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/*
* 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.
*/
#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/psci.h>
#include <asm/suspend.h>
#include "of_idle_states.h"
typedef int (*suspend_init_fn)(struct cpuidle_driver *,
struct device_node *[]);
struct cpu_suspend_ops {
const char *id;
suspend_init_fn init_fn;
};
static const struct cpu_suspend_ops suspend_operations[] __initconst = {
{"arm,psci", psci_dt_register_idle_states},
{}
};
static __init const struct cpu_suspend_ops *get_suspend_ops(const char *str)
{
int i;
if (!str)
return NULL;
for (i = 0; suspend_operations[i].id; i++)
if (!strcmp(suspend_operations[i].id, str))
return &suspend_operations[i];
return NULL;
}
/*
* arm_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 arm_enter_idle_state(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int idx)
{
int ret;
if (!idx) {
cpu_do_idle();
return idx;
}
cpu_pm_enter();
/*
* Pass idle state index to cpu_suspend which in turn will call
* the CPU ops suspend protocol with idle index as a parameter.
*
* Some states would not require context to be saved and flushed
* to DRAM, so calling cpu_suspend would not be stricly necessary.
* When power domains specifications for ARM CPUs are finalized then
* this code can be optimized to prevent saving registers if not
* needed.
*/
ret = cpu_suspend(idx);
cpu_pm_exit();
return ret ? -1 : idx;
}
struct cpuidle_driver arm64_idle_driver = {
.name = "arm64_idle",
.owner = THIS_MODULE,
};
static struct device_node *state_nodes[CPUIDLE_STATE_MAX] __initdata;
/*
* 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 i, ret;
const char *entry_method;
struct device_node *idle_states_node;
const struct cpu_suspend_ops *suspend_init;
struct cpuidle_driver *drv = &arm64_idle_driver;
idle_states_node = of_find_node_by_path("/cpus/idle-states");
if (!idle_states_node)
return -ENOENT;
if (of_property_read_string(idle_states_node, "entry-method",
&entry_method)) {
pr_warn(" * %s missing entry-method property\n",
idle_states_node->full_name);
of_node_put(idle_states_node);
return -EOPNOTSUPP;
}
suspend_init = get_suspend_ops(entry_method);
if (!suspend_init) {
pr_warn("Missing suspend initializer\n");
of_node_put(idle_states_node);
return -EOPNOTSUPP;
}
/*
* 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.
*/
drv->states[0].exit_latency = 1;
drv->states[0].target_residency = 1;
drv->states[0].flags = CPUIDLE_FLAG_TIME_VALID;
strncpy(drv->states[0].name, "ARM WFI", CPUIDLE_NAME_LEN);
strncpy(drv->states[0].desc, "ARM WFI", CPUIDLE_DESC_LEN);
drv->cpumask = (struct cpumask *) cpu_possible_mask;
/*
* Start at index 1, request idle state nodes to be filled
*/
ret = of_init_idle_driver(drv, state_nodes, 1, true);
if (ret)
return ret;
if (suspend_init->init_fn(drv, state_nodes))
return -EOPNOTSUPP;
for (i = 0; i < drv->state_count; i++)
drv->states[i].enter = arm_enter_idle_state;
return cpuidle_register(drv, NULL);
}
device_initcall(arm64_idle_init);
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