Commit | Line | Data |
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112f38a4 RK |
1 | /* |
2 | * sched_clock.c: support for extending counters to full 64-bit ns counter | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License version 2 as | |
6 | * published by the Free Software Foundation. | |
7 | */ | |
8 | #include <linux/clocksource.h> | |
9 | #include <linux/init.h> | |
10 | #include <linux/jiffies.h> | |
11 | #include <linux/kernel.h> | |
a42c3629 | 12 | #include <linux/moduleparam.h> |
112f38a4 | 13 | #include <linux/sched.h> |
f153d017 | 14 | #include <linux/syscore_ops.h> |
112f38a4 RK |
15 | #include <linux/timer.h> |
16 | ||
17 | #include <asm/sched_clock.h> | |
18 | ||
2f0778af MZ |
19 | struct clock_data { |
20 | u64 epoch_ns; | |
21 | u32 epoch_cyc; | |
22 | u32 epoch_cyc_copy; | |
c115739d | 23 | unsigned long rate; |
2f0778af MZ |
24 | u32 mult; |
25 | u32 shift; | |
237ec6f2 | 26 | bool suspended; |
2f0778af MZ |
27 | }; |
28 | ||
112f38a4 RK |
29 | static void sched_clock_poll(unsigned long wrap_ticks); |
30 | static DEFINE_TIMER(sched_clock_timer, sched_clock_poll, 0, 0); | |
a42c3629 RK |
31 | static int irqtime = -1; |
32 | ||
33 | core_param(irqtime, irqtime, int, 0400); | |
2f0778af MZ |
34 | |
35 | static struct clock_data cd = { | |
36 | .mult = NSEC_PER_SEC / HZ, | |
37 | }; | |
38 | ||
39 | static u32 __read_mostly sched_clock_mask = 0xffffffff; | |
40 | ||
41 | static u32 notrace jiffy_sched_clock_read(void) | |
42 | { | |
43 | return (u32)(jiffies - INITIAL_JIFFIES); | |
44 | } | |
45 | ||
46 | static u32 __read_mostly (*read_sched_clock)(void) = jiffy_sched_clock_read; | |
47 | ||
cea15092 | 48 | static inline u64 notrace cyc_to_ns(u64 cyc, u32 mult, u32 shift) |
2f0778af MZ |
49 | { |
50 | return (cyc * mult) >> shift; | |
51 | } | |
52 | ||
cea15092 | 53 | static unsigned long long notrace cyc_to_sched_clock(u32 cyc, u32 mask) |
2f0778af MZ |
54 | { |
55 | u64 epoch_ns; | |
56 | u32 epoch_cyc; | |
57 | ||
58 | /* | |
59 | * Load the epoch_cyc and epoch_ns atomically. We do this by | |
60 | * ensuring that we always write epoch_cyc, epoch_ns and | |
61 | * epoch_cyc_copy in strict order, and read them in strict order. | |
62 | * If epoch_cyc and epoch_cyc_copy are not equal, then we're in | |
63 | * the middle of an update, and we should repeat the load. | |
64 | */ | |
65 | do { | |
66 | epoch_cyc = cd.epoch_cyc; | |
67 | smp_rmb(); | |
68 | epoch_ns = cd.epoch_ns; | |
69 | smp_rmb(); | |
70 | } while (epoch_cyc != cd.epoch_cyc_copy); | |
71 | ||
72 | return epoch_ns + cyc_to_ns((cyc - epoch_cyc) & mask, cd.mult, cd.shift); | |
73 | } | |
74 | ||
75 | /* | |
76 | * Atomically update the sched_clock epoch. | |
77 | */ | |
78 | static void notrace update_sched_clock(void) | |
79 | { | |
80 | unsigned long flags; | |
81 | u32 cyc; | |
82 | u64 ns; | |
83 | ||
84 | cyc = read_sched_clock(); | |
85 | ns = cd.epoch_ns + | |
86 | cyc_to_ns((cyc - cd.epoch_cyc) & sched_clock_mask, | |
87 | cd.mult, cd.shift); | |
88 | /* | |
89 | * Write epoch_cyc and epoch_ns in a way that the update is | |
90 | * detectable in cyc_to_fixed_sched_clock(). | |
91 | */ | |
92 | raw_local_irq_save(flags); | |
7c4e9ced | 93 | cd.epoch_cyc_copy = cyc; |
2f0778af MZ |
94 | smp_wmb(); |
95 | cd.epoch_ns = ns; | |
96 | smp_wmb(); | |
7c4e9ced | 97 | cd.epoch_cyc = cyc; |
2f0778af MZ |
98 | raw_local_irq_restore(flags); |
99 | } | |
112f38a4 RK |
100 | |
101 | static void sched_clock_poll(unsigned long wrap_ticks) | |
102 | { | |
103 | mod_timer(&sched_clock_timer, round_jiffies(jiffies + wrap_ticks)); | |
2f0778af | 104 | update_sched_clock(); |
112f38a4 RK |
105 | } |
106 | ||
2f0778af | 107 | void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate) |
112f38a4 RK |
108 | { |
109 | unsigned long r, w; | |
110 | u64 res, wrap; | |
111 | char r_unit; | |
112 | ||
c115739d RH |
113 | if (cd.rate > rate) |
114 | return; | |
115 | ||
2f0778af MZ |
116 | BUG_ON(bits > 32); |
117 | WARN_ON(!irqs_disabled()); | |
2f0778af MZ |
118 | read_sched_clock = read; |
119 | sched_clock_mask = (1 << bits) - 1; | |
c115739d | 120 | cd.rate = rate; |
112f38a4 RK |
121 | |
122 | /* calculate the mult/shift to convert counter ticks to ns. */ | |
2f0778af | 123 | clocks_calc_mult_shift(&cd.mult, &cd.shift, rate, NSEC_PER_SEC, 0); |
112f38a4 RK |
124 | |
125 | r = rate; | |
126 | if (r >= 4000000) { | |
127 | r /= 1000000; | |
128 | r_unit = 'M'; | |
2f0778af | 129 | } else if (r >= 1000) { |
112f38a4 RK |
130 | r /= 1000; |
131 | r_unit = 'k'; | |
2f0778af MZ |
132 | } else |
133 | r_unit = ' '; | |
112f38a4 RK |
134 | |
135 | /* calculate how many ns until we wrap */ | |
2f0778af | 136 | wrap = cyc_to_ns((1ULL << bits) - 1, cd.mult, cd.shift); |
112f38a4 RK |
137 | do_div(wrap, NSEC_PER_MSEC); |
138 | w = wrap; | |
139 | ||
140 | /* calculate the ns resolution of this counter */ | |
2f0778af | 141 | res = cyc_to_ns(1ULL, cd.mult, cd.shift); |
112f38a4 | 142 | pr_info("sched_clock: %u bits at %lu%cHz, resolution %lluns, wraps every %lums\n", |
2f0778af | 143 | bits, r, r_unit, res, w); |
112f38a4 RK |
144 | |
145 | /* | |
146 | * Start the timer to keep sched_clock() properly updated and | |
147 | * sets the initial epoch. | |
148 | */ | |
149 | sched_clock_timer.data = msecs_to_jiffies(w - (w / 10)); | |
2f0778af | 150 | update_sched_clock(); |
112f38a4 RK |
151 | |
152 | /* | |
153 | * Ensure that sched_clock() starts off at 0ns | |
154 | */ | |
2f0778af MZ |
155 | cd.epoch_ns = 0; |
156 | ||
a42c3629 RK |
157 | /* Enable IRQ time accounting if we have a fast enough sched_clock */ |
158 | if (irqtime > 0 || (irqtime == -1 && rate >= 1000000)) | |
159 | enable_sched_clock_irqtime(); | |
160 | ||
2f0778af MZ |
161 | pr_debug("Registered %pF as sched_clock source\n", read); |
162 | } | |
163 | ||
7e48c0b9 | 164 | static unsigned long long notrace sched_clock_32(void) |
2f0778af MZ |
165 | { |
166 | u32 cyc = read_sched_clock(); | |
167 | return cyc_to_sched_clock(cyc, sched_clock_mask); | |
112f38a4 | 168 | } |
211baa70 | 169 | |
7e48c0b9 RH |
170 | unsigned long long __read_mostly (*sched_clock_func)(void) = sched_clock_32; |
171 | ||
172 | unsigned long long notrace sched_clock(void) | |
173 | { | |
ffbfb5e3 SB |
174 | if (cd.suspended) |
175 | return cd.epoch_ns; | |
176 | ||
7e48c0b9 RH |
177 | return sched_clock_func(); |
178 | } | |
179 | ||
211baa70 RK |
180 | void __init sched_clock_postinit(void) |
181 | { | |
2f0778af MZ |
182 | /* |
183 | * If no sched_clock function has been provided at that point, | |
184 | * make it the final one one. | |
185 | */ | |
186 | if (read_sched_clock == jiffy_sched_clock_read) | |
187 | setup_sched_clock(jiffy_sched_clock_read, 32, HZ); | |
188 | ||
211baa70 RK |
189 | sched_clock_poll(sched_clock_timer.data); |
190 | } | |
f153d017 RK |
191 | |
192 | static int sched_clock_suspend(void) | |
193 | { | |
194 | sched_clock_poll(sched_clock_timer.data); | |
6a4dae5e | 195 | cd.suspended = true; |
f153d017 RK |
196 | return 0; |
197 | } | |
198 | ||
237ec6f2 CC |
199 | static void sched_clock_resume(void) |
200 | { | |
6a4dae5e FB |
201 | cd.epoch_cyc = read_sched_clock(); |
202 | cd.epoch_cyc_copy = cd.epoch_cyc; | |
203 | cd.suspended = false; | |
237ec6f2 CC |
204 | } |
205 | ||
f153d017 RK |
206 | static struct syscore_ops sched_clock_ops = { |
207 | .suspend = sched_clock_suspend, | |
237ec6f2 | 208 | .resume = sched_clock_resume, |
f153d017 RK |
209 | }; |
210 | ||
211 | static int __init sched_clock_syscore_init(void) | |
212 | { | |
213 | register_syscore_ops(&sched_clock_ops); | |
214 | return 0; | |
215 | } | |
216 | device_initcall(sched_clock_syscore_init); |