6.17-stable review patch. If anyone has any objections, please let me know.
------------------
From: Rafael J. Wysocki rafael.j.wysocki@intel.com
[ Upstream commit 2e82368359f63567862a0d438710ddffcb1ace83 ]
The current behavior of the Step-wise thermal governor is to increase the cooling level one step at a time after trip point threshold passing by thermal zone temperature until the temperature stops to rise. Then, nothing is done until the temperature decreases below the (possibly updated) trip point threshold, at which point the cooling level is reduced straight to the applicable minimum.
While this generally works, it is not in agreement with the throttling logic description comment in step_wise_manage() any more after some relatively recent changes, and in the case of passive cooling, it may lead to undesirable performance oscillations between high and low levels.
For this reason, modify the governor's cooling device state selection function, get_target_state(), to reduce cooling by one level even if the temperature is still above the thermal zone threshold, but the temperature has started to fall down. However, ensure that the cooling level will remain above the applicable minimum in that case to pull the zone temperature further down, possibly until it falls below the trip threshold (which may now be equal to the low temperature of the trip).
Doing so should help higher performance to be restored earlier in some cases which is desirable especially for passive trip points with relatively high hysteresis values.
Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Lukasz Luba lukasz.luba@arm.com Link: https://patch.msgid.link/1947735.tdWV9SEqCh@rafael.j.wysocki [ rjw: Changelog edits ] Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/thermal/gov_step_wise.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/drivers/thermal/gov_step_wise.c b/drivers/thermal/gov_step_wise.c index d1bb59f1dfbd3..b7938bddd9a6a 100644 --- a/drivers/thermal/gov_step_wise.c +++ b/drivers/thermal/gov_step_wise.c @@ -20,7 +20,9 @@ * If the temperature is higher than a trip point, * a. if the trend is THERMAL_TREND_RAISING, use higher cooling * state for this trip point - * b. if the trend is THERMAL_TREND_DROPPING, do nothing + * b. if the trend is THERMAL_TREND_DROPPING, use a lower cooling state + * for this trip point, but keep the cooling state above the applicable + * minimum * If the temperature is lower than a trip point, * a. if the trend is THERMAL_TREND_RAISING, do nothing * b. if the trend is THERMAL_TREND_DROPPING, use lower cooling @@ -51,6 +53,17 @@ static unsigned long get_target_state(struct thermal_instance *instance, if (throttle) { if (trend == THERMAL_TREND_RAISING) return clamp(cur_state + 1, instance->lower, instance->upper); + + /* + * If the zone temperature is falling, the cooling level can + * be reduced, but it should still be above the lower state of + * the given thermal instance to pull the temperature further + * down. + */ + if (trend == THERMAL_TREND_DROPPING) + return clamp(cur_state - 1, + min(instance->lower + 1, instance->upper), + instance->upper); } else if (trend == THERMAL_TREND_DROPPING) { if (cur_state <= instance->lower) return THERMAL_NO_TARGET;