linux-kernel - cpufreq/thermal regression in 6.10

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Date: Sun, 9 Jun 2024 09:53:20 +0200
From: Johan Hovold <johan@...nel.org>
To: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Viresh Kumar <viresh.kumar@...aro.org>, Zhang Rui <rui.zhang@...el.com>,
	Lukasz Luba <lukasz.luba@....com>,
	Steev Klimaszewski <steev@...i.org>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, regressions@...ts.linux.dev
Subject: cpufreq/thermal regression in 6.10

Hi,

Steev reported to me off-list that the CPU frequency of the big cores on
the Lenovo ThinkPad X13s sometimes appears to get stuck at a low
frequency with 6.10-rc2.

I just confirmed that once the cores are fully throttled (using the
stepwise thermal governor) due to the skin temperature reaching the
first trip point, scaling_max_freq gets stuck at the next OPP:

	cpu4/cpufreq/scaling_max_freq:940800
	cpu5/cpufreq/scaling_max_freq:940800
	cpu6/cpufreq/scaling_max_freq:940800
	cpu7/cpufreq/scaling_max_freq:940800

when the temperature drops again.

This obviously leads to a massive performance drop and could possibly
also be related to reports like this one:

	https://lore.kernel.org/all/CAHk-=wjwFGQZcDinK=BkEaA8FSyVg5NaUe0BobxowxeZ5PvetA@mail.gmail.com/

I assume the regression may have been introduced by all the thermal work
that went into 6.10-rc1, but I don't have time to try to track this down
myself right now (and will be away from keyboard most of next week).

I've confirmed that 6.9 works as expected.

Johan

#regzbot introduced: v6.9..v6.10-rc2