Re: [PATCH v6 3/5] thermal: renesas: rzg3e: Add thermal driver for the Renesas RZ/G3E SoC

[Daniel Lezcano <daniel.lezcano@linaro.org>]

Hi John,


On 05/08/2025 09:49, John Madieu wrote:

[ ... ]

>>> I might not get what you are asking, but since I compute the
>>> temperature in the hard IRQ handler, I just wait for it to complete
>>> and notify the completion so I can grab the processed value to notify
>>> the thermal core.
>>>
>>> Please let me know if this does not answer your question.
>>
>> Can you describe how the sensor works ? And perhaps if you have a pointer
>> to some documentation ?
> 
> Here is the documentation [1]. The thermal device is referred to as TSU.
> 
> [1] https://www.renesas.com/en/document/mah/rzg3e-group-users-manual-hardware?r=25574493
> 
>>    [ ... ]

Thanks for the pointer. I got it now ;)

I'm a bit worried about the latency introduced by this mechanism when 
the system is entering in a thermal pressure episode.

The get_temp function wait for a completion up to 100ms, it is a lot. 
Especially if the userspace can be reading the temperature and blocking 
the read.

There is also the spin_lock taken introducing another lock while the 
get_temp function is holding a mutex on the thermal zone.

Did you it that under stress ?

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