power: Add option to log time spent in suspend

Prints the time spent in suspend in the kernel log, and
keeps statistics on the time spent in suspend in
/sys/kernel/debug/suspend_time

Change-Id: Ia6b9ebe4baa0f7f5cd211c6a4f7e813aefd3fa1d
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Todd Poynor <toddpoynor@google.com>

kernel/power/Kconfig

@@ -243,3 +243,10 @@ config PM_GENERIC_DOMAINS_RUNTIME
 config CPU_PM
 	bool
 	depends on SUSPEND || CPU_IDLE
+
+config SUSPEND_TIME
+	bool "Log time spent in suspend"
+	---help---
+	  Prints the time spent in suspend in the kernel log, and
+	  keeps statistics on the time spent in suspend in
+	  /sys/kernel/debug/suspend_time

kernel/power/Makefile

@@ -9,5 +9,6 @@ obj-$(CONFIG_SUSPEND)		+= suspend.o
 obj-$(CONFIG_PM_TEST_SUSPEND)	+= suspend_test.o
 obj-$(CONFIG_HIBERNATION)	+= hibernate.o snapshot.o swap.o user.o \
 				   block_io.o
+obj-$(CONFIG_SUSPEND_TIME)	+= suspend_time.o
 
 obj-$(CONFIG_MAGIC_SYSRQ)	+= poweroff.o

kernel/power/suspend_time.c

@@ -0,0 +1,111 @@
+/*
+ * debugfs file to track time spent in suspend
+ *
+ * Copyright (c) 2011, Google, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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/debugfs.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/seq_file.h>
+#include <linux/syscore_ops.h>
+#include <linux/time.h>
+
+static struct timespec suspend_time_before;
+static unsigned int time_in_suspend_bins[32];
+
+#ifdef CONFIG_DEBUG_FS
+static int suspend_time_debug_show(struct seq_file *s, void *data)
+{
+	int bin;
+	seq_printf(s, "time (secs)  count\n");
+	seq_printf(s, "------------------\n");
+	for (bin = 0; bin < 32; bin++) {
+		if (time_in_suspend_bins[bin] == 0)
+			continue;
+		seq_printf(s, "%4d - %4d %4u\n",
+			bin ? 1 << (bin - 1) : 0, 1 << bin,
+				time_in_suspend_bins[bin]);
+	}
+	return 0;
+}
+
+static int suspend_time_debug_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, suspend_time_debug_show, NULL);
+}
+
+static const struct file_operations suspend_time_debug_fops = {
+	.open		= suspend_time_debug_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+static int __init suspend_time_debug_init(void)
+{
+	struct dentry *d;
+
+	d = debugfs_create_file("suspend_time", 0755, NULL, NULL,
+		&suspend_time_debug_fops);
+	if (!d) {
+		pr_err("Failed to create suspend_time debug file\n");
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+late_initcall(suspend_time_debug_init);
+#endif
+
+static int suspend_time_syscore_suspend(void)
+{
+	read_persistent_clock(&suspend_time_before);
+
+	return 0;
+}
+
+static void suspend_time_syscore_resume(void)
+{
+	struct timespec after;
+
+	read_persistent_clock(&after);
+
+	after = timespec_sub(after, suspend_time_before);
+
+	time_in_suspend_bins[fls(after.tv_sec)]++;
+
+	pr_info("Suspended for %lu.%03lu seconds\n", after.tv_sec,
+		after.tv_nsec / NSEC_PER_MSEC);
+}
+
+static struct syscore_ops suspend_time_syscore_ops = {
+	.suspend = suspend_time_syscore_suspend,
+	.resume = suspend_time_syscore_resume,
+};
+
+static int suspend_time_syscore_init(void)
+{
+	register_syscore_ops(&suspend_time_syscore_ops);
+
+	return 0;
+}
+
+static void suspend_time_syscore_exit(void)
+{
+	unregister_syscore_ops(&suspend_time_syscore_ops);
+}
+module_init(suspend_time_syscore_init);
+module_exit(suspend_time_syscore_exit);