arch/mips/kernel/csrc-ioasic.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *  DEC I/O ASIC's counter clocksource
   4  *
   5  *  Copyright (C) 2008  Yoichi Yuasa <yuasa@linux-mips.org>
   6  */
   7 #include <linux/clocksource.h>
   8 #include <linux/sched_clock.h>
   9 #include <linux/init.h>
  10
  11 #include <asm/ds1287.h>
  12 #include <asm/time.h>
  13 #include <asm/dec/ioasic.h>
  14 #include <asm/dec/ioasic_addrs.h>
  15
  16 static u64 dec_ioasic_hpt_read(struct clocksource *cs)
  17 {
  18         return ioasic_read(IO_REG_FCTR);
  19 }
  20
  21 static struct clocksource clocksource_dec = {
  22         .name           = "dec-ioasic",
  23         .read           = dec_ioasic_hpt_read,
  24         .mask           = CLOCKSOURCE_MASK(32),
  25         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  26 };
  27
  28 static u64 notrace dec_ioasic_read_sched_clock(void)
  29 {
  30         return ioasic_read(IO_REG_FCTR);
  31 }
  32
  33 int __init dec_ioasic_clocksource_init(void)
  34 {
  35         unsigned int freq;
  36         u32 start, end;
  37         int i = HZ / 8;
  38
  39         ds1287_timer_state();
  40         while (!ds1287_timer_state())
  41                 ;
  42
  43         start = dec_ioasic_hpt_read(&clocksource_dec);
  44
  45         while (i--)
  46                 while (!ds1287_timer_state())
  47                         ;
  48
  49         end = dec_ioasic_hpt_read(&clocksource_dec);
  50
  51         freq = (end - start) * 8;
  52
  53         /* An early revision of the I/O ASIC didn't have the counter.  */
  54         if (!freq)
  55                 return -ENXIO;
  56
  57         printk(KERN_INFO "I/O ASIC clock frequency %dHz\n", freq);
  58
  59         clocksource_dec.rating = 200 + freq / 10000000;
  60         clocksource_register_hz(&clocksource_dec, freq);
  61
  62         sched_clock_register(dec_ioasic_read_sched_clock, 32, freq);
  63
  64         return 0;
  65 }