linux-kernel - Re: [PATCH v3 4/7] thermal/drivers/tegra: Add driver for Tegra30 thermal sensor

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Date:   Tue, 15 Jun 2021 12:03:28 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Amit Kucheria <amitk@...nel.org>,
        Andreas Westman Dorcsak <hedmoo@...oo.com>,
        Maxim Schwalm <maxim.schwalm@...il.com>,
        Svyatoslav Ryhel <clamor95@...il.com>,
        Ihor Didenko <tailormoon@...bler.ru>,
        Ion Agorria <ion@...rria.com>,
        Matt Merhar <mattmerhar@...tonmail.com>,
        Peter Geis <pgwipeout@...il.com>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-pm@...r.kernel.org,
        Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH v3 4/7] thermal/drivers/tegra: Add driver for Tegra30
 thermal sensor


[Cc Viresh]

On 29/05/2021 19:09, Dmitry Osipenko wrote:
> All NVIDIA Tegra30 SoCs have a two-channel on-chip sensor unit which
> monitors temperature and voltage of the SoC. Sensors control CPU frequency
> throttling, which is activated by hardware once preprogrammed temperature
> level is breached, they also send signal to Power Management controller to
> perform emergency shutdown on a critical overheat of the SoC die. Add
> driver for the Tegra30 TSENSOR module, exposing it as a thermal sensor
> and a cooling device.

IMO it does not make sense to expose the hardware throttling mechanism
as a cooling device because it is not usable anywhere from the thermal
framework.

Moreover, that will collide with the thermal / cpufreq framework
mitigation (hardware sets the frequency but the software thinks the freq
is different), right ?

The hardware limiter should let know the cpufreq framework about the
frequency change.

	https://lkml.org/lkml/2021/6/8/1792

May be post the sensor without the hw limiter for now and address that
in a separate series ?

  -- Daniel

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