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 static int __init powersave_off(char *arg) 43 { 44 ppc_md.power_save = NULL; 45 return 0; 46 } 47 __setup("powersave=off", powersave_off); 48 49 #if defined(CONFIG_PPC_PSERIES) && defined(CONFIG_TRACEPOINTS) 50 static const bool idle_uses_rcu = 1; 51 #else 52 static const bool idle_uses_rcu; 53 #endif 54 55 /* 56 * The body of the idle task. 57 */ 58 void cpu_idle(void) 59 { 60 if (ppc_md.idle_loop) 61 ppc_md.idle_loop(); /* doesn't return */ 62 63 set_thread_flag(TIF_POLLING_NRFLAG); 64 while (1) { 65 if (idle_uses_rcu) 66 tick_nohz_idle_enter(); 67 else 68 tick_nohz_idle_enter_norcu(); 69 while (!need_resched() && !cpu_should_die()) { 70 ppc64_runlatch_off(); 71 72 if (ppc_md.power_save) { 73 clear_thread_flag(TIF_POLLING_NRFLAG); 74 /* 75 * smp_mb is so clearing of TIF_POLLING_NRFLAG 76 * is ordered w.r.t. need_resched() test. 77 */ 78 smp_mb(); 79 local_irq_disable(); 80 81 /* Don't trace irqs off for idle */ 82 stop_critical_timings(); 83 84 /* check again after disabling irqs */ 85 if (!need_resched() && !cpu_should_die()) 86 ppc_md.power_save(); 87 88 start_critical_timings(); 89 90 local_irq_enable(); 91 set_thread_flag(TIF_POLLING_NRFLAG); 92 93 } else { 94 /* 95 * Go into low thread priority and possibly 96 * low power mode. 97 */ 98 HMT_low(); 99 HMT_very_low(); 100 } 101 } 102 103 HMT_medium(); 104 ppc64_runlatch_on(); 105 if (idle_uses_rcu) 106 tick_nohz_idle_exit(); 107 else 108 tick_nohz_idle_exit_norcu(); 109 preempt_enable_no_resched(); 110 if (cpu_should_die()) 111 cpu_die(); 112 schedule(); 113 preempt_disable(); 114 } 115 } 116 117 int powersave_nap; 118 119 #ifdef CONFIG_SYSCTL 120 /* 121 * Register the sysctl to set/clear powersave_nap. 122 */ 123 static ctl_table powersave_nap_ctl_table[]={ 124 { 125 .procname = "powersave-nap", 126 .data = &powersave_nap, 127 .maxlen = sizeof(int), 128 .mode = 0644, 129 .proc_handler = proc_dointvec, 130 }, 131 {} 132 }; 133 static ctl_table powersave_nap_sysctl_root[] = { 134 { 135 .procname = "kernel", 136 .mode = 0555, 137 .child = powersave_nap_ctl_table, 138 }, 139 {} 140 }; 141 142 static int __init 143 register_powersave_nap_sysctl(void) 144 { 145 register_sysctl_table(powersave_nap_sysctl_root); 146 147 return 0; 148 } 149 __initcall(register_powersave_nap_sysctl); 150 #endif 151