[PATCH v4 1/3] thermal: create a helper __thermal_cdev_update() without a lock

From: Lukasz Luba
Date: Thu Apr 22 2021 - 07:43:24 EST


There is a need to have a helper function which updates cooling device
state from the governors code. With this change governor can use
lock and unlock while calling helper function. This avoid unnecessary
second time lock/unlock which was in previous solution present in
governor implementation. This new helper function must be called
with mutex 'cdev->lock' hold.

The changed been discussed and part of code presented in thread:
https://lore.kernel.org/linux-pm/20210419084536.25000-1-lukasz.luba@xxxxxxx/

Co-developed-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Signed-off-by: Lukasz Luba <lukasz.luba@xxxxxxx>
---
drivers/thermal/thermal_core.h | 1 +
drivers/thermal/thermal_helpers.c | 27 +++++++++++++++++----------
2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/drivers/thermal/thermal_core.h b/drivers/thermal/thermal_core.h
index 86b8cef7310e..726e327b4205 100644
--- a/drivers/thermal/thermal_core.h
+++ b/drivers/thermal/thermal_core.h
@@ -66,6 +66,7 @@ static inline bool cdev_is_power_actor(struct thermal_cooling_device *cdev)
}

void thermal_cdev_update(struct thermal_cooling_device *);
+void __thermal_cdev_update(struct thermal_cooling_device *cdev);

/**
* struct thermal_trip - representation of a point in temperature domain
diff --git a/drivers/thermal/thermal_helpers.c b/drivers/thermal/thermal_helpers.c
index 7f50f412e02a..3edd047e144f 100644
--- a/drivers/thermal/thermal_helpers.c
+++ b/drivers/thermal/thermal_helpers.c
@@ -192,18 +192,11 @@ static void thermal_cdev_set_cur_state(struct thermal_cooling_device *cdev,
thermal_cooling_device_stats_update(cdev, target);
}

-void thermal_cdev_update(struct thermal_cooling_device *cdev)
+void __thermal_cdev_update(struct thermal_cooling_device *cdev)
{
struct thermal_instance *instance;
unsigned long target = 0;

- mutex_lock(&cdev->lock);
- /* cooling device is updated*/
- if (cdev->updated) {
- mutex_unlock(&cdev->lock);
- return;
- }
-
/* Make sure cdev enters the deepest cooling state */
list_for_each_entry(instance, &cdev->thermal_instances, cdev_node) {
dev_dbg(&cdev->device, "zone%d->target=%lu\n",
@@ -216,11 +209,25 @@ void thermal_cdev_update(struct thermal_cooling_device *cdev)

thermal_cdev_set_cur_state(cdev, target);

- cdev->updated = true;
- mutex_unlock(&cdev->lock);
trace_cdev_update(cdev, target);
dev_dbg(&cdev->device, "set to state %lu\n", target);
}
+
+/**
+ * thermal_cdev_update - update cooling device state if needed
+ * @cdev: pointer to struct thermal_cooling_device
+ *
+ * Update the cooling device state if there is a need.
+ */
+void thermal_cdev_update(struct thermal_cooling_device *cdev)
+{
+ mutex_lock(&cdev->lock);
+ if (!cdev->updated) {
+ __thermal_cdev_update(cdev);
+ cdev->updated = true;
+ }
+ mutex_unlock(&cdev->lock);
+}
EXPORT_SYMBOL(thermal_cdev_update);

/**
--
2.17.1