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Subject: Re: [PATCH v7 00/11] Stop monitoring disabled devices
To:     Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
        Zhang Rui <rui.zhang@intel.com>, linux-pm@vger.kernel.org,
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Cc:     "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>,
        Vishal Kulkarni <vishal@chelsio.com>,
        "David S . Miller" <davem@davemloft.net>,
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        Allison Randal <allison@lohutok.net>,
        Enrico Weigelt <info@metux.net>,
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        Thomas Gleixner <tglx@linutronix.de>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
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From:   Daniel Lezcano <daniel.lezcano@linaro.org>
Message-ID: <9fcd1d07-26af-4ff3-56d7-7226ef42a7e6@linaro.org>
Date:   Fri, 3 Jul 2020 13:05:06 +0200
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On 03/07/2020 12:45, Andrzej Pietrasiewicz wrote:
> Hi,
> 
> W dniu 03.07.2020 o 08:38, Daniel Lezcano pisze:
>> On 03/07/2020 03:49, Zhang Rui wrote:
>>> On Thu, 2020-07-02 at 19:49 +0200, Daniel Lezcano wrote:
>>
>> [ ... ]
>>
>>>>> So the reason is that ->get_temp() is called while the mutex is
>>>>> held and
>>>>> thermal_zone_device_is_enabled() wants to take the same mutex.
>>>>
>>>> Yes, that's correct.
>>>>
>>>>> Is adding a comment to thermal_zone_device_is_enabled() to never
>>>>> call
>>>>> it while the mutex is held and adding another version of it which
>>>>> does
>>>>> not take the mutex ok?
>>>>
>>>> The thermal_zone_device_is_enabled() is only used in two places, acpi
>>>> and this imx driver, and given:
>>>>
>>>> 1. as soon as the mutex is released, there is no guarantee the
>>>> thermal
>>>> zone won't be changed right after, the lock is pointless, thus the
>>>> information also.
>>>>
>>>> 2. from a design point of view, I don't see why a driver should know
>>>> if
>>>> a thermal zone is disabled or not
>>>>
>>>> It would make sense to end with this function and do not give the
>>>> different drivers an opportunity to access this information.
>>>
>>> I agree.
>>>>
>>>> Why not add change_mode for the acpi in order to enable or disable
>>>> the
>>>> events
>>>
>>> thermal_zone_device_is_enabled() is invoked in acpi thermal driver
>>> because we only want to do thermal_zone_device_update() when the acpi
>>> thermal zone is enabled.
>>>
>>> As thermal_zone_device_update() can handle a disabled thermal zone now,
>>> we can just remove the check.
>>
>> Ah yes, good point!
>>
>>
>>
> 
> I sent a short series with fixes. Daniel, can you kindly test it?

I confirm the i.MX is now correctly booting with the thermal zone
temperature available.


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