linux-kernel - Re: [PATCH 01/14] thermal: exynos: Reading temperature makes sense only when TMU is turned on

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Message-ID: <60958515.5KCaPvLZ9i@amdc3058>
Date:   Mon, 16 Apr 2018 14:17:44 +0200
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Eduardo Valentin <edubezval@...il.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kukjin Kim <kgene@...nel.org>,
        linux-samsung-soc@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH 01/14] thermal: exynos: Reading temperature makes sense
 only when TMU is turned on

On Monday, April 16, 2018 02:06:41 PM Daniel Lezcano wrote:
> On 16/04/2018 12:11, Bartlomiej Zolnierkiewicz wrote:
> > From: Marek Szyprowski <m.szyprowski@...sung.com>
> > 
> > When thermal sensor is not yet enabled, reading temperature might return
> > random value. This might even result in stopping system booting when such
> > temperature is higher than the critical value. Fix this by checking if TMU
> > has been actually enabled before reading the temperature.
> > 
> > This change fixes booting of Exynos4210-based board with TMU enabled (for
> > example Samsung Trats board), which was broken since v4.4 kernel release.
> 
> Why not move the thermal_zone_of_sensor_register *after* initializing
> the sensor ?

For initializing the sensor we need data obtained from
therm_zone_of_sensor_register() so it cannot be easily
done (especially since we also want the fix to be
ported to -stable kernels). For more detailed description
please see:

https://lkml.org/lkml/2018/4/10/376

> > Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> > Fixes: 9e4249b40340 ("thermal: exynos: Fix first temperature read after registering sensor")
> > CC: stable@...r.kernel.org # v4.6+
> > Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics