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/config.h> 23 #include <linux/sched.h> 24 #include <linux/kernel.h> 25 #include <linux/smp.h> 26 #include <linux/cpu.h> 27 #include <linux/sysctl.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 system_state == SYSTEM_RUNNING) 39 #else 40 #define cpu_should_die() 0 41 #endif 42 43 /* 44 * The body of the idle task. 45 */ 46 void cpu_idle(void) 47 { 48 if (ppc_md.idle_loop) 49 ppc_md.idle_loop(); /* doesn't return */ 50 51 set_thread_flag(TIF_POLLING_NRFLAG); 52 while (1) { 53 while (!need_resched() && !cpu_should_die()) { 54 ppc64_runlatch_off(); 55 56 if (ppc_md.power_save) { 57 clear_thread_flag(TIF_POLLING_NRFLAG); 58 /* 59 * smp_mb is so clearing of TIF_POLLING_NRFLAG 60 * is ordered w.r.t. need_resched() test. 61 */ 62 smp_mb(); 63 local_irq_disable(); 64 65 /* check again after disabling irqs */ 66 if (!need_resched() && !cpu_should_die()) 67 ppc_md.power_save(); 68 69 local_irq_enable(); 70 set_thread_flag(TIF_POLLING_NRFLAG); 71 72 } else { 73 /* 74 * Go into low thread priority and possibly 75 * low power mode. 76 */ 77 HMT_low(); 78 HMT_very_low(); 79 } 80 } 81 82 HMT_medium(); 83 ppc64_runlatch_on(); 84 if (cpu_should_die()) 85 cpu_die(); 86 preempt_enable_no_resched(); 87 schedule(); 88 preempt_disable(); 89 } 90 } 91 92 int powersave_nap; 93 94 #ifdef CONFIG_SYSCTL 95 /* 96 * Register the sysctl to set/clear powersave_nap. 97 */ 98 static ctl_table powersave_nap_ctl_table[]={ 99 { 100 .ctl_name = KERN_PPC_POWERSAVE_NAP, 101 .procname = "powersave-nap", 102 .data = &powersave_nap, 103 .maxlen = sizeof(int), 104 .mode = 0644, 105 .proc_handler = &proc_dointvec, 106 }, 107 { 0, }, 108 }; 109 static ctl_table powersave_nap_sysctl_root[] = { 110 { 1, "kernel", NULL, 0, 0755, powersave_nap_ctl_table, }, 111 { 0,}, 112 }; 113 114 static int __init 115 register_powersave_nap_sysctl(void) 116 { 117 register_sysctl_table(powersave_nap_sysctl_root, 0); 118 119 return 0; 120 } 121 __initcall(register_powersave_nap_sysctl); 122 #endif 123