[PATCH v6 1/4] PM: Add sysfs files to represent time spent in hardware sleep state

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

Userspace can't easily discover how much of a sleep cycle was spent in a
hardware sleep state without using kernel tracing and vendor specific sysfs
or debugfs files.

To make this information more discoverable, introduce two new sysfs files:
1) The time spent in a hw sleep state for last cycle.
2) The time spent in a hw sleep state since the kernel booted
Both of these files will be present only if the system supports s2idle.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
v5->v6:
 * Add total attribute as well
 * Change text for documentation
 * Adjust flow of is_visible callback.
 * If overflow was detected in total attribute return -EOVERFLOW
 * Rename symbol
 * Add stub for symbol for builds without CONFIG_PM_SLEEP
v4->v5:
 * Provide time in microseconds instead of percent. Userspace can convert
   this if desirable.
---
 Documentation/ABI/testing/sysfs-power | 27 ++++++++++++++++
 include/linux/suspend.h               |  5 +++
 kernel/power/main.c                   | 45 +++++++++++++++++++++++++++
 3 files changed, 77 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index f99d433ff311..37240575d282 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -413,6 +413,33 @@ 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_hw_sleep
+Date:		June 2023
+Contact:	Mario Limonciello <mario.limonciello@amd.com>
+Description:
+		The /sys/power/suspend_stats/last_hw_sleep file
+		contains the duration of time spent in a hardware sleep
+		state in the most recent system suspend-resume cycle.
+		This number is measured in microseconds.
+
+		NOTE: Limitations in the size of the hardware counters may
+		cause this value to be inaccurate in longer sleep cycles.
+
+What:		/sys/power/suspend_stats/total_hw_sleep
+Date:		June 2023
+Contact:	Mario Limonciello <mario.limonciello@amd.com>
+Description:
+		The /sys/power/suspend_stats/total_hw_sleep file
+		contains the aggregate of time spent in a hardware sleep
+		state since the kernel was booted. This number
+		is measured in microseconds.
+
+		NOTE: Limitations in the size of the hardware counters may
+		cause this value to be inaccurate in longer sleep cycles.
+
+		If an overflow has been detected this file will return
+		-EOVERFLOW.
+
 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..069ef0c0ae57 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -68,6 +68,8 @@ struct suspend_stats {
 	int	last_failed_errno;
 	int	errno[REC_FAILED_NUM];
 	int	last_failed_step;
+	u64	last_hw_sleep;
+	u64	total_hw_sleep;
 	enum suspend_stat_step	failed_steps[REC_FAILED_NUM];
 };
 
@@ -489,6 +491,7 @@ 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_report_hw_sleep_time(u64 t);
 
 #define pm_notifier(fn, pri) {				\
 	static struct notifier_block fn##_nb =			\
@@ -526,6 +529,8 @@ static inline int unregister_pm_notifier(struct notifier_block *nb)
 	return 0;
 }
 
+static inline void pm_report_hw_sleep_time(u64 t) {};
+
 static inline void ksys_sync_helper(void) {}
 
 #define pm_notifier(fn, pri)	do { (void)(fn); } while (0)
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 31ec4a9b9d70..ffd4dd43cbdd 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>
@@ -83,6 +84,18 @@ int unregister_pm_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL_GPL(unregister_pm_notifier);
 
+void pm_report_hw_sleep_time(u64 t)
+{
+	suspend_stats.last_hw_sleep = t;
+	if (suspend_stats.total_hw_sleep == -EOVERFLOW)
+		return;
+	if (suspend_stats.total_hw_sleep + t < suspend_stats.total_hw_sleep)
+		suspend_stats.total_hw_sleep = -EOVERFLOW;
+	else
+		suspend_stats.total_hw_sleep += t;
+}
+EXPORT_SYMBOL_GPL(pm_report_hw_sleep_time);
+
 int pm_notifier_call_chain_robust(unsigned long val_up, unsigned long val_down)
 {
 	int ret;
@@ -377,6 +390,22 @@ 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_hw_sleep_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%llu\n", suspend_stats.last_hw_sleep);
+}
+static struct kobj_attribute last_hw_sleep = __ATTR_RO(last_hw_sleep);
+
+static ssize_t total_hw_sleep_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	if (suspend_stats.total_hw_sleep == -EOVERFLOW)
+		return suspend_stats.total_hw_sleep;
+	return sysfs_emit(buf, "%llu\n", suspend_stats.total_hw_sleep);
+}
+static struct kobj_attribute total_hw_sleep = __ATTR_RO(total_hw_sleep);
+
 static struct attribute *suspend_attrs[] = {
 	&success.attr,
 	&fail.attr,
@@ -391,12 +420,28 @@ static struct attribute *suspend_attrs[] = {
 	&last_failed_dev.attr,
 	&last_failed_errno.attr,
 	&last_failed_step.attr,
+	&last_hw_sleep.attr,
+	&total_hw_sleep.attr,
 	NULL,
 };
 
+static umode_t suspend_attr_is_visible(struct kobject *kobj, struct attribute *attr, int idx)
+{
+	if (attr != &last_hw_sleep.attr &&
+	    attr != &total_hw_sleep.attr)
+		return 0444;
+
+#ifdef CONFIG_ACPI
+	if (acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)
+		return 0444;
+#endif
+	return 0;
+}
+
 static const struct attribute_group suspend_attr_group = {
 	.name = "suspend_stats",
 	.attrs = suspend_attrs,
+	.is_visible = suspend_attr_is_visible,
 };
 
 #ifdef CONFIG_DEBUG_FS
-- 
2.34.1