xref: /openbmc/linux/arch/mips/kernel/time.c (revision f9a1dbc8)
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 #include <linux/cpufreq.h>
22 #include <linux/delay.h>
23 
24 #include <asm/cpu-features.h>
25 #include <asm/cpu-type.h>
26 #include <asm/div64.h>
27 #include <asm/time.h>
28 
29 #ifdef CONFIG_CPU_FREQ
30 
31 static DEFINE_PER_CPU(unsigned long, pcp_lpj_ref);
32 static DEFINE_PER_CPU(unsigned long, pcp_lpj_ref_freq);
33 static unsigned long glb_lpj_ref;
34 static unsigned long glb_lpj_ref_freq;
35 
cpufreq_callback(struct notifier_block * nb,unsigned long val,void * data)36 static int cpufreq_callback(struct notifier_block *nb,
37 			    unsigned long val, void *data)
38 {
39 	struct cpufreq_freqs *freq = data;
40 	struct cpumask *cpus = freq->policy->cpus;
41 	unsigned long lpj;
42 	int cpu;
43 
44 	/*
45 	 * Skip lpj numbers adjustment if the CPU-freq transition is safe for
46 	 * the loops delay. (Is this possible?)
47 	 */
48 	if (freq->flags & CPUFREQ_CONST_LOOPS)
49 		return NOTIFY_OK;
50 
51 	/* Save the initial values of the lpjes for future scaling. */
52 	if (!glb_lpj_ref) {
53 		glb_lpj_ref = boot_cpu_data.udelay_val;
54 		glb_lpj_ref_freq = freq->old;
55 
56 		for_each_online_cpu(cpu) {
57 			per_cpu(pcp_lpj_ref, cpu) =
58 				cpu_data[cpu].udelay_val;
59 			per_cpu(pcp_lpj_ref_freq, cpu) = freq->old;
60 		}
61 	}
62 
63 	/*
64 	 * Adjust global lpj variable and per-CPU udelay_val number in
65 	 * accordance with the new CPU frequency.
66 	 */
67 	if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
68 	    (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
69 		loops_per_jiffy = cpufreq_scale(glb_lpj_ref,
70 						glb_lpj_ref_freq,
71 						freq->new);
72 
73 		for_each_cpu(cpu, cpus) {
74 			lpj = cpufreq_scale(per_cpu(pcp_lpj_ref, cpu),
75 					    per_cpu(pcp_lpj_ref_freq, cpu),
76 					    freq->new);
77 			cpu_data[cpu].udelay_val = (unsigned int)lpj;
78 		}
79 	}
80 
81 	return NOTIFY_OK;
82 }
83 
84 static struct notifier_block cpufreq_notifier = {
85 	.notifier_call  = cpufreq_callback,
86 };
87 
register_cpufreq_notifier(void)88 static int __init register_cpufreq_notifier(void)
89 {
90 	return cpufreq_register_notifier(&cpufreq_notifier,
91 					 CPUFREQ_TRANSITION_NOTIFIER);
92 }
93 core_initcall(register_cpufreq_notifier);
94 
95 #endif /* CONFIG_CPU_FREQ */
96 
97 /*
98  * forward reference
99  */
100 DEFINE_SPINLOCK(rtc_lock);
101 EXPORT_SYMBOL(rtc_lock);
102 
null_perf_irq(void)103 static int null_perf_irq(void)
104 {
105 	return 0;
106 }
107 
108 int (*perf_irq)(void) = null_perf_irq;
109 
110 EXPORT_SYMBOL(perf_irq);
111 
112 /*
113  * time_init() - it does the following things.
114  *
115  * 1) plat_time_init() -
116  *	a) (optional) set up RTC routines,
117  *	b) (optional) calibrate and set the mips_hpt_frequency
118  *	    (only needed if you intended to use cpu counter as timer interrupt
119  *	     source)
120  * 2) calculate a couple of cached variables for later usage
121  */
122 
123 unsigned int mips_hpt_frequency;
124 EXPORT_SYMBOL_GPL(mips_hpt_frequency);
125 
cpu_has_mfc0_count_bug(void)126 static __init int cpu_has_mfc0_count_bug(void)
127 {
128 	switch (current_cpu_type()) {
129 	case CPU_R4000PC:
130 	case CPU_R4000SC:
131 	case CPU_R4000MC:
132 		/*
133 		 * V3.0 is documented as suffering from the mfc0 from count bug.
134 		 * Afaik this is the last version of the R4000.	 Later versions
135 		 * were marketed as R4400.
136 		 */
137 		return 1;
138 
139 	case CPU_R4400PC:
140 	case CPU_R4400SC:
141 	case CPU_R4400MC:
142 		/*
143 		 * The published errata for the R4400 up to 3.0 say the CPU
144 		 * has the mfc0 from count bug.  This seems the last version
145 		 * produced.
146 		 */
147 		return 1;
148 	}
149 
150 	return 0;
151 }
152 
time_init(void)153 void __init time_init(void)
154 {
155 	plat_time_init();
156 
157 	/*
158 	 * The use of the R4k timer as a clock event takes precedence;
159 	 * if reading the Count register might interfere with the timer
160 	 * interrupt, then we don't use the timer as a clock source.
161 	 * We may still use the timer as a clock source though if the
162 	 * timer interrupt isn't reliable; the interference doesn't
163 	 * matter then, because we don't use the interrupt.
164 	 */
165 	if (mips_clockevent_init() != 0 || !cpu_has_mfc0_count_bug())
166 		init_mips_clocksource();
167 }
168