LXR linux/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
  21static DEFINE_PER_CPU(struct s390_idle_data, s390_idle);
  22
  23void 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}
  50NOKPROBE_SYMBOL(enabled_wait);
  51
  52static 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}
  67DEVICE_ATTR(idle_count, 0444, show_idle_count, NULL);
  68
  69static 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}
  86DEVICE_ATTR(idle_time_us, 0444, show_idle_time, NULL);
  87
  88u64 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
 104void arch_cpu_idle_enter(void)
 105{
 106        local_mcck_disable();
 107}
 108
 109void 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
 117void arch_cpu_idle_exit(void)
 118{
 119        local_mcck_enable();
 120        if (test_cpu_flag(CIF_MCCK_PENDING))
 121                s390_handle_mcck();
 122}
 123
 124void arch_cpu_idle_dead(void)
 125{
 126        cpu_die();
 127}
 128