linux-kernel - Re: [PATCH v2] thermal: core: Add trip thresholds for trip crossing detection

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Message-ID: <3fe787bc-f85c-4268-833f-86922415c4d3@linaro.org>
Date:   Fri, 3 Nov 2023 17:30:26 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     srinivas pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Lukasz Luba <lukasz.luba@....com>
Subject: Re: [PATCH v2] thermal: core: Add trip thresholds for trip crossing
 detection

On 03/11/2023 16:42, srinivas pandruvada wrote:
> On Fri, 2023-11-03 at 15:56 +0100, Rafael J. Wysocki wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>
>> The trip crossing detection in handle_thermal_trip() does not work
>> correctly in the cases when a trip point is crossed on the way up and
>> then the zone temperature stays above its low temperature (that is,
>> its
>> temperature decreased by its hysteresis).  The trip temperature may
>> be passed by the zone temperature subsequently in that case, even
>> multiple times, but that does not count as the trip crossing as long
>> as
>> the zone temperature does not fall below the trip's low temperature
>> or,
>> in other words, until the trip is crossed on the way down.
> 
> In other words you want to avoid multiple trip UP notifications without
> a corresponding DOWN notification.
> 
> This will reduce unnecessary noise to user space. Is this the
> intention?

Not only reduce noise but give a correct information. Otherwise the 
userspace will have to figure out if there are duplicate events after 
the first event happened. The same happen (less often) when crossing the 
trip point the way down.



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