Re: [PATCH 1/2] thermal: rcar_thermal: Remove temperature bound

["Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>]

On 2020-01-15 19:52:25 +0100, Daniel Lezcano wrote:
> On 15/01/2020 19:39, Niklas Söderlund wrote:
> > Hi Daniel,
> > 
> > On 2020-01-15 19:15:11 +0100, Daniel Lezcano wrote:
> >> On 15/01/2020 14:45, Niklas Söderlund wrote:
> >>> Hi Daniel,
> >>>
> >>> Thanks for your feedback.
> >>>
> >>> On 2020-01-15 14:24:30 +0100, Daniel Lezcano wrote:
> >>>> On 14/01/2020 23:29, Niklas Söderlund wrote:
> >>>>> The hardware manual states that the operation of the sensor is not
> >>>>> guaranteed outside the range of -40°C to 125°C, not that the readings
> >>>>> are invalid. Remove the bound check and try to deliver temperature
> >>>>> readings even if we are outside the guaranteed operation range.
> >>>>
> >>>> And what if the sensor is returning crap in this out-of-range operation?
> >>>
> >>> I'm not sure what is worse, reporting an untrue (but still outside the 
> >>> guaranteed operation range) extreme temperature or failing with -EIO.  
> >>> The view of the hardware guys is that it's better to report what the 
> >>> sensor indicates then to return -EIO.
> >>
> >> I don't get the point.
> >>
> >> What happens if we read the sensor while it is above or below the limits?
> > 
> > The manual describes the read outs as being +/- 2°C from the true 
> > temperature for the guaranteed operating range. Outside this range the 
> > difference between the true temperature and the read out temperature 
> > might be larger than 2°C.
> 
> Ok, I see the point now. I guess in any case the SoC won't be working
> very well outside of these operating range also.
> 
> It would be interesting to add in the core code a warning when reaching
> the sensor's operating range. Please replace the code deletion in your
> patches by a comment keeping the range values for reference if we add a
> sensor boundaries property later.

Thanks, will do and post a v2.

> 
> Thanks
>   -- Daniel
> 
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-- 
Regards,
Niklas Söderlund