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 28 #include <asm/system.h> 29 #include <asm/processor.h> 30 #include <asm/cputable.h> 31 #include <asm/time.h> 32 #include <asm/machdep.h> 33 #include <asm/smp.h> 34 35 #ifdef CONFIG_HOTPLUG_CPU 36 #define cpu_should_die() (cpu_is_offline(smp_processor_id()) && \ 37 system_state == SYSTEM_RUNNING) 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 while (!need_resched() && !cpu_should_die()) { 60 ppc64_runlatch_off(); 61 62 if (ppc_md.power_save) { 63 clear_thread_flag(TIF_POLLING_NRFLAG); 64 /* 65 * smp_mb is so clearing of TIF_POLLING_NRFLAG 66 * is ordered w.r.t. need_resched() test. 67 */ 68 smp_mb(); 69 local_irq_disable(); 70 71 /* check again after disabling irqs */ 72 if (!need_resched() && !cpu_should_die()) 73 ppc_md.power_save(); 74 75 local_irq_enable(); 76 set_thread_flag(TIF_POLLING_NRFLAG); 77 78 } else { 79 /* 80 * Go into low thread priority and possibly 81 * low power mode. 82 */ 83 HMT_low(); 84 HMT_very_low(); 85 } 86 } 87 88 HMT_medium(); 89 ppc64_runlatch_on(); 90 if (cpu_should_die()) 91 cpu_die(); 92 preempt_enable_no_resched(); 93 schedule(); 94 preempt_disable(); 95 } 96 } 97 98 int powersave_nap; 99 100 #ifdef CONFIG_SYSCTL 101 /* 102 * Register the sysctl to set/clear powersave_nap. 103 */ 104 static ctl_table powersave_nap_ctl_table[]={ 105 { 106 .ctl_name = KERN_PPC_POWERSAVE_NAP, 107 .procname = "powersave-nap", 108 .data = &powersave_nap, 109 .maxlen = sizeof(int), 110 .mode = 0644, 111 .proc_handler = &proc_dointvec, 112 }, 113 {} 114 }; 115 static ctl_table powersave_nap_sysctl_root[] = { 116 { 117 .ctl_name = CTL_KERN, 118 .procname = "kernel", 119 .mode = 0755, 120 .child = powersave_nap_ctl_table, 121 }, 122 {} 123 }; 124 125 static int __init 126 register_powersave_nap_sysctl(void) 127 { 128 register_sysctl_table(powersave_nap_sysctl_root); 129 130 return 0; 131 } 132 __initcall(register_powersave_nap_sysctl); 133 #endif 134