linux-kernel - Re: [PATCH RESEND v2 3/5] thermal/drivers/mediatek/lvts: Disable low offset IRQ for minimum threshold

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Message-ID: <90dd8d93-5653-47f1-8435-f03502e4c0cc@linaro.org>
Date: Tue, 14 Jan 2025 19:30:31 +0100
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Nícolas F. R. A. Prado <nfraprado@...labora.com>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Zhang Rui <rui.zhang@...el.com>,
 Lukasz Luba <lukasz.luba@....com>, Matthias Brugger
 <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Alexandre Mergnat <amergnat@...libre.com>, Balsam CHIHI <bchihi@...libre.com>
Cc: kernel@...labora.com, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org, Hsin-Te Yuan <yuanhsinte@...omium.org>,
 Chen-Yu Tsai <wenst@...omium.org>, Bernhard Rosenkränzer
 <bero@...libre.com>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
 stable@...r.kernel.org
Subject: Re: [PATCH RESEND v2 3/5] thermal/drivers/mediatek/lvts: Disable low
 offset IRQ for minimum threshold

On 13/01/2025 14:27, Nícolas F. R. A. Prado wrote:
> In order to get working interrupts, a low offset value needs to be
> configured. The minimum value for it is 20 Celsius, which is what is
> configured when there's no lower thermal trip (ie the thermal core
> passes -INT_MAX as low trip temperature). However, when the temperature
> gets that low and fluctuates around that value it causes an interrupt
> storm.

Is it really about an irq storm or about having a temperature threshold 
set close to the ambiant temperature. So leading to unnecessary wakeups 
as there is need for mitigation ?

> Prevent that interrupt storm by not enabling the low offset interrupt if
> the low threshold is the minimum one.

The case where the high threshold is the INT_MAX should be handled too. 
The system may have configured a thermal zone without critical trip 
points, so setting the next upper threshold will program the register 
with INT_MAX. I guess it is an undefined behavior in this case, right ?

> Cc: stable@...r.kernel.org

[ ... ]

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