[RFC] thermal core: add option to run PM_POST_SUSPEND asynchronously

[RFC] thermal core: add option to run PM_POST_SUSPEND asynchronously

[Radu Solea]

Some thermal zones are bus connected and slow to resume, thus
delaying actions which depend on completion of PM_POST_SUSPEND.
Add optional execution path to resume thermal zones on the system
unbounded workqueue.

Signed-off-by: Radu Solea <radusolea@google.com>
---
 drivers/thermal/Kconfig        | 11 +++++++
 drivers/thermal/thermal_core.c | 58 ++++++++++++++++++++++++++++++----
 2 files changed, 62 insertions(+), 7 deletions(-)

diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index 19a4b33cb564..8dbcc62ccf8a 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -91,6 +91,17 @@ config THERMAL_WRITABLE_TRIPS
 	  Say 'Y' here if you would like to allow userspace tools to
 	  change trip temperatures.
 
+config THERMAL_ASYNC_RESUME
+	bool "Thermal async init zones on system resume"
+	default n
+	help
+	  Re-initialize thermal zones asynchronously on system resume.
+	  Thermal zone sensors may be attached on slow buses, impacting
+	  the duration of PM_POST_SUSPEND. If that is a concern enable
+	  this switch.
+
+	  If in doubt, say N.
+
 choice
 	prompt "Default Thermal governor"
 	default THERMAL_DEFAULT_GOV_STEP_WISE
diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 842f678c1c3e..5794832e4223 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -21,6 +21,10 @@
 #include <linux/of.h>
 #include <linux/suspend.h>
 
+#ifdef CONFIG_THERMAL_ASYNC_RESUME
+#include <linux/workqueue.h>
+#endif /* CONFIG_THERMAL_ASYNC_RESUME */
+
 #define CREATE_TRACE_POINTS
 #include "thermal_trace.h"
 
@@ -41,6 +45,10 @@ static atomic_t in_suspend;
 
 static struct thermal_governor *def_governor;
 
+#ifdef CONFIG_THERMAL_ASYNC_RESUME
+struct work_struct *resume_thermal_zones_wk;
+#endif /* CONFIG_THERMAL_ASYNC_RESUME */
+
 /*
  * Governor section: set of functions to handle thermal governors
  *
@@ -1495,26 +1503,53 @@ struct thermal_zone_device *thermal_zone_get_zone_by_name(const char *name)
 }
 EXPORT_SYMBOL_GPL(thermal_zone_get_zone_by_name);
 
-static int thermal_pm_notify(struct notifier_block *nb,
-			     unsigned long mode, void *_unused)
+static inline void resume_thermal_zones(void)
 {
 	struct thermal_zone_device *tz;
 
+	list_for_each_entry(tz, &thermal_tz_list, node) {
+		if (!thermal_zone_device_is_enabled(tz))
+			continue;
+
+		thermal_zone_device_init(tz);
+		thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
+	}
+}
+
+#ifdef CONFIG_THERMAL_ASYNC_RESUME
+static void thermal_resume_work_fn(struct work_struct *work)
+{
+	resume_thermal_zones();
+}
+
+static inline void thermal_resume_enqueue(void)
+{
+	INIT_WORK(resume_thermal_zones_wk, thermal_resume_work_fn);
+	queue_work(system_unbound_wq, resume_thermal_zones_wk);
+}
+#endif /* CONFIG_THERMAL_ASYNC_RESUME */
+
+static int thermal_pm_notify(struct notifier_block *nb,
+			     unsigned long mode, void *_unused)
+{
 	switch (mode) {
 	case PM_HIBERNATION_PREPARE:
 	case PM_RESTORE_PREPARE:
 	case PM_SUSPEND_PREPARE:
+#ifdef CONFIG_THERMAL_ASYNC_RESUME
+		flush_work(resume_thermal_zones_wk);
+#endif /* CONFIG_THERMAL_ASYNC_RESUME */
 		atomic_set(&in_suspend, 1);
 		break;
 	case PM_POST_HIBERNATION:
 	case PM_POST_RESTORE:
 	case PM_POST_SUSPEND:
 		atomic_set(&in_suspend, 0);
-		list_for_each_entry(tz, &thermal_tz_list, node) {
-			thermal_zone_device_init(tz);
-			thermal_zone_device_update(tz,
-						   THERMAL_EVENT_UNSPECIFIED);
-		}
+#ifdef CONFIG_THERMAL_ASYNC_RESUME
+		thermal_resume_enqueue();
+#else /* CONFIG_THERMAL_ASYNC_RESUME */
+		resume_thermal_zones();
+#endif /* CONFIG_THERMAL_ASYNC_RESUME */
 		break;
 	default:
 		break;
@@ -1530,6 +1565,15 @@ static int __init thermal_init(void)
 {
 	int result;
 
+#ifdef CONFIG_THERMAL_ASYNC_RESUME
+	resume_thermal_zones_wk = kmalloc(sizeof(*resume_thermal_zones_wk),
+					GFP_KERNEL);
+	if (!resume_thermal_zones_wk) {
+		result = -ENOMEM;
+		goto error;
+	}
+#endif /* CONFIG_THERMAL_ASYNC_RESUME */
+
 	result = thermal_netlink_init();
 	if (result)
 		goto error;
-- 
2.41.0.487.g6d72f3e995-goog