[PATCH v2] power: add an API to log wakeup reasons

[PATCH v2] power: add an API to log wakeup reasons

[Ruchi Kandoi]

Add API log_wakeup_reason() and expose it to userspace via sysfs path
/sys/kernel/wakeup_reasons/last_resume_reason
This is useful for power management diagnostic purposes.

Signed-off-by: Ruchi Kandoi <kandoiruchi@google.com>
Signed-off-by: Greg Hackmann <ghackmann@google.com>
---
printk changed to pr_warn/pr_info
added pr_fmt(fmt) "wakeup_reason:" fmt
guard condition for MAX_WAKEUP_REASON_IRQ changed from == to >=
---
 include/linux/wakeup_reason.h |  23 +++++++
 kernel/power/Makefile         |   2 +-
 kernel/power/wakeup_reason.c  | 141 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 165 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/wakeup_reason.h
 create mode 100644 kernel/power/wakeup_reason.c

diff --git a/include/linux/wakeup_reason.h b/include/linux/wakeup_reason.h
new file mode 100644
index 0000000..7ce50f0
--- /dev/null
+++ b/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 */
diff --git a/kernel/power/Makefile b/kernel/power/Makefile
index 29472bf..f98f021 100644
--- a/kernel/power/Makefile
+++ b/kernel/power/Makefile
@@ -5,7 +5,7 @@ obj-y				+= qos.o
 obj-$(CONFIG_PM)		+= main.o
 obj-$(CONFIG_VT_CONSOLE_SLEEP)	+= console.o
 obj-$(CONFIG_FREEZER)		+= process.o
-obj-$(CONFIG_SUSPEND)		+= suspend.o
+obj-$(CONFIG_SUSPEND)		+= suspend.o wakeup_reason.o
 obj-$(CONFIG_PM_TEST_SUSPEND)	+= suspend_test.o
 obj-$(CONFIG_HIBERNATION)	+= hibernate.o snapshot.o swap.o user.o \
 				   block_io.o
diff --git a/kernel/power/wakeup_reason.c b/kernel/power/wakeup_reason.c
new file mode 100644
index 0000000..a21c592
--- /dev/null
+++ b/kernel/power/wakeup_reason.c
@@ -0,0 +1,141 @@
+/*
+ * 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.
+ */
+#define pr_fmt(fmt) "wakeup_reason:" fmt
+
+#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 irqcount;
+static struct kobject *wakeup_reason;
+static spinlock_t resume_reason_lock;
+
+static ssize_t reason_show(struct kobject *kobj, struct kobj_attribute *attr,
+		char *buf)
+{
+	int irq_no, buf_offset = 0;
+	struct irq_desc *desc;
+	spin_lock(&resume_reason_lock);
+	for (irq_no = 0; irq_no < irqcount; 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)
+		pr_info("Resume caused by IRQ %d, %s\n", irq,
+				desc->action->name);
+	else
+		pr_info("Resume caused by IRQ %d\n", irq);
+
+	spin_lock(&resume_reason_lock);
+	if (irqcount >= MAX_WAKEUP_REASON_IRQS) {
+		spin_unlock(&resume_reason_lock);
+		pr_warn("Resume caused by more than %d IRQs\n",
+				MAX_WAKEUP_REASON_IRQS);
+		return;
+	}
+
+	irq_list[irqcount++] = 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);
+		irqcount = 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
+ */
+int __init wakeup_reason_init(void)
+{
+	int retval;
+	spin_lock_init(&resume_reason_lock);
+	retval = register_pm_notifier(&wakeup_reason_pm_notifier_block);
+	if (retval)
+		pr_warn("%s: failed to register PM notifier %d\n",
+				__func__, retval);
+
+	wakeup_reason = kobject_create_and_add("wakeup_reasons", kernel_kobj);
+	if (!wakeup_reason) {
+		pr_warn("%s: failed to create a sysfs kobject\n",
+				__func__);
+		return 1;
+	}
+	retval = sysfs_create_group(wakeup_reason, &attr_group);
+	if (retval) {
+		kobject_put(wakeup_reason);
+		pr_warn("%s: failed to create a sysfs group %d\n",
+				__func__, retval);
+	}
+	return 0;
+}
+
+late_initcall(wakeup_reason_init);
-- 
1.9.0.279.gdc9e3eb

Re: [PATCH v2] power: add an API to log wakeup reasons

[John Stultz]

On 03/11/2014 07:02 PM, Ruchi Kandoi wrote:
> Add API log_wakeup_reason() and expose it to userspace via sysfs path
> /sys/kernel/wakeup_reasons/last_resume_reason
> This is useful for power management diagnostic purposes.

Thanks for re-submitting!

This commit message is still really too brief, focusing only on what
you're doing and not *why*. You should include some of the rational you
provided in in your earlier reply.

The following template is usually good to follow:

1) The Why: Explanation of a problem (and how it came to be) or
problematic use case to be overcome.

2) The What: Your approach or design to solving the problem, with
details on any tradeoffs, or particular benefits of your solution that
should be noted.

I know it can seem terribly verbose for small patches, but it helps
maintainers and other reviewers get into the right context in order to
understand what your patch does before they look at the code.

thanks
-john