1 /* 2 * Idle daemon for PowerPC. Idle daemon will handle any action 3 * that needs to be taken when the system becomes idle. 4 * 5 * Originally written by Cort Dougan (cort@cs.nmt.edu). 6 * Subsequent 32-bit hacking by Tom Rini, Armin Kuster, 7 * Paul Mackerras and others. 8 * 9 * iSeries supported added by Mike Corrigan <mikejc@us.ibm.com> 10 * 11 * Additional shared processor, SMT, and firmware support 12 * Copyright (c) 2003 Dave Engebretsen <engebret@us.ibm.com> 13 * 14 * 32-bit and 64-bit versions merged by Paul Mackerras <paulus@samba.org> 15 * 16 * This program is free software; you can redistribute it and/or 17 * modify it under the terms of the GNU General Public License 18 * as published by the Free Software Foundation; either version 19 * 2 of the License, or (at your option) any later version. 20 */ 21 22 #include <linux/sched.h> 23 #include <linux/kernel.h> 24 #include <linux/smp.h> 25 #include <linux/cpu.h> 26 #include <linux/sysctl.h> 27 #include <linux/tick.h> 28 29 #include <asm/system.h> 30 #include <asm/processor.h> 31 #include <asm/cputable.h> 32 #include <asm/time.h> 33 #include <asm/machdep.h> 34 #include <asm/smp.h> 35 36 #ifdef CONFIG_HOTPLUG_CPU 37 #define cpu_should_die() cpu_is_offline(smp_processor_id()) 38 #else 39 #define cpu_should_die() 0 40 #endif 41 42 unsigned long cpuidle_disable = IDLE_NO_OVERRIDE; 43 EXPORT_SYMBOL(cpuidle_disable); 44 45 static int __init powersave_off(char *arg) 46 { 47 ppc_md.power_save = NULL; 48 cpuidle_disable = IDLE_POWERSAVE_OFF; 49 return 0; 50 } 51 __setup("powersave=off", powersave_off); 52 53 /* 54 * The body of the idle task. 55 */ 56 void cpu_idle(void) 57 { 58 if (ppc_md.idle_loop) 59 ppc_md.idle_loop(); /* doesn't return */ 60 61 set_thread_flag(TIF_POLLING_NRFLAG); 62 while (1) { 63 tick_nohz_idle_enter(); 64 rcu_idle_enter(); 65 66 while (!need_resched() && !cpu_should_die()) { 67 ppc64_runlatch_off(); 68 69 if (ppc_md.power_save) { 70 clear_thread_flag(TIF_POLLING_NRFLAG); 71 /* 72 * smp_mb is so clearing of TIF_POLLING_NRFLAG 73 * is ordered w.r.t. need_resched() test. 74 */ 75 smp_mb(); 76 local_irq_disable(); 77 78 /* Don't trace irqs off for idle */ 79 stop_critical_timings(); 80 81 /* check again after disabling irqs */ 82 if (!need_resched() && !cpu_should_die()) 83 ppc_md.power_save(); 84 85 start_critical_timings(); 86 87 local_irq_enable(); 88 set_thread_flag(TIF_POLLING_NRFLAG); 89 90 } else { 91 /* 92 * Go into low thread priority and possibly 93 * low power mode. 94 */ 95 HMT_low(); 96 HMT_very_low(); 97 } 98 } 99 100 HMT_medium(); 101 ppc64_runlatch_on(); 102 rcu_idle_exit(); 103 tick_nohz_idle_exit(); 104 preempt_enable_no_resched(); 105 if (cpu_should_die()) 106 cpu_die(); 107 schedule(); 108 preempt_disable(); 109 } 110 } 111 112 113 /* 114 * cpu_idle_wait - Used to ensure that all the CPUs come out of the old 115 * idle loop and start using the new idle loop. 116 * Required while changing idle handler on SMP systems. 117 * Caller must have changed idle handler to the new value before the call. 118 * This window may be larger on shared systems. 119 */ 120 void cpu_idle_wait(void) 121 { 122 int cpu; 123 smp_mb(); 124 125 /* kick all the CPUs so that they exit out of old idle routine */ 126 get_online_cpus(); 127 for_each_online_cpu(cpu) { 128 if (cpu != smp_processor_id()) 129 smp_send_reschedule(cpu); 130 } 131 put_online_cpus(); 132 } 133 EXPORT_SYMBOL_GPL(cpu_idle_wait); 134 135 int powersave_nap; 136 137 #ifdef CONFIG_SYSCTL 138 /* 139 * Register the sysctl to set/clear powersave_nap. 140 */ 141 static ctl_table powersave_nap_ctl_table[]={ 142 { 143 .procname = "powersave-nap", 144 .data = &powersave_nap, 145 .maxlen = sizeof(int), 146 .mode = 0644, 147 .proc_handler = proc_dointvec, 148 }, 149 {} 150 }; 151 static ctl_table powersave_nap_sysctl_root[] = { 152 { 153 .procname = "kernel", 154 .mode = 0555, 155 .child = powersave_nap_ctl_table, 156 }, 157 {} 158 }; 159 160 static int __init 161 register_powersave_nap_sysctl(void) 162 { 163 register_sysctl_table(powersave_nap_sysctl_root); 164 165 return 0; 166 } 167 __initcall(register_powersave_nap_sysctl); 168 #endif 169