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 42static 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/* 50 * The body of the idle task. 51 */ 52void cpu_idle(void) 53{ 54 if (ppc_md.idle_loop) 55 ppc_md.idle_loop(); /* doesn't return */ 56 57 set_thread_flag(TIF_POLLING_NRFLAG); 58 while (1) { 59 tick_nohz_stop_sched_tick(1); 60 while (!need_resched() && !cpu_should_die()) { 61 ppc64_runlatch_off(); 62 63 if (ppc_md.power_save) { 64 clear_thread_flag(TIF_POLLING_NRFLAG); 65 /* 66 * smp_mb is so clearing of TIF_POLLING_NRFLAG 67 * is ordered w.r.t. need_resched() test. 68 */ 69 smp_mb(); 70 local_irq_disable(); 71 72 /* Don't trace irqs off for idle */ 73 stop_critical_timings(); 74 75 /* check again after disabling irqs */ 76 if (!need_resched() && !cpu_should_die()) 77 ppc_md.power_save(); 78 79 start_critical_timings(); 80 81 local_irq_enable(); 82 set_thread_flag(TIF_POLLING_NRFLAG); 83 84 } else { 85 /* 86 * Go into low thread priority and possibly 87 * low power mode. 88 */ 89 HMT_low(); 90 HMT_very_low(); 91 } 92 } 93 94 HMT_medium(); 95 ppc64_runlatch_on(); 96 tick_nohz_restart_sched_tick(); 97 preempt_enable_no_resched(); 98 if (cpu_should_die()) 99 cpu_die(); 100 schedule(); 101 preempt_disable(); 102 } 103} 104 105int powersave_nap; 106 107#ifdef CONFIG_SYSCTL 108/* 109 * Register the sysctl to set/clear powersave_nap. 110 */ 111static ctl_table powersave_nap_ctl_table[]={ 112 { 113 .procname = "powersave-nap", 114 .data = &powersave_nap, 115 .maxlen = sizeof(int), 116 .mode = 0644, 117 .proc_handler = proc_dointvec, 118 }, 119 {} 120}; 121static ctl_table powersave_nap_sysctl_root[] = { 122 { 123 .procname = "kernel", 124 .mode = 0555, 125 .child = powersave_nap_ctl_table, 126 }, 127 {} 128}; 129 130static int __init 131register_powersave_nap_sysctl(void) 132{ 133 register_sysctl_table(powersave_nap_sysctl_root); 134 135 return 0; 136} 137__initcall(register_powersave_nap_sysctl); 138#endif 139