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/processor.h> 30 #include <asm/cputable.h> 31 #include <asm/time.h> 32 #include <asm/machdep.h> 33 #include <asm/runlatch.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 set_thread_flag(TIF_POLLING_NRFLAG); 59 while (1) { 60 tick_nohz_idle_enter(); 61 rcu_idle_enter(); 62 63 while (!need_resched() && !cpu_should_die()) { 64 ppc64_runlatch_off(); 65 66 if (ppc_md.power_save) { 67 clear_thread_flag(TIF_POLLING_NRFLAG); 68 /* 69 * smp_mb is so clearing of TIF_POLLING_NRFLAG 70 * is ordered w.r.t. need_resched() test. 71 */ 72 smp_mb(); 73 local_irq_disable(); 74 75 /* Don't trace irqs off for idle */ 76 stop_critical_timings(); 77 78 /* check again after disabling irqs */ 79 if (!need_resched() && !cpu_should_die()) 80 ppc_md.power_save(); 81 82 start_critical_timings(); 83 84 /* Some power_save functions return with 85 * interrupts enabled, some don't. 86 */ 87 if (irqs_disabled()) 88 local_irq_enable(); 89 set_thread_flag(TIF_POLLING_NRFLAG); 90 91 } else { 92 /* 93 * Go into low thread priority and possibly 94 * low power mode. 95 */ 96 HMT_low(); 97 HMT_very_low(); 98 } 99 } 100 101 HMT_medium(); 102 ppc64_runlatch_on(); 103 rcu_idle_exit(); 104 tick_nohz_idle_exit(); 105 if (cpu_should_die()) { 106 sched_preempt_enable_no_resched(); 107 cpu_die(); 108 } 109 schedule_preempt_disabled(); 110 } 111 } 112 113 int powersave_nap; 114 115 #ifdef CONFIG_SYSCTL 116 /* 117 * Register the sysctl to set/clear powersave_nap. 118 */ 119 static ctl_table powersave_nap_ctl_table[]={ 120 { 121 .procname = "powersave-nap", 122 .data = &powersave_nap, 123 .maxlen = sizeof(int), 124 .mode = 0644, 125 .proc_handler = proc_dointvec, 126 }, 127 {} 128 }; 129 static ctl_table powersave_nap_sysctl_root[] = { 130 { 131 .procname = "kernel", 132 .mode = 0555, 133 .child = powersave_nap_ctl_table, 134 }, 135 {} 136 }; 137 138 static int __init 139 register_powersave_nap_sysctl(void) 140 { 141 register_sysctl_table(powersave_nap_sysctl_root); 142 143 return 0; 144 } 145 __initcall(register_powersave_nap_sysctl); 146 #endif 147