Re: [cip-dev] [PATCH 4.19.y-cip 02/10] thermal: rcar_gen3_thermal: Remove temperature bound

[Niklas <niklas.soderlund@ragnatech.se>]

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Hi Biju,

On 2020-08-26 07:40:46 +0000, Biju Das wrote:
> Hi Pavel,
> 
> Thanks for the feedback.
> 
> > Subject: Re: [PATCH 4.19.y-cip 02/10] thermal: rcar_gen3_thermal: Remove
> > temperature bound
> >
> > On Tue 2020-08-25 14:21:48, Biju Das wrote:
> > > From: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > >
> > > commit 0f510a2457cbbba18a98492bab1bf540be57ebd1 upstream.
> > >
> > > The hardware manual states that the operation of the sensor is not
> > > guaranteed with temperatures above 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.
> >
> > I'm tempted to ask "how was this tested?" :-).
> >
> > Sometimes sensors have glitches producing very high values in normal
> > temperatures, and it such case clamping can be useful, but I'll assume your
> > sensor works ok.
> 
> Niklas,  Can you please clarify?

IIRC I was asked to remove the clamp as the hardware team had tested the 
sensors in a wider range and it was judged better to report a reading 
even if it was not guaranteed then to clamp it. I have not been able 
myself to test this change myself and rely on the report from the 
hardware team.

> 
> Cheers,
> Biju
> 
> 
> 
> >
> > > +++ b/drivers/thermal/rcar_gen3_thermal.c
> > > @@ -182,9 +182,7 @@ static int rcar_gen3_thermal_get_temp(void
> > *devdata, int *temp)
> > >  tsc->coef.a2);
> > >  mcelsius = FIXPT_TO_MCELSIUS(val);
> > >
> > > -/* Make sure we are inside specifications */
> > > -if ((mcelsius < MCELSIUS(-40)) || (mcelsius > MCELSIUS(125)))
> > > -return -EIO;
> > > +/* Guaranteed operating range is -40C to 125C. */
> > >
> > >  /* Round value to device granularity setting */
> > >  *temp = rcar_gen3_thermal_round(mcelsius);
> >
> > --
> > DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> > HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> 
> 
> Renesas Electronics Europe GmbH, Geschaeftsfuehrer/President: Carsten Jauch, Sitz der Gesellschaft/Registered office: Duesseldorf, Arcadiastrasse 10, 40472 Duesseldorf, Germany, Handelsregister/Commercial Register: Duesseldorf, HRB 3708 USt-IDNr./Tax identification no.: DE 119353406 WEEE-Reg.-Nr./WEEE reg. no.: DE 14978647

-- 
Regards,
Niklas Söderlund

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