arch/mips/rb532/time.c

   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  */
  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
  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 }