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 /* this is used for software suspend, and that shuts down 38 * CPUs even while the system is still booting... */ 39 #define cpu_should_die() (cpu_is_offline(smp_processor_id()) && \ 40 (system_state == SYSTEM_RUNNING \ 41 || system_state == SYSTEM_BOOTING)) 42 #else 43 #define cpu_should_die() 0 44 #endif 45 46 static int __init powersave_off(char *arg) 47 { 48 ppc_md.power_save = NULL; 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_stop_sched_tick(); 64 while (!need_resched() && !cpu_should_die()) { 65 ppc64_runlatch_off(); 66 67 if (ppc_md.power_save) { 68 clear_thread_flag(TIF_POLLING_NRFLAG); 69 /* 70 * smp_mb is so clearing of TIF_POLLING_NRFLAG 71 * is ordered w.r.t. need_resched() test. 72 */ 73 smp_mb(); 74 local_irq_disable(); 75 76 /* check again after disabling irqs */ 77 if (!need_resched() && !cpu_should_die()) 78 ppc_md.power_save(); 79 80 local_irq_enable(); 81 set_thread_flag(TIF_POLLING_NRFLAG); 82 83 } else { 84 /* 85 * Go into low thread priority and possibly 86 * low power mode. 87 */ 88 HMT_low(); 89 HMT_very_low(); 90 } 91 } 92 93 HMT_medium(); 94 ppc64_runlatch_on(); 95 tick_nohz_restart_sched_tick(); 96 if (cpu_should_die()) 97 cpu_die(); 98 preempt_enable_no_resched(); 99 schedule(); 100 preempt_disable(); 101 } 102 } 103 104 int powersave_nap; 105 106 #ifdef CONFIG_SYSCTL 107 /* 108 * Register the sysctl to set/clear powersave_nap. 109 */ 110 static ctl_table powersave_nap_ctl_table[]={ 111 { 112 .ctl_name = KERN_PPC_POWERSAVE_NAP, 113 .procname = "powersave-nap", 114 .data = &powersave_nap, 115 .maxlen = sizeof(int), 116 .mode = 0644, 117 .proc_handler = &proc_dointvec, 118 }, 119 {} 120 }; 121 static ctl_table powersave_nap_sysctl_root[] = { 122 { 123 .ctl_name = CTL_KERN, 124 .procname = "kernel", 125 .mode = 0755, 126 .child = powersave_nap_ctl_table, 127 }, 128 {} 129 }; 130 131 static int __init 132 register_powersave_nap_sysctl(void) 133 { 134 register_sysctl_table(powersave_nap_sysctl_root); 135 136 return 0; 137 } 138 __initcall(register_powersave_nap_sysctl); 139 #endif 140