xref: /openbmc/linux/arch/mips/kernel/csrc-ioasic.c (revision c942fddf)
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 
dec_ioasic_hpt_read(struct clocksource * cs)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 
dec_ioasic_read_sched_clock(void)28 static u64 notrace dec_ioasic_read_sched_clock(void)
29 {
30 	return ioasic_read(IO_REG_FCTR);
31 }
32 
dec_ioasic_clocksource_init(void)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