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 /* 50 * The body of the idle task. 51 */ 52 void 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 /* check again after disabling irqs */ 73 if (!need_resched() && !cpu_should_die()) 74 ppc_md.power_save(); 75 76 local_irq_enable(); 77 set_thread_flag(TIF_POLLING_NRFLAG); 78 79 } else { 80 /* 81 * Go into low thread priority and possibly 82 * low power mode. 83 */ 84 HMT_low(); 85 HMT_very_low(); 86 } 87 } 88 89 HMT_medium(); 90 ppc64_runlatch_on(); 91 tick_nohz_restart_sched_tick(); 92 if (cpu_should_die()) 93 cpu_die(); 94 preempt_enable_no_resched(); 95 schedule(); 96 preempt_disable(); 97 } 98 } 99 100 int powersave_nap; 101 102 #ifdef CONFIG_SYSCTL 103 /* 104 * Register the sysctl to set/clear powersave_nap. 105 */ 106 static ctl_table powersave_nap_ctl_table[]={ 107 { 108 .ctl_name = KERN_PPC_POWERSAVE_NAP, 109 .procname = "powersave-nap", 110 .data = &powersave_nap, 111 .maxlen = sizeof(int), 112 .mode = 0644, 113 .proc_handler = &proc_dointvec, 114 }, 115 {} 116 }; 117 static ctl_table powersave_nap_sysctl_root[] = { 118 { 119 .ctl_name = CTL_KERN, 120 .procname = "kernel", 121 .mode = 0555, 122 .child = powersave_nap_ctl_table, 123 }, 124 {} 125 }; 126 127 static int __init 128 register_powersave_nap_sysctl(void) 129 { 130 register_sysctl_table(powersave_nap_sysctl_root); 131 132 return 0; 133 } 134 __initcall(register_powersave_nap_sysctl); 135 #endif 136