[RFC v4 1/5] PM: Add a sysfs file to represent the percentage of sleep in hardware 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 a new sysfs file
to represent the percentage of time spent in a sleep state.
This file will be present only if the system supports s2idle.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
RFC v3->v4
 * Switch to a percentage for reporting
 * Hook into timekeeping differently
---
 Documentation/ABI/testing/sysfs-power |  9 +++++++
 include/linux/suspend.h               |  2 ++
 include/linux/timekeeping.h           |  1 +
 kernel/power/main.c                   | 36 +++++++++++++++++++++++++++
 kernel/time/timekeeping.c             | 20 ++++++++++++---
 5 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index f99d433ff311..60b6948f5982 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -413,6 +413,15 @@ 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_percent
+Date:		December 2022
+Contact:	Mario Limonciello <mario.limonciello@amd.com>
+Description:
+		The /sys/power/suspend_stats/last_hw_sleep_percent file
+		contains the percentage of time that the last suspend cycle
+		was spent in a hardware sleep state.  It is expressed as an
+		integer between between 0 and 100.
+
 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..e0f2ac5f4406 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;
+	u64	last_hw_sleep;
 	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_set_hw_sleep_time(u64 t);
 
 #define pm_notifier(fn, pri) {				\
 	static struct notifier_block fn##_nb =			\
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index fe1e467ba046..2a81366f3e31 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -70,6 +70,7 @@ extern ktime_t ktime_get_coarse_with_offset(enum tk_offsets offs);
 extern ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs);
 extern ktime_t ktime_get_raw(void);
 extern u32 ktime_get_resolution_ns(void);
+extern u64 get_suspend_duration_ns(void);
 
 /**
  * ktime_get_real - get the real (wall-) time in ktime_t format
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 31ec4a9b9d70..be82f4a740c0 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 +84,12 @@ int unregister_pm_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL_GPL(unregister_pm_notifier);
 
+void pm_set_hw_sleep_time(u64 t)
+{
+	suspend_stats.last_hw_sleep = t;
+}
+EXPORT_SYMBOL_GPL(pm_set_hw_sleep_time);
+
 int pm_notifier_call_chain_robust(unsigned long val_up, unsigned long val_down)
 {
 	int ret;
@@ -377,6 +384,20 @@ 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_percent_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	u64 t = get_suspend_duration_ns();
+	int p;
+
+	if (!t)
+		return -EINVAL;
+
+	p = min((100 * NSEC_PER_USEC * suspend_stats.last_hw_sleep) / t, 100);
+	return sysfs_emit(buf, "%llu\n", p);
+}
+static struct kobj_attribute last_hw_sleep_percent = __ATTR_RO(last_hw_sleep_percent);
+
 static struct attribute *suspend_attrs[] = {
 	&success.attr,
 	&fail.attr,
@@ -391,12 +412,27 @@ static struct attribute *suspend_attrs[] = {
 	&last_failed_dev.attr,
 	&last_failed_errno.attr,
 	&last_failed_step.attr,
+	&last_hw_sleep_percent.attr,
 	NULL,
 };
 
+static umode_t suspend_attr_is_visible(struct kobject *kobj, struct attribute *attr, int idx)
+{
+	if (attr == &last_hw_sleep_percent.attr) {
+#ifdef CONFIG_ACPI
+		if (acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)
+			return 0444;
+#endif
+		return 0;
+	}
+
+	return 0444;
+}
+
 static const struct attribute_group suspend_attr_group = {
 	.name = "suspend_stats",
 	.attrs = suspend_attrs,
+	.is_visible = suspend_attr_is_visible,
 };
 
 #ifdef CONFIG_DEBUG_FS
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index f72b9f1de178..49119a942cb2 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1779,7 +1779,7 @@ void timekeeping_resume(void)
 	struct timekeeper *tk = &tk_core.timekeeper;
 	struct clocksource *clock = tk->tkr_mono.clock;
 	unsigned long flags;
-	struct timespec64 ts_new, ts_delta;
+	struct timespec64 ts_new;
 	u64 cycle_now, nsec;
 	bool inject_sleeptime = false;
 
@@ -1806,16 +1806,16 @@ void timekeeping_resume(void)
 	cycle_now = tk_clock_read(&tk->tkr_mono);
 	nsec = clocksource_stop_suspend_timing(clock, cycle_now);
 	if (nsec > 0) {
-		ts_delta = ns_to_timespec64(nsec);
+		timekeeping_suspend_time = ns_to_timespec64(nsec);
 		inject_sleeptime = true;
 	} else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) {
-		ts_delta = timespec64_sub(ts_new, timekeeping_suspend_time);
+		timekeeping_suspend_time = timespec64_sub(ts_new, timekeeping_suspend_time);
 		inject_sleeptime = true;
 	}
 
 	if (inject_sleeptime) {
 		suspend_timing_needed = false;
-		__timekeeping_inject_sleeptime(tk, &ts_delta);
+		__timekeeping_inject_sleeptime(tk, &timekeeping_suspend_time);
 	}
 
 	/* Re-base the last cycle value */
@@ -2232,6 +2232,18 @@ void update_wall_time(void)
 		clock_was_set_delayed();
 }
 
+/**
+ * get_suspend_duration_ns - Return the duration of a system suspend.
+ *
+ * Returns the calculation of the duration of time that passed while a
+ * system was suspended.
+ *
+ */
+u64 get_suspend_duration_ns(void)
+{
+	return timespec64_to_ns(&timekeeping_suspend_time);
+}
+
 /**
  * getboottime64 - Return the real time of system boot.
  * @ts:		pointer to the timespec64 to be set
-- 
2.34.1