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

Niklas <niklas.soderlund@...>

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@...>

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.


+++ b/drivers/thermal/rcar_gen3_thermal.c
@@ -182,9 +182,7 @@ static int rcar_gen3_thermal_get_temp(void
*devdata, int *temp)
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);
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Niklas Söderlund

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