Copyright (C) 1999,2000 MIPS Technologies, Inc.  All rights reserved.
5  *
6  *  Setting up the clock on the MIPS boards.
7  */
8 
9 #include <linux/init.h>
10 #include <linux/kernel_stat.h>
11 #include <linux/ptrace.h>
12 #include <linux/sched.h>
13 #include <linux/spinlock.h>
14 #include <linux/mc146818rtc.h>
15 #include <linux/irq.h>
16 #include <linux/timex.h>
17 
18 #include <asm/mipsregs.h>
19 #include <asm/time.h>
20 #include <asm/mach-rc32434/rc32434.h>
21 
22 extern unsigned int idt_cpu_freq;
23 
24 /*
25  * Figure out the r4k offset, the amount to increment the compare
26  * register for each time tick. There is no RTC available.
27  *
28  * The RC32434 counts at half the CPU *core* speed.
29  */
cal_r4koff(void)30 static unsigned long __init cal_r4koff(void)
31 {
32 	mips_hpt_frequency = idt_cpu_freq * IDT_CLOCK_MULT / 2;
33 
34 	return mips_hpt_frequency / HZ;
35 }
36 
plat_time_init(void)37 void __init plat_time_init(void)
38 {
39 	unsigned int est_freq;
40 	unsigned long flags, r4k_offset;
41 
42 	local_irq_save(flags);
43 
44 	printk(KERN_INFO "calculating r4koff... ");
45 	r4k_offset = cal_r4koff();
46 	printk("%08lx(%d)\n", r4k_offset, (int) r4k_offset);
47 
48 	est_freq = 2 * r4k_offset * HZ;
49 	est_freq += 5000;	/* round */
50 	est_freq -= est_freq % 10000;
51 	printk(KERN_INFO "CPU frequency %d.%02d MHz\n", est_freq / 1000000,
52 	       (est_freq % 1000000) * 100 / 1000000);
53 	local_irq_restore(flags);
54 }
55