Power: add an API to log wakeup reasons

Add API log_wakeup_reason() and expose it to userspace via sysfs path
/sys/kernel/wakeup_reasons/last_resume_reason

Change-Id: I81addaf420f1338255c5d0638b0d244a99d777d1
Signed-off-by: Ruchi Kandoi <kandoiruchi@google.com>

include/linux/wakeup_reason.h

@@ -0,0 +1,23 @@
+/*
+ * include/linux/wakeup_reason.h
+ *
+ * Logs the reason which caused the kernel to resume
+ * from the suspend mode.
+ *
+ * Copyright (C) 2014 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.
+ */
+
+#ifndef _LINUX_WAKEUP_REASON_H
+#define _LINUX_WAKEUP_REASON_H
+
+void log_wakeup_reason(int irq);
+
+#endif /* _LINUX_WAKEUP_REASON_H */

kernel/power/Makefile

@@ -12,3 +12,5 @@ obj-$(CONFIG_PM_AUTOSLEEP)	+= autosleep.o
 obj-$(CONFIG_PM_WAKELOCKS)	+= wakelock.o
 
 obj-$(CONFIG_MAGIC_SYSRQ)	+= poweroff.o
+
+obj-$(CONFIG_SUSPEND)	+= wakeup_reason.o

kernel/power/wakeup_reason.c

@@ -0,0 +1,132 @@
+/*
+ * kernel/power/wakeup_reason.c
+ *
+ * Logs the reasons which caused the kernel to resume from
+ * the suspend mode.
+ *
+ * Copyright (C) 2014 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/wakeup_reason.h>
+#include <linux/kernel.h>
+#include <linux/irq.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/notifier.h>
+#include <linux/suspend.h>
+
+
+#define MAX_WAKEUP_REASON_IRQS 32
+static int irq_list[MAX_WAKEUP_REASON_IRQS];
+static int irq_count;
+static struct kobject *wakeup_reason;
+static spinlock_t resume_reason_lock;
+
+static ssize_t reason_show(struct kobject *kobj, struct kobj_attribute *attr,
+		const char *buf, size_t count)
+{
+	int irq_no, buf_offset = 0;
+	struct irq_desc *desc;
+	spin_lock(&resume_reason_lock);
+	for (irq_no = 0; irq_no < irq_count; irq_no++) {
+		desc = irq_to_desc(irq_list[irq_no]);
+		if (desc && desc->action && desc->action->name)
+			buf_offset += sprintf(buf + buf_offset, "%d %s\n",
+					irq_list[irq_no], desc->action->name);
+		else
+			buf_offset += sprintf(buf + buf_offset, "%d\n",
+					irq_list[irq_no]);
+	}
+	spin_unlock(&resume_reason_lock);
+	return buf_offset;
+}
+
+static struct kobj_attribute resume_reason = __ATTR(last_resume_reason, 0666,
+		reason_show, NULL);
+
+static struct attribute *attrs[] = {
+	&resume_reason.attr,
+	NULL,
+};
+static struct attribute_group attr_group = {
+	.attrs = attrs,
+};
+
+/*
+ * logs all the wake up reasons to the kernel
+ * stores the irqs to expose them to the userspace via sysfs
+ */
+void log_wakeup_reason(int irq)
+{
+	struct irq_desc *desc;
+	desc = irq_to_desc(irq);
+	if (desc && desc->action && desc->action->name)
+		printk(KERN_INFO "Resume caused by IRQ %d, %s\n", irq,
+				desc->action->name);
+	else
+		printk(KERN_INFO "Resume caused by IRQ %d\n", irq);
+
+	spin_lock(&resume_reason_lock);
+	irq_list[irq_count++] = irq;
+	spin_unlock(&resume_reason_lock);
+}
+
+/* Detects a suspend and clears all the previous wake up reasons*/
+static int wakeup_reason_pm_event(struct notifier_block *notifier,
+		unsigned long pm_event, void *unused)
+{
+	switch (pm_event) {
+	case PM_SUSPEND_PREPARE:
+		spin_lock(&resume_reason_lock);
+		irq_count = 0;
+		spin_unlock(&resume_reason_lock);
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block wakeup_reason_pm_notifier_block = {
+	.notifier_call = wakeup_reason_pm_event,
+};
+
+/* Initializes the sysfs parameter
+ * registers the pm_event notifier
+ */
+void __init wakeup_reason_init(void)
+{
+	int retval;
+	spin_lock_init(&resume_reason_lock);
+	retval = register_pm_notifier(&wakeup_reason_pm_notifier_block);
+	if (retval)
+		printk(KERN_WARNING "[%s] failed to register PM notifier %d\n",
+				__func__, retval);
+
+	wakeup_reason = kobject_create_and_add("wakeup_reasons", kernel_kobj);
+	if (!wakeup_reason) {
+		printk(KERN_WARNING "[%s] failed to create a sysfs kobject\n",
+				__func__);
+		return;
+	}
+	retval = sysfs_create_group(wakeup_reason, &attr_group);
+	if (retval) {
+		kobject_put(wakeup_reason);
+		printk(KERN_WARNING "[%s] failed to create a sysfs group %d\n",
+				__func__, retval);
+	}
+}
+
+late_initcall(wakeup_reason_init);