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 }
66
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