otg-wakelock.c
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/*
* otg-wakelock.c
*
* Copyright (C) 2011 Google, Inc.
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*/
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/spinlock.h>
#include <linux/usb/otg.h>
#include <linux/usb/gadget.h>
#define TEMPORARY_HOLD_TIME 2000
static bool enabled = true;
static struct notifier_block otgwl_nb;
/*
* otgwl_spinlock is held while the VBUS lock is grabbed or dropped and the
* held field is updated to match.
*/
static DEFINE_SPINLOCK(otgwl_spinlock);
/*
* Only one lock, but since these 3 fields are associated with each other...
*/
struct otgwl_lock {
char name[40];
struct wakeup_source wakesrc;
bool held;
};
/*
* VBUS present lock. Also used as a timed lock on charger
* connect/disconnect and USB host disconnect, to allow the system
* to react to the change in power.
*/
static struct otgwl_lock vbus_lock;
static void otgwl_hold(struct otgwl_lock *lock)
{
if (!lock->held) {
__pm_stay_awake(&lock->wakesrc);
lock->held = true;
}
}
static void otgwl_temporary_hold(struct otgwl_lock *lock)
{
__pm_wakeup_event(&lock->wakesrc, TEMPORARY_HOLD_TIME);
lock->held = false;
}
static void otgwl_drop(struct otgwl_lock *lock)
{
if (lock->held) {
__pm_relax(&lock->wakesrc);
lock->held = false;
}
}
static void otgwl_handle_event(unsigned long event)
{
unsigned long irqflags;
spin_lock_irqsave(&otgwl_spinlock, irqflags);
if (!enabled) {
otgwl_drop(&vbus_lock);
spin_unlock_irqrestore(&otgwl_spinlock, irqflags);
return;
}
switch (event) {
case USB_EVENT_VBUS:
case USB_EVENT_ENUMERATED:
otgwl_hold(&vbus_lock);
break;
case USB_EVENT_NONE:
case USB_EVENT_ID:
case USB_EVENT_CHARGER:
otgwl_temporary_hold(&vbus_lock);
break;
case USB_EVENT_DISCONNECT:
otgwl_drop(&vbus_lock);
break;
default:
break;
}
spin_unlock_irqrestore(&otgwl_spinlock, irqflags);
}
static int otgwl_otg_notifications(struct notifier_block *nb,
unsigned long event, void *unused)
{
otgwl_handle_event(event);
return NOTIFY_OK;
}
static int set_enabled(const char *val, const struct kernel_param *kp)
{
int rv = param_set_bool(val, kp);
if (rv)
return rv;
return 0;
}
static struct kernel_param_ops enabled_param_ops = {
.set = set_enabled,
.get = param_get_bool,
};
module_param_cb(enabled, &enabled_param_ops, &enabled, 0644);
MODULE_PARM_DESC(enabled, "enable wakelock when VBUS present");
static int __init otg_wakelock_init(void)
{
int ret;
snprintf(vbus_lock.name, sizeof(vbus_lock.name), "vbus-%s",
"wakelock");
wakeup_source_init(&vbus_lock.wakesrc, vbus_lock.name);
otgwl_nb.notifier_call = otgwl_otg_notifications;
ret = register_usb_gadget_notifier(&otgwl_nb);
if (ret) {
pr_err("%s: usb_register_notifier"
" failed\n", __func__);
wakeup_source_trash(&vbus_lock.wakesrc);
return ret;
}
return ret;
}
late_initcall(otg_wakelock_init);