1/*
2 * ARM64 generic CPU idle driver.
3 *
4 * Copyright (C) 2014 ARM Ltd.
5 * Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
11
12#define pr_fmt(fmt) "CPUidle arm64: " fmt
13
14#include <linux/cpuidle.h>
15#include <linux/cpumask.h>
16#include <linux/cpu_pm.h>
17#include <linux/kernel.h>
18#include <linux/module.h>
19#include <linux/of.h>
20
21#include <asm/cpuidle.h>
22#include <asm/suspend.h>
23
24#include "dt_idle_states.h"
25
26/*
27 * arm64_enter_idle_state - Programs CPU to enter the specified state
28 *
29 * dev: cpuidle device
30 * drv: cpuidle driver
31 * idx: state index
32 *
33 * Called from the CPUidle framework to program the device to the
34 * specified target state selected by the governor.
35 */
36static int arm64_enter_idle_state(struct cpuidle_device *dev,
37				  struct cpuidle_driver *drv, int idx)
38{
39	int ret;
40
41	if (!idx) {
42		cpu_do_idle();
43		return idx;
44	}
45
46	ret = cpu_pm_enter();
47	if (!ret) {
48		/*
49		 * Pass idle state index to cpu_suspend which in turn will
50		 * call the CPU ops suspend protocol with idle index as a
51		 * parameter.
52		 */
53		ret = cpu_suspend(idx);
54
55		cpu_pm_exit();
56	}
57
58	return ret ? -1 : idx;
59}
60
61static struct cpuidle_driver arm64_idle_driver = {
62	.name = "arm64_idle",
63	.owner = THIS_MODULE,
64	/*
65	 * State at index 0 is standby wfi and considered standard
66	 * on all ARM platforms. If in some platforms simple wfi
67	 * can't be used as "state 0", DT bindings must be implemented
68	 * to work around this issue and allow installing a special
69	 * handler for idle state index 0.
70	 */
71	.states[0] = {
72		.enter                  = arm64_enter_idle_state,
73		.exit_latency           = 1,
74		.target_residency       = 1,
75		.power_usage		= UINT_MAX,
76		.flags                  = CPUIDLE_FLAG_TIME_VALID,
77		.name                   = "WFI",
78		.desc                   = "ARM64 WFI",
79	}
80};
81
82static const struct of_device_id arm64_idle_state_match[] __initconst = {
83	{ .compatible = "arm,idle-state",
84	  .data = arm64_enter_idle_state },
85	{ },
86};
87
88/*
89 * arm64_idle_init
90 *
91 * Registers the arm64 specific cpuidle driver with the cpuidle
92 * framework. It relies on core code to parse the idle states
93 * and initialize them using driver data structures accordingly.
94 */
95static int __init arm64_idle_init(void)
96{
97	int cpu, ret;
98	struct cpuidle_driver *drv = &arm64_idle_driver;
99
100	/*
101	 * Initialize idle states data, starting at index 1.
102	 * This driver is DT only, if no DT idle states are detected (ret == 0)
103	 * let the driver initialization fail accordingly since there is no
104	 * reason to initialize the idle driver if only wfi is supported.
105	 */
106	ret = dt_init_idle_driver(drv, arm64_idle_state_match, 1);
107	if (ret <= 0) {
108		if (ret)
109			pr_err("failed to initialize idle states\n");
110		return ret ? : -ENODEV;
111	}
112
113	/*
114	 * Call arch CPU operations in order to initialize
115	 * idle states suspend back-end specific data
116	 */
117	for_each_possible_cpu(cpu) {
118		ret = cpu_init_idle(cpu);
119		if (ret) {
120			pr_err("CPU %d failed to init idle CPU ops\n", cpu);
121			return ret;
122		}
123	}
124
125	ret = cpuidle_register(drv, NULL);
126	if (ret) {
127		pr_err("failed to register cpuidle driver\n");
128		return ret;
129	}
130
131	return 0;
132}
133device_initcall(arm64_idle_init);
134