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1da1180c PM |
1 | /* |
2 | * The idle loop for all SuperH platforms. | |
3 | * | |
2e046b94 | 4 | * Copyright (C) 2002 - 2009 Paul Mundt |
1da1180c PM |
5 | * |
6 | * This file is subject to the terms and conditions of the GNU General Public | |
7 | * License. See the file "COPYING" in the main directory of this archive | |
8 | * for more details. | |
9 | */ | |
10 | #include <linux/module.h> | |
11 | #include <linux/init.h> | |
12 | #include <linux/mm.h> | |
13 | #include <linux/pm.h> | |
14 | #include <linux/tick.h> | |
15 | #include <linux/preempt.h> | |
16 | #include <linux/thread_info.h> | |
17 | #include <linux/irqflags.h> | |
2e046b94 | 18 | #include <linux/smp.h> |
1da1180c PM |
19 | #include <asm/pgalloc.h> |
20 | #include <asm/system.h> | |
21 | #include <asm/atomic.h> | |
22 | ||
f533c3d3 | 23 | void (*pm_idle)(void) = NULL; |
fbb82b03 PM |
24 | |
25 | static int hlt_counter; | |
1da1180c PM |
26 | |
27 | static int __init nohlt_setup(char *__unused) | |
28 | { | |
29 | hlt_counter = 1; | |
30 | return 1; | |
31 | } | |
32 | __setup("nohlt", nohlt_setup); | |
33 | ||
34 | static int __init hlt_setup(char *__unused) | |
35 | { | |
36 | hlt_counter = 0; | |
37 | return 1; | |
38 | } | |
39 | __setup("hlt", hlt_setup); | |
40 | ||
f533c3d3 PM |
41 | static inline int hlt_works(void) |
42 | { | |
43 | return !hlt_counter; | |
44 | } | |
45 | ||
46 | /* | |
47 | * On SMP it's slightly faster (but much more power-consuming!) | |
48 | * to poll the ->work.need_resched flag instead of waiting for the | |
49 | * cross-CPU IPI to arrive. Use this option with caution. | |
50 | */ | |
51 | static void poll_idle(void) | |
52 | { | |
53 | local_irq_enable(); | |
54 | while (!need_resched()) | |
55 | cpu_relax(); | |
56 | } | |
57 | ||
e869a90e | 58 | void default_idle(void) |
1da1180c | 59 | { |
f533c3d3 | 60 | if (hlt_works()) { |
1da1180c PM |
61 | clear_thread_flag(TIF_POLLING_NRFLAG); |
62 | smp_mb__after_clear_bit(); | |
1da1180c | 63 | |
73a38b83 | 64 | set_bl_bit(); |
f533c3d3 PM |
65 | if (!need_resched()) { |
66 | local_irq_enable(); | |
1da1180c | 67 | cpu_sleep(); |
9dbe00a5 PM |
68 | } else |
69 | local_irq_enable(); | |
1da1180c | 70 | |
1da1180c | 71 | set_thread_flag(TIF_POLLING_NRFLAG); |
73a38b83 | 72 | clear_bl_bit(); |
1da1180c | 73 | } else |
f533c3d3 | 74 | poll_idle(); |
1da1180c PM |
75 | } |
76 | ||
f533c3d3 PM |
77 | /* |
78 | * The idle thread. There's no useful work to be done, so just try to conserve | |
79 | * power and have a low exit latency (ie sit in a loop waiting for somebody to | |
80 | * say that they'd like to reschedule) | |
81 | */ | |
1da1180c PM |
82 | void cpu_idle(void) |
83 | { | |
f533c3d3 PM |
84 | unsigned int cpu = smp_processor_id(); |
85 | ||
1da1180c PM |
86 | set_thread_flag(TIF_POLLING_NRFLAG); |
87 | ||
88 | /* endless idle loop with no priority at all */ | |
89 | while (1) { | |
f533c3d3 | 90 | tick_nohz_stop_sched_tick(1); |
1da1180c | 91 | |
f533c3d3 | 92 | while (!need_resched() && cpu_online(cpu)) { |
0e6d4986 PM |
93 | check_pgt_cache(); |
94 | rmb(); | |
95 | ||
f533c3d3 PM |
96 | local_irq_disable(); |
97 | /* Don't trace irqs off for idle */ | |
98 | stop_critical_timings(); | |
99 | pm_idle(); | |
100 | /* | |
101 | * Sanity check to ensure that pm_idle() returns | |
102 | * with IRQs enabled | |
103 | */ | |
104 | WARN_ON(irqs_disabled()); | |
105 | start_critical_timings(); | |
106 | } | |
1da1180c | 107 | |
1da1180c | 108 | tick_nohz_restart_sched_tick(); |
1da1180c PM |
109 | preempt_enable_no_resched(); |
110 | schedule(); | |
111 | preempt_disable(); | |
1da1180c PM |
112 | } |
113 | } | |
2e046b94 | 114 | |
90851c40 | 115 | void __init select_idle_routine(void) |
f533c3d3 PM |
116 | { |
117 | /* | |
118 | * If a platform has set its own idle routine, leave it alone. | |
119 | */ | |
120 | if (pm_idle) | |
121 | return; | |
122 | ||
123 | if (hlt_works()) | |
124 | pm_idle = default_idle; | |
125 | else | |
126 | pm_idle = poll_idle; | |
127 | } | |
128 | ||
2e046b94 PM |
129 | static void do_nothing(void *unused) |
130 | { | |
131 | } | |
132 | ||
fbb82b03 PM |
133 | void stop_this_cpu(void *unused) |
134 | { | |
135 | local_irq_disable(); | |
136 | cpu_clear(smp_processor_id(), cpu_online_map); | |
137 | ||
138 | for (;;) | |
139 | cpu_sleep(); | |
140 | } | |
141 | ||
2e046b94 PM |
142 | /* |
143 | * cpu_idle_wait - Used to ensure that all the CPUs discard old value of | |
144 | * pm_idle and update to new pm_idle value. Required while changing pm_idle | |
145 | * handler on SMP systems. | |
146 | * | |
147 | * Caller must have changed pm_idle to the new value before the call. Old | |
148 | * pm_idle value will not be used by any CPU after the return of this function. | |
149 | */ | |
150 | void cpu_idle_wait(void) | |
151 | { | |
152 | smp_mb(); | |
153 | /* kick all the CPUs so that they exit out of pm_idle */ | |
154 | smp_call_function(do_nothing, NULL, 1); | |
155 | } | |
156 | EXPORT_SYMBOL_GPL(cpu_idle_wait); |