[PATCH v2 2/5] PM: runtime: Convert last_busy to atomic64_t

[Brian Norris]

I want to use the atomic64 compare/exchange helpers. There are no
similar 32-bit-portable helpers for non-atomic64_t.

As a side effect, this also should avoid some minor load/store tearing
corner cases on 32-bit architectures.

Signed-off-by: Brian Norris <briannorris at chromium.org>
---

Changes in v2:
 * Add <linux/atomic.h> to pm_runtime.h too

 drivers/base/power/runtime.c | 4 +++-
 include/linux/pm.h           | 3 ++-
 include/linux/pm_runtime.h   | 3 ++-
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 9d3508d9b4a2..2a117d6a776f 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -5,6 +5,8 @@
  * Copyright (c) 2009 Rafael J. Wysocki <rjw at sisk.pl>, Novell Inc.
  * Copyright (C) 2010 Alan Stern <stern at rowland.harvard.edu>
  */
+
+#include <linux/atomic.h>
 #include <linux/sched/mm.h>
 #include <linux/ktime.h>
 #include <linux/hrtimer.h>
@@ -186,7 +188,7 @@ u64 pm_runtime_autosuspend_expiration(struct device *dev)
 	if (autosuspend_delay < 0)
 		return 0;
 
-	expires  = READ_ONCE(dev->power.last_busy);
+	expires = atomic64_read(&dev->power.last_busy);
 	expires += (u64)autosuspend_delay * NSEC_PER_MSEC;
 	if (expires > ktime_get_mono_fast_ns())
 		return expires;	/* Expires in the future */
diff --git a/include/linux/pm.h b/include/linux/pm.h
index ef3f1310e749..531e46ff878e 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -8,6 +8,7 @@
 #ifndef _LINUX_PM_H
 #define _LINUX_PM_H
 
+#include <linux/atomic.h>
 #include <linux/completion.h>
 #include <linux/export.h>
 #include <linux/hrtimer_types.h>
@@ -812,7 +813,7 @@ struct dev_pm_info {
 	enum rpm_status		last_status;
 	int			runtime_error;
 	int			autosuspend_delay;
-	u64			last_busy;
+	atomic64_t		last_busy;
 	u64			active_time;
 	u64			suspended_time;
 	u64			accounting_timestamp;
diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
index ae68a9dc7fc5..da537be94732 100644
--- a/include/linux/pm_runtime.h
+++ b/include/linux/pm_runtime.h
@@ -8,6 +8,7 @@
 #ifndef _LINUX_PM_RUNTIME_H
 #define _LINUX_PM_RUNTIME_H
 
+#include <linux/atomic.h>
 #include <linux/device.h>
 #include <linux/notifier.h>
 #include <linux/pm.h>
@@ -242,7 +243,7 @@ static inline bool pm_runtime_has_no_callbacks(struct device *dev)
  */
 static inline void pm_runtime_mark_last_busy(struct device *dev)
 {
-	WRITE_ONCE(dev->power.last_busy, ktime_get_mono_fast_ns());
+	atomic64_set(&dev->power.last_busy, ktime_get_mono_fast_ns());
 }
 
 /**
-- 
2.56.0.398.g882cbad275-goog