LXR linux/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
  16static u64 dec_ioasic_hpt_read(struct clocksource *cs)
  17{
  18        return ioasic_read(IO_REG_FCTR);
  19}
  20
  21static 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
  28static u64 notrace dec_ioasic_read_sched_clock(void)
  29{
  30        return ioasic_read(IO_REG_FCTR);
  31}
  32
  33int __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}
  66