[RFC v3 1/4] PM: Add a sysfs file to represent the total sleep duration

[Mario Limonciello <mario.limonciello@amd.com>]

For userspace to be able to analyze how much of a suspend cycle was spent
in the hardware sleep states userspace software has to use kernel trace
points paired with the file `low_power_idle_system_residency_us` on
supported systems.

To make this information more discoverable, introduce a new sysfs file
to represent the duration spent in a sleep state.
This file will be present and updated during resume for all suspend
types.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
RFC v2->v3
 * Drop one of the sysfs files
 * Use sysfs_emit instead
 * Fix symbol name (s/type/time/)
 * Drop is_visible
 * Use timespec64 type for suspend stats
 * Update documentation
 * Update sysfs file name
---
 Documentation/ABI/testing/sysfs-power |  8 ++++++++
 include/linux/suspend.h               |  2 ++
 kernel/power/main.c                   | 15 +++++++++++++++
 kernel/power/suspend.c                |  2 ++
 kernel/time/timekeeping.c             |  2 ++
 5 files changed, 29 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index f99d433ff311..3abe20c47e08 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -413,6 +413,14 @@ Description:
 		The /sys/power/suspend_stats/last_failed_step file contains
 		the last failed step in the suspend/resume path.
 
+What:		/sys/power/suspend_stats/last_total
+Date:		December 2022
+Contact:	Mario Limonciello <mario.limonciello@amd.com>
+Description:
+		The /sys/power/suspend_stats/last_total file contains
+		the total duration of the sleep cycle.
+		This is measured in microseconds.
+
 What:		/sys/power/sync_on_suspend
 Date:		October 2019
 Contact:	Jonas Meurer <jonas@freesources.org>
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index cfe19a028918..57f29ab4176c 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -68,6 +68,7 @@ struct suspend_stats {
 	int	last_failed_errno;
 	int	errno[REC_FAILED_NUM];
 	int	last_failed_step;
+	struct timespec64	last_total;
 	enum suspend_stat_step	failed_steps[REC_FAILED_NUM];
 };
 
@@ -489,6 +490,7 @@ void restore_processor_state(void);
 extern int register_pm_notifier(struct notifier_block *nb);
 extern int unregister_pm_notifier(struct notifier_block *nb);
 extern void ksys_sync_helper(void);
+extern void pm_account_suspend_time(const struct timespec64 t);
 
 #define pm_notifier(fn, pri) {				\
 	static struct notifier_block fn##_nb =			\
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 31ec4a9b9d70..f33012860699 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -6,6 +6,7 @@
  * Copyright (c) 2003 Open Source Development Lab
  */
 
+#include <linux/acpi.h>
 #include <linux/export.h>
 #include <linux/kobject.h>
 #include <linux/string.h>
@@ -54,6 +55,11 @@ void unlock_system_sleep(unsigned int flags)
 }
 EXPORT_SYMBOL_GPL(unlock_system_sleep);
 
+void pm_account_suspend_time(const struct timespec64 t)
+{
+	suspend_stats.last_total = timespec64_add(suspend_stats.last_total, t);
+}
+
 void ksys_sync_helper(void)
 {
 	ktime_t start;
@@ -377,6 +383,14 @@ static ssize_t last_failed_step_show(struct kobject *kobj,
 }
 static struct kobj_attribute last_failed_step = __ATTR_RO(last_failed_step);
 
+static ssize_t last_total_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%llu\n",
+			  timespec64_to_ns(&suspend_stats.last_total) / NSEC_PER_USEC);
+}
+static struct kobj_attribute last_total = __ATTR_RO(last_total);
+
 static struct attribute *suspend_attrs[] = {
 	&success.attr,
 	&fail.attr,
@@ -391,6 +405,7 @@ static struct attribute *suspend_attrs[] = {
 	&last_failed_dev.attr,
 	&last_failed_errno.attr,
 	&last_failed_step.attr,
+	&last_total.attr,
 	NULL,
 };
 
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index fa3bf161d13f..cb0f72f52528 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -423,6 +423,8 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
 	if (suspend_test(TEST_PLATFORM))
 		goto Platform_wake;
 
+	suspend_stats.last_total = (struct timespec64) { 0, 0 };
+
 	if (state == PM_SUSPEND_TO_IDLE) {
 		s2idle_loop();
 		goto Platform_wake;
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index f72b9f1de178..f9c8cfef8fc5 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -24,6 +24,7 @@
 #include <linux/compiler.h>
 #include <linux/audit.h>
 #include <linux/random.h>
+#include <linux/suspend.h>
 
 #include "tick-internal.h"
 #include "ntp_internal.h"
@@ -1698,6 +1699,7 @@ static void __timekeeping_inject_sleeptime(struct timekeeper *tk,
 	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *delta));
 	tk_update_sleep_time(tk, timespec64_to_ktime(*delta));
 	tk_debug_account_sleep_time(delta);
+	pm_account_suspend_time(*delta);
 }
 
 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
-- 
2.34.1