linux-kernel - [RFC PATCH] thermal: power_allocator: Ignore cutoff when integral is less than zero

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Message-ID: <20260119015803.183-1-xuewen.yan@unisoc.com>
Date: Mon, 19 Jan 2026 09:58:03 +0800
From: Xuewen Yan <xuewen.yan@...soc.com>
To: <lukasz.luba@....com>, <rafael@...nel.org>, <daniel.lezcano@...aro.org>,
        <rui.zhang@...el.com>
CC: <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <ke.wang@...soc.com>, <jeson.gao@...soc.com>, <di.shen@...soc.com>,
        <xuewen.yan94@...il.com>
Subject: [RFC PATCH] thermal: power_allocator: Ignore cutoff when integral is less than zero

From: Jeson Gao <jeson.gao@...soc.com>

The cutoff means threshold below which the error is no longer accumulated.
However, in some scenarios, this may cause performance degradation.

For example:
the control-temp is 85, the cutoff is 0 or other small value:

If the current temperature frequently exceeds the set temperature,
the negative integral will continuously accumulate.
Over an extended period, this will result in a significantly
large negative integral value, the positive integral can’t build up
because of the cutoff. This makes the power_range very low,
even if the temperature is already under the control target.

So, if the err_integral is negative, ignore the cutoff to force
add the positive integral.

Co-developed-by: Di Shen <di.shen@...soc.com>
Signed-off-by: Di Shen <di.shen@...soc.com>
Signed-off-by: Jeson Gao <jeson.gao@...soc.com>
Signed-off-by: Xuewen Yan <xuewen.yan@...soc.com>
---
 drivers/thermal/gov_power_allocator.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
index 0d9f636c80f4..404ae1d75612 100644
--- a/drivers/thermal/gov_power_allocator.c
+++ b/drivers/thermal/gov_power_allocator.c
@@ -263,7 +263,8 @@ static u32 pid_controller(struct thermal_zone_device *tz,
 	 */
 	i = mul_frac(tz->tzp->k_i, params->err_integral);

-	if (err < int_to_frac(tz->tzp->integral_cutoff)) {
+	if (err < int_to_frac(tz->tzp->integral_cutoff) ||
+	    (err > 0 && params->err_integral < 0)) {
 		s64 i_next = i + mul_frac(tz->tzp->k_i, err);

 		if (abs(i_next) < max_power_frac) {
-- 
2.25.1