1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright 2001 MontaVista Software Inc.
4 * Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
5 * Copyright (c) 2003, 2004 Maciej W. Rozycki
6 *
7 * Common time service routines for MIPS machines.
8 */
9 #include <linux/bug.h>
10 #include <linux/clockchips.h>
11 #include <linux/types.h>
12 #include <linux/kernel.h>
13 #include <linux/init.h>
14 #include <linux/sched.h>
15 #include <linux/param.h>
16 #include <linux/time.h>
17 #include <linux/timex.h>
18 #include <linux/smp.h>
19 #include <linux/spinlock.h>
20 #include <linux/export.h>
21
22 #include <asm/cpu-features.h>
23 #include <asm/cpu-type.h>
24 #include <asm/div64.h>
25 #include <asm/time.h>
26
27 /*
28 * forward reference
29 */
30 DEFINE_SPINLOCK(rtc_lock);
31 EXPORT_SYMBOL(rtc_lock);
32
33 static int null_perf_irq(void)
34 {
35 return 0;
36 }
37
38 int (*perf_irq)(void) = null_perf_irq;
39
40 EXPORT_SYMBOL(perf_irq);
41
42 /*
43 * time_init() - it does the following things.
44 *
45 * 1) plat_time_init() -
46 * a) (optional) set up RTC routines,
47 * b) (optional) calibrate and set the mips_hpt_frequency
48 * (only needed if you intended to use cpu counter as timer interrupt
49 * source)
50 * 2) calculate a couple of cached variables for later usage
51 */
52
53 unsigned int mips_hpt_frequency;
54 EXPORT_SYMBOL_GPL(mips_hpt_frequency);
55
56 static __init int cpu_has_mfc0_count_bug(void)
57 {
58 switch (current_cpu_type()) {
59 case CPU_R4000PC:
60 case CPU_R4000SC:
61 case CPU_R4000MC:
62 /*
63 * V3.0 is documented as suffering from the mfc0 from count bug.
64 * Afaik this is the last version of the R4000. Later versions
65 * were marketed as R4400.
66 */
67 return 1;
68
69 case CPU_R4400PC:
70 case CPU_R4400SC:
71 case CPU_R4400MC:
72 /*
73 * The published errata for the R4400 up to 3.0 say the CPU
74 * has the mfc0 from count bug.
75 */
76 if ((current_cpu_data.processor_id & 0xff) <= 0x30)
77 return 1;
78
79 /*
80 * we assume newer revisions are ok
81 */
82 return 0;
83 }
84
85 return 0;
86 }
87
88 void __init time_init(void)
89 {
90 plat_time_init();
91
92 /*
93 * The use of the R4k timer as a clock event takes precedence;
94 * if reading the Count register might interfere with the timer
95 * interrupt, then we don't use the timer as a clock source.
96 * We may still use the timer as a clock source though if the
97 * timer interrupt isn't reliable; the interference doesn't
98 * matter then, because we don't use the interrupt.
99 */
100 if (mips_clockevent_init() != 0 || !cpu_has_mfc0_count_bug())
101 init_mips_clocksource();
102 }