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}