arch/s390/kernel/idle.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Idle functions for s390.
   4  *
   5  * Copyright IBM Corp. 2014
   6  *
   7  * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/kernel_stat.h>
  12 #include <linux/kprobes.h>
  13 #include <linux/notifier.h>
  14 #include <linux/init.h>
  15 #include <linux/cpu.h>
  16 #include <linux/sched/cputime.h>
  17 #include <asm/nmi.h>
  18 #include <asm/smp.h>
  19 #include "entry.h"
  20
  21 static DEFINE_PER_CPU(struct s390_idle_data, s390_idle);
  22
  23 void enabled_wait(void)
  24 {
  25         struct s390_idle_data *idle = this_cpu_ptr(&s390_idle);
  26         unsigned long long idle_time;
  27         unsigned long psw_mask;
  28
  29         trace_hardirqs_on();
  30
  31         /* Wait for external, I/O or machine check interrupt. */
  32         psw_mask = PSW_KERNEL_BITS | PSW_MASK_WAIT | PSW_MASK_DAT |
  33                 PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
  34         clear_cpu_flag(CIF_NOHZ_DELAY);
  35
  36         /* Call the assembler magic in entry.S */
  37         psw_idle(idle, psw_mask);
  38
  39         trace_hardirqs_off();
  40
  41         /* Account time spent with enabled wait psw loaded as idle time. */
  42         write_seqcount_begin(&idle->seqcount);
  43         idle_time = idle->clock_idle_exit - idle->clock_idle_enter;
  44         idle->clock_idle_enter = idle->clock_idle_exit = 0ULL;
  45         idle->idle_time += idle_time;
  46         idle->idle_count++;
  47         account_idle_time(cputime_to_nsecs(idle_time));
  48         write_seqcount_end(&idle->seqcount);
  49 }
  50 NOKPROBE_SYMBOL(enabled_wait);
  51
  52 static ssize_t show_idle_count(struct device *dev,
  53                                 struct device_attribute *attr, char *buf)
  54 {
  55         struct s390_idle_data *idle = &per_cpu(s390_idle, dev->id);
  56         unsigned long long idle_count;
  57         unsigned int seq;
  58
  59         do {
  60                 seq = read_seqcount_begin(&idle->seqcount);
  61                 idle_count = READ_ONCE(idle->idle_count);
  62                 if (READ_ONCE(idle->clock_idle_enter))
  63                         idle_count++;
  64         } while (read_seqcount_retry(&idle->seqcount, seq));
  65         return sprintf(buf, "%llu\n", idle_count);
  66 }
  67 DEVICE_ATTR(idle_count, 0444, show_idle_count, NULL);
  68
  69 static ssize_t show_idle_time(struct device *dev,
  70                                 struct device_attribute *attr, char *buf)
  71 {
  72         struct s390_idle_data *idle = &per_cpu(s390_idle, dev->id);
  73         unsigned long long now, idle_time, idle_enter, idle_exit;
  74         unsigned int seq;
  75
  76         do {
  77                 now = get_tod_clock();
  78                 seq = read_seqcount_begin(&idle->seqcount);
  79                 idle_time = READ_ONCE(idle->idle_time);
  80                 idle_enter = READ_ONCE(idle->clock_idle_enter);
  81                 idle_exit = READ_ONCE(idle->clock_idle_exit);
  82         } while (read_seqcount_retry(&idle->seqcount, seq));
  83         idle_time += idle_enter ? ((idle_exit ? : now) - idle_enter) : 0;
  84         return sprintf(buf, "%llu\n", idle_time >> 12);
  85 }
  86 DEVICE_ATTR(idle_time_us, 0444, show_idle_time, NULL);
  87
  88 u64 arch_cpu_idle_time(int cpu)
  89 {
  90         struct s390_idle_data *idle = &per_cpu(s390_idle, cpu);
  91         unsigned long long now, idle_enter, idle_exit;
  92         unsigned int seq;
  93
  94         do {
  95                 now = get_tod_clock();
  96                 seq = read_seqcount_begin(&idle->seqcount);
  97                 idle_enter = READ_ONCE(idle->clock_idle_enter);
  98                 idle_exit = READ_ONCE(idle->clock_idle_exit);
  99         } while (read_seqcount_retry(&idle->seqcount, seq));
 100
 101         return cputime_to_nsecs(idle_enter ? ((idle_exit ?: now) - idle_enter) : 0);
 102 }
 103
 104 void arch_cpu_idle_enter(void)
 105 {
 106         local_mcck_disable();
 107 }
 108
 109 void arch_cpu_idle(void)
 110 {
 111         if (!test_cpu_flag(CIF_MCCK_PENDING))
 112                 /* Halt the cpu and keep track of cpu time accounting. */
 113                 enabled_wait();
 114         local_irq_enable();
 115 }
 116
 117 void arch_cpu_idle_exit(void)
 118 {
 119         local_mcck_enable();
 120         if (test_cpu_flag(CIF_MCCK_PENDING))
 121                 s390_handle_mcck();
 122 }
 123
 124 void arch_cpu_idle_dead(void)
 125 {
 126         cpu_die();
 127 }