linux_kernel/drivers/cpuidle/cpuidle-arm64.c

/*
 * ARM64 generic CPU idle driver.
 *
 * Copyright (C) 2014 ARM Ltd.
 * Author: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#define pr_fmt(fmt) "CPUidle arm64: " fmt

#include <linux/cpuidle.h>
#include <linux/cpumask.h>
#include <linux/cpu_pm.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>

#include <asm/cpuidle.h>
#include <asm/suspend.h>

#include "dt_idle_states.h"

/*
 * arm64_enter_idle_state - Programs CPU to enter the specified state
 *
 * dev: cpuidle device
 * drv: cpuidle driver
 * idx: state index
 *
 * Called from the CPUidle framework to program the device to the
 * specified target state selected by the governor.
 */
static int arm64_enter_idle_state(struct cpuidle_device *dev,
				  struct cpuidle_driver *drv, int idx)
{
	int ret;

	if (!idx) {
		cpu_do_idle();
		return idx;
	}

	ret = cpu_pm_enter();
	if (!ret) {
		/*
		 * Pass idle state index to cpu_suspend which in turn will
		 * call the CPU ops suspend protocol with idle index as a
		 * parameter.
		 */
		ret = cpu_suspend(idx);

		cpu_pm_exit();
	}

	return ret ? -1 : idx;
}

static struct cpuidle_driver arm64_idle_driver = {
	.name = "arm64_idle",
	.owner = THIS_MODULE,
	/*
	 * State at index 0 is standby wfi and considered standard
	 * on all ARM platforms. If in some platforms simple wfi
	 * can't be used as "state 0", DT bindings must be implemented
	 * to work around this issue and allow installing a special
	 * handler for idle state index 0.
	 */
	.states[0] = {
		.enter                  = arm64_enter_idle_state,
		.exit_latency           = 1,
		.target_residency       = 1,
		.power_usage		= UINT_MAX,
		.flags                  = CPUIDLE_FLAG_TIME_VALID,
		.name                   = "WFI",
		.desc                   = "ARM64 WFI",
	}
};

static const struct of_device_id arm64_idle_state_match[] __initconst = {
	{ .compatible = "arm,idle-state",
	  .data = arm64_enter_idle_state },
	{ },
};

/*
 * arm64_idle_init
 *
 * Registers the arm64 specific cpuidle driver with the cpuidle
 * framework. It relies on core code to parse the idle states
 * and initialize them using driver data structures accordingly.
 */
static int __init arm64_idle_init(void)
{
	int cpu, ret;
	struct cpuidle_driver *drv = &arm64_idle_driver;

	/*
	 * Initialize idle states data, starting at index 1.
	 * This driver is DT only, if no DT idle states are detected (ret == 0)
	 * let the driver initialization fail accordingly since there is no
	 * reason to initialize the idle driver if only wfi is supported.
	 */
	ret = dt_init_idle_driver(drv, arm64_idle_state_match, 1);
	if (ret <= 0) {
		if (ret)
			pr_err("failed to initialize idle states\n");
		return ret ? : -ENODEV;
	}

	/*
	 * Call arch CPU operations in order to initialize
	 * idle states suspend back-end specific data
	 */
	for_each_possible_cpu(cpu) {
		ret = cpu_init_idle(cpu);
		if (ret) {
			pr_err("CPU %d failed to init idle CPU ops\n", cpu);
			return ret;
		}
	}

	ret = cpuidle_register(drv, NULL);
	if (ret) {
		pr_err("failed to register cpuidle driver\n");
		return ret;
	}

	return 0;
}
device_initcall(arm64_idle_init);