Re: [PATCH v1] thermal: trip: Rework thermal_zone_set_trip() and its callers

From: Lukasz Luba
Date: Tue Nov 28 2023 - 03:17:16 EST

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In reply to: Rafael J. Wysocki: "[PATCH v1] thermal: trip: Rework thermal_zone_set_trip() and its callers"
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Hi Rafael,

On 11/27/23 19:59, Rafael J. Wysocki wrote:

From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

Both trip_point_temp_store() and trip_point_hyst_store() use
thermal_zone_set_trip() to update a given trip point, but none of them
actually needs to change more than one field in struct thermal_trip
representing it. However, each of them effectively calls
__thermal_zone_get_trip() twice in a row for the same trip index value,
once directly and once via thermal_zone_set_trip(), which is not
particularly efficient, and the way in which thermal_zone_set_trip()
carries out the update is not particularly straightforward.

Moreover, some checks done by them both need not go under the thermal
zone lock and code duplication between them can be reduced quilte a bit

s/quilte/quite/

by moving the majority of logic into thermal_zone_set_trip().

Rework all of the above funtcions to address the above.

s/funtcions/functions/

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---
drivers/thermal/thermal_core.h | 9 +++++
drivers/thermal/thermal_sysfs.c | 52 +++++++---------------------------
drivers/thermal/thermal_trip.c | 61 ++++++++++++++++++++++++++--------------
include/linux/thermal.h | 3 -
4 files changed, 61 insertions(+), 64 deletions(-)

Index: linux-pm/drivers/thermal/thermal_core.h
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_core.h
+++ linux-pm/drivers/thermal/thermal_core.h
@@ -122,6 +122,15 @@ void __thermal_zone_device_update(struct
void __thermal_zone_set_trips(struct thermal_zone_device *tz);
int __thermal_zone_get_trip(struct thermal_zone_device *tz, int trip_id,
struct thermal_trip *trip);
+
+enum thermal_set_trip_target {
+ THERMAL_TRIP_SET_TEMP,
+ THERMAL_TRIP_SET_HYST,
+};
+
+int thermal_zone_set_trip(struct thermal_zone_device *tz, int trip_id,
+ enum thermal_set_trip_target what, const char *buf);
+
int thermal_zone_trip_id(struct thermal_zone_device *tz,
const struct thermal_trip *trip);
int __thermal_zone_get_temp(struct thermal_zone_device *tz, int *temp);
Index: linux-pm/drivers/thermal/thermal_sysfs.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_sysfs.c
+++ linux-pm/drivers/thermal/thermal_sysfs.c
@@ -120,31 +120,17 @@ trip_point_temp_store(struct device *dev
const char *buf, size_t count)
{
struct thermal_zone_device *tz = to_thermal_zone(dev);
- struct thermal_trip trip;
- int trip_id, ret;
+ int trip_id;
+ int ret;
+
+ if (!device_is_registered(dev))
+ return -ENODEV;
if (sscanf(attr->attr.name, "trip_point_%d_temp", &trip_id) != 1)
return -EINVAL;
- mutex_lock(&tz->lock);
-
- if (!device_is_registered(dev)) {
- ret = -ENODEV;
- goto unlock;
- }
-
- ret = __thermal_zone_get_trip(tz, trip_id, &trip);
- if (ret)
- goto unlock;
-
- ret = kstrtoint(buf, 10, &trip.temperature);
- if (ret)
- goto unlock;
+ ret = thermal_zone_set_trip(tz, trip_id, THERMAL_TRIP_SET_TEMP, buf);
- ret = thermal_zone_set_trip(tz, trip_id, &trip);
-unlock:
- mutex_unlock(&tz->lock);
-
return ret ? ret : count;
}
@@ -179,30 +165,16 @@ trip_point_hyst_store(struct device *dev
const char *buf, size_t count)
{
struct thermal_zone_device *tz = to_thermal_zone(dev);
- struct thermal_trip trip;
- int trip_id, ret;
+ int trip_id;
+ int ret;
+
+ if (!device_is_registered(dev))
+ return -ENODEV;
if (sscanf(attr->attr.name, "trip_point_%d_hyst", &trip_id) != 1)
return -EINVAL;
- mutex_lock(&tz->lock);
-
- if (!device_is_registered(dev)) {
- ret = -ENODEV;
- goto unlock;
- }
-
- ret = __thermal_zone_get_trip(tz, trip_id, &trip);
- if (ret)
- goto unlock;
-
- ret = kstrtoint(buf, 10, &trip.hysteresis);
- if (ret)
- goto unlock;
-
- ret = thermal_zone_set_trip(tz, trip_id, &trip);
-unlock:
- mutex_unlock(&tz->lock);
+ ret = thermal_zone_set_trip(tz, trip_id, THERMAL_TRIP_SET_HYST, buf);
return ret ? ret : count;
}
Index: linux-pm/drivers/thermal/thermal_trip.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_trip.c
+++ linux-pm/drivers/thermal/thermal_trip.c
@@ -148,42 +148,61 @@ int thermal_zone_get_trip(struct thermal
EXPORT_SYMBOL_GPL(thermal_zone_get_trip);
int thermal_zone_set_trip(struct thermal_zone_device *tz, int trip_id,
- const struct thermal_trip *trip)
+ enum thermal_set_trip_target what, const char *buf)
{
- struct thermal_trip t;
- int ret;
+ struct thermal_trip *trip;
+ int val, ret = 0;
- if (!tz->ops->set_trip_temp && !tz->ops->set_trip_hyst && !tz->trips)
- return -EINVAL;

Here we could bail out when there are no callbacks.

+ if (trip_id < 0 || trip_id >= tz->num_trips)
+ ret = -EINVAL;
- ret = __thermal_zone_get_trip(tz, trip_id, &t);
+ ret = kstrtoint(buf, 10, &val);
if (ret)
return ret;
- if (t.type != trip->type)
- return -EINVAL;
+ mutex_lock(&tz->lock);
- if (t.temperature != trip->temperature && tz->ops->set_trip_temp) {
- ret = tz->ops->set_trip_temp(tz, trip_id, trip->temperature);
- if (ret)
- return ret;
- }
+ trip = &tz->trips[trip_id];
- if (t.hysteresis != trip->hysteresis && tz->ops->set_trip_hyst) {
- ret = tz->ops->set_trip_hyst(tz, trip_id, trip->hysteresis);
- if (ret)
- return ret;
+ switch (what) {
+ case THERMAL_TRIP_SET_TEMP:
+ if (val == trip->temperature)
+ goto unlock;
+
+ if (tz->ops->set_trip_temp) {
+ ret = tz->ops->set_trip_temp(tz, trip_id, val);
+ if (ret)
+ goto unlock;
+ }

But here we don't bail out and go line below

+ trip->temperature = val;

where we modify the actual '&tz->trips[trip_id]'.

Shouldn't be something like the code flow below?
--------------------------------------------8<-----------------------------
if (!tz->ops->set_trip_temp)
goto unlock;

ret = tz->ops->set_trip_temp(tz, trip_id, val);
if (ret)
goto unlock;

trip->temperature = val;
break
----------------------------------->8--------------------------------------

+ break;
+
+ case THERMAL_TRIP_SET_HYST:
+ if (val == trip->hysteresis)
+ goto unlock;
+
+ if (tz->ops->set_trip_hyst) {
+ ret = tz->ops->set_trip_hyst(tz, trip_id, val);
+ if (ret)
+ goto unlock;
+ }
+ trip->hysteresis = val;