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