USB: OTG: Take wakelock when VBUS present

Enabled by default, can disable with:
   echo N > /sys/module/otg_wakelock/parameters/enabled

Change-Id: I34974624c52ae23490852b44c270d2f326cf6116
Signed-off-by: Todd Poynor <toddpoynor@google.com>

drivers/usb/otg/Kconfig

@@ -12,6 +12,14 @@ config USB_OTG_UTILS
 	  Select this to make sure the build includes objects from
 	  the OTG infrastructure directory.
 
+config USB_OTG_WAKELOCK
+	bool "Hold a wakelock when USB connected"
+	depends on WAKELOCK
+	select USB_OTG_UTILS
+	help
+	  Select this to automatically hold a wakelock when USB is
+	  connected, preventing suspend.
+
 if USB || USB_GADGET
 
 #

drivers/usb/otg/Makefile

@@ -7,6 +7,7 @@ ccflags-$(CONFIG_USB_GADGET_DEBUG)	+= -DDEBUG
 
 # infrastructure
 obj-$(CONFIG_USB_OTG_UTILS)	+= otg.o
+obj-$(CONFIG_USB_OTG_WAKELOCK)	+= otg-wakelock.o
 
 # transceiver drivers
 obj-$(CONFIG_USB_GPIO_VBUS)	+= gpio_vbus.o

drivers/usb/otg/otg-wakelock.c

@@ -0,0 +1,190 @@
+/*
+ * 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/notifier.h>
+#include <linux/wakelock.h>
+#include <linux/spinlock.h>
+#include <linux/usb/otg.h>
+
+static bool enabled = true;
+static struct otg_transceiver *otgwl_xceiv;
+static struct notifier_block otgwl_nb;
+
+/*
+ * otgwl_spinlock is held while the VBUS lock is grabbed or dropped and the
+ * locked 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 wake_lock wakelock;
+	bool locked;
+};
+
+/*
+ * VBUS present lock.
+ */
+
+static struct otgwl_lock vbus_lock;
+
+static void otgwl_grab(struct otgwl_lock *lock)
+{
+	if (!lock->locked) {
+		wake_lock(&lock->wakelock);
+		lock->locked = true;
+	}
+}
+
+static void otgwl_drop(struct otgwl_lock *lock)
+{
+	if (lock->locked) {
+		wake_unlock(&lock->wakelock);
+		lock->locked = false;
+	}
+}
+
+static int otgwl_otg_notifications(struct notifier_block *nb,
+				   unsigned long event, void *unused)
+{
+	unsigned long irqflags;
+
+	if (!enabled)
+		return NOTIFY_OK;
+
+	spin_lock_irqsave(&otgwl_spinlock, irqflags);
+
+	switch (event) {
+	case USB_EVENT_VBUS:
+	case USB_EVENT_ENUMERATED:
+		otgwl_grab(&vbus_lock);
+		break;
+
+	case USB_EVENT_NONE:
+	case USB_EVENT_ID:
+	case USB_EVENT_CHARGER:
+		otgwl_drop(&vbus_lock);
+		break;
+
+	default:
+		break;
+	}
+
+	spin_unlock_irqrestore(&otgwl_spinlock, irqflags);
+	return NOTIFY_OK;
+}
+
+static void sync_with_xceiv_state(void)
+{
+	if ((otgwl_xceiv->last_event == USB_EVENT_VBUS) ||
+	    (otgwl_xceiv->last_event == USB_EVENT_ENUMERATED))
+		otgwl_grab(&vbus_lock);
+	else
+		otgwl_drop(&vbus_lock);
+}
+
+static int init_for_xceiv(void)
+{
+	int rv;
+
+	if (!otgwl_xceiv) {
+		otgwl_xceiv = otg_get_transceiver();
+
+		if (!otgwl_xceiv) {
+			pr_err("%s: No OTG transceiver found\n", __func__);
+			return -ENODEV;
+		}
+
+		snprintf(vbus_lock.name, sizeof(vbus_lock.name), "vbus-%s",
+			 dev_name(otgwl_xceiv->dev));
+		wake_lock_init(&vbus_lock.wakelock, WAKE_LOCK_SUSPEND,
+			       vbus_lock.name);
+
+		rv = otg_register_notifier(otgwl_xceiv, &otgwl_nb);
+
+		if (rv) {
+			pr_err("%s: otg_register_notifier on transceiver %s"
+			       " failed\n", __func__,
+			       dev_name(otgwl_xceiv->dev));
+			otgwl_xceiv = NULL;
+			wake_lock_destroy(&vbus_lock.wakelock);
+			return rv;
+		}
+	}
+
+	return 0;
+}
+
+static int set_enabled(const char *val, const struct kernel_param *kp)
+{
+	unsigned long irqflags;
+	int rv = param_set_bool(val, kp);
+
+	if (rv)
+		return rv;
+
+	rv = init_for_xceiv();
+
+	if (rv)
+		return rv;
+
+	spin_lock_irqsave(&otgwl_spinlock, irqflags);
+
+	if (enabled)
+		sync_with_xceiv_state();
+	else
+		otgwl_drop(&vbus_lock);
+
+	spin_unlock_irqrestore(&otgwl_spinlock, irqflags);
+	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)
+{
+	unsigned long irqflags;
+
+	otgwl_nb.notifier_call = otgwl_otg_notifications;
+
+	if (!init_for_xceiv()) {
+		spin_lock_irqsave(&otgwl_spinlock, irqflags);
+
+		if (enabled)
+			sync_with_xceiv_state();
+
+		spin_unlock_irqrestore(&otgwl_spinlock, irqflags);
+	} else {
+		enabled = false;
+	}
+
+	return 0;
+}
+
+late_initcall(otg_wakelock_init);