Re: [PATCH v2 1/2] dt-bindings: thermal: imx: Document calibration offset property

[Conor Dooley <conor@kernel.org>]

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On Thu, Jul 09, 2026 at 10:07:21AM -0500, Frank Li wrote:
> On Thu, Jul 09, 2026 at 04:10:21PM +0800, HaoNing Cheng via B4 Relay wrote:
> > [You don't often get email from devnull+haoning.cheng.cn.bosch.com@kernel.org. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> >
> > From: HaoNing Cheng <Haoning.CHENG@cn.bosch.com>
> >
> > Some boards need a small per-design correction to align the reported CPU
> > temperature with board-level measurements.
> >
> > Document the optional fsl,temp-calibration-offset-millicelsius property,
> > a signed offset in millicelsius that is added to the calculated sensor
> > temperature.
> 
> why board difference cause such offset, I suppose it is cause by SoC
> variance. The offset may difference if you change to another chip. another
> words, if you have 1000 boards, Is this offset the same?

I think your "in other words" section here is confusing.
You're asking about "1000 boards", which would imply that it is 1000 of
the same design of board. The commit message says that the variance is
between designs. If 1000 of the same design of board have the same offset,
but 2 boards with different designs have different ones then this
property seems fair. Of course, if the variance is determined by the SoC
in use, then this should be deduced from the compatible, but the commit
message seems to be fairly clear about it not being SoC related.

> 
> 
> > The property is optional and the existing behaviour is kept
> > when it is omitted.
> >
> > Update the binding example to show its usage.
> >
> > Signed-off-by: HaoNing Cheng <Haoning.CHENG@cn.bosch.com>
> > ---
> >  Documentation/devicetree/bindings/thermal/imx-thermal.yaml | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/thermal/imx-thermal.yaml b/Documentation/devicetree/bindings/thermal/imx-thermal.yaml
> > index 949b154856c5..eb7243a7ebaf 100644
> > --- a/Documentation/devicetree/bindings/thermal/imx-thermal.yaml
> > +++ b/Documentation/devicetree/bindings/thermal/imx-thermal.yaml
> > @@ -59,6 +59,13 @@ properties:
> >    clocks:
> >      maxItems: 1
> >
> > +  fsl,temp-calibration-offset-millicelsius:
> > +    maxItems: 1
> 
> suppose it int32, why need maxItems here?

  "-millicelsius$":
    $ref: types.yaml#/definitions/int32-array

What's missing are constraints on the max and min I think though.
pw-bot: changes-requested

Thanks,
Conor.

> 
> Frank
> 
> > +    description:
> > +      A signed calibration offset, in millicelsius, added to the calculated
> > +      sensor temperature to compensate for board-level measurement
> > +      differences. When absent, no offset is applied.
> > +
> >    "#thermal-sensor-cells":
> >      const: 0
> >
> > @@ -109,6 +116,7 @@ examples:
> >              nvmem-cells = <&tempmon_calib>, <&tempmon_temp_grade>;
> >              nvmem-cell-names = "calib", "temp_grade";
> >              clocks = <&clks IMX6SX_CLK_PLL3_USB_OTG>;
> > +            fsl,temp-calibration-offset-millicelsius = <(-6400)>;
> >              #thermal-sensor-cells = <0>;
> >          };
> >      };
> >
> > --
> > 2.43.0
> >
> >
> >

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