arch/powerpc/kernel/idle.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Idle daemon for PowerPC.  Idle daemon will handle any action
   4  * that needs to be taken when the system becomes idle.
   5  *
   6  * Originally written by Cort Dougan (cort@cs.nmt.edu).
   7  * Subsequent 32-bit hacking by Tom Rini, Armin Kuster,
   8  * Paul Mackerras and others.
   9  *
  10  * iSeries supported added by Mike Corrigan <mikejc@us.ibm.com>
  11  *
  12  * Additional shared processor, SMT, and firmware support
  13  *    Copyright (c) 2003 Dave Engebretsen <engebret@us.ibm.com>
  14  *
  15  * 32-bit and 64-bit versions merged by Paul Mackerras <paulus@samba.org>
  16  */
  17
  18 #include <linux/sched.h>
  19 #include <linux/kernel.h>
  20 #include <linux/smp.h>
  21 #include <linux/cpu.h>
  22 #include <linux/sysctl.h>
  23 #include <linux/tick.h>
  24
  25 #include <asm/processor.h>
  26 #include <asm/cputable.h>
  27 #include <asm/time.h>
  28 #include <asm/machdep.h>
  29 #include <asm/runlatch.h>
  30 #include <asm/smp.h>
  31
  32
  33 unsigned long cpuidle_disable = IDLE_NO_OVERRIDE;
  34 EXPORT_SYMBOL(cpuidle_disable);
  35
  36 static int __init powersave_off(char *arg)
  37 {
  38         ppc_md.power_save = NULL;
  39         cpuidle_disable = IDLE_POWERSAVE_OFF;
  40         return 0;
  41 }
  42 __setup("powersave=off", powersave_off);
  43
  44 #ifdef CONFIG_HOTPLUG_CPU
  45 void arch_cpu_idle_dead(void)
  46 {
  47         sched_preempt_enable_no_resched();
  48         cpu_die();
  49 }
  50 #endif
  51
  52 void arch_cpu_idle(void)
  53 {
  54         ppc64_runlatch_off();
  55
  56         if (ppc_md.power_save) {
  57                 ppc_md.power_save();
  58                 /*
  59                  * Some power_save functions return with
  60                  * interrupts enabled, some don't.
  61                  */
  62                 if (irqs_disabled())
  63                         local_irq_enable();
  64         } else {
  65                 local_irq_enable();
  66                 /*
  67                  * Go into low thread priority and possibly
  68                  * low power mode.
  69                  */
  70                 HMT_low();
  71                 HMT_very_low();
  72         }
  73
  74         HMT_medium();
  75         ppc64_runlatch_on();
  76 }
  77
  78 int powersave_nap;
  79
  80 #ifdef CONFIG_PPC_970_NAP
  81 void power4_idle(void)
  82 {
  83         if (!cpu_has_feature(CPU_FTR_CAN_NAP))
  84                 return;
  85
  86         if (!powersave_nap)
  87                 return;
  88
  89         if (!prep_irq_for_idle())
  90                 return;
  91
  92         if (cpu_has_feature(CPU_FTR_ALTIVEC))
  93                 asm volatile("DSSALL ; sync" ::: "memory");
  94
  95         power4_idle_nap();
  96
  97         /*
  98          * power4_idle_nap returns with interrupts enabled (soft and hard).
  99          * to our caller with interrupts enabled (soft and hard). Our caller
 100          * can cope with either interrupts disabled or enabled upon return.
 101          */
 102 }
 103 #endif
 104
 105 #ifdef CONFIG_SYSCTL
 106 /*
 107  * Register the sysctl to set/clear powersave_nap.
 108  */
 109 static struct ctl_table powersave_nap_ctl_table[] = {
 110         {
 111                 .procname       = "powersave-nap",
 112                 .data           = &powersave_nap,
 113                 .maxlen         = sizeof(int),
 114                 .mode           = 0644,
 115                 .proc_handler   = proc_dointvec,
 116         },
 117         {}
 118 };
 119 static struct ctl_table powersave_nap_sysctl_root[] = {
 120         {
 121                 .procname       = "kernel",
 122                 .mode           = 0555,
 123                 .child          = powersave_nap_ctl_table,
 124         },
 125         {}
 126 };
 127
 128 static int __init
 129 register_powersave_nap_sysctl(void)
 130 {
 131         register_sysctl_table(powersave_nap_sysctl_root);
 132
 133         return 0;
 134 }
 135 __initcall(register_powersave_nap_sysctl);
 136 #endif