Re: [PATCH v5 1/9] dt-bindings: thermal: qcom: add adc-thermal monitor bindings

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Wed, 23 Sep 2020 08:00:29 -0600
Rob Herring <robh@kernel.org> wrote:

> On Wed, Sep 23, 2020 at 3:07 AM Dmitry Baryshkov
> <dmitry.baryshkov@linaro.org> wrote:
> >
> > On 23/09/2020 02:40, Rob Herring wrote:  
> > > On Mon, Sep 14, 2020 at 06:48:01PM +0300, Dmitry Baryshkov wrote:  
> > >> Add bindings for thermal monitor, part of Qualcomm PMIC5 chips. It is a
> > >> close counterpart of VADC part of those PMICs.
> > >>
> > >> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> > >> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > >> ---
> > >>   .../bindings/thermal/qcom-spmi-adc-tm5.yaml   | 151 ++++++++++++++++++
> > >>   1 file changed, 151 insertions(+)
> > >>   create mode 100644 Documentation/devicetree/bindings/thermal/qcom-spmi-adc-tm5.yaml
> > >>
> > >> diff --git a/Documentation/devicetree/bindings/thermal/qcom-spmi-adc-tm5.yaml b/Documentation/devicetree/bindings/thermal/qcom-spmi-adc-tm5.yaml
> > >> new file mode 100644
> > >> index 000000000000..432a65839b89
> > >> --- /dev/null
> > >> +++ b/Documentation/devicetree/bindings/thermal/qcom-spmi-adc-tm5.yaml
> > >> @@ -0,0 +1,151 @@
> > >> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > >> +%YAML 1.2
> > >> +---
> > >> +$id: http://devicetree.org/schemas/thermal/qcom-spmi-adc-tm5.yaml#
> > >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > >> +
> > >> +title: Qualcomm's SPMI PMIC ADC Thermal Monitoring
> > >> +maintainers:
> > >> +  - Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> > >> +
> > >> +properties:
> > >> +  compatible:
> > >> +    const: qcom,spmi-adc-tm5
> > >> +
> > >> +  reg:
> > >> +    maxItems: 1
> > >> +
> > >> +  interrupts:
> > >> +    maxItems: 1
> > >> +
> > >> +  "#thermal-sensor-cells":
> > >> +    const: 1
> > >> +    description:
> > >> +      Number of cells required to uniquely identify the thermal sensors. Since
> > >> +      we have multiple sensors this is set to 1
> > >> +
> > >> +  "#address-cells":
> > >> +    const: 1
> > >> +
> > >> +  "#size-cells":
> > >> +    const: 0
> > >> +
> > >> +  qcom,avg-samples:
> > >> +    $ref: /schemas/types.yaml#/definitions/uint32
> > >> +    description: Number of samples to be used for measurement.
> > >> +    enum:
> > >> +      - 1
> > >> +      - 2
> > >> +      - 4
> > >> +      - 8
> > >> +      - 16
> > >> +    default: 1
> > >> +
> > >> +  qcom,decimation:
> > >> +    $ref: /schemas/types.yaml#/definitions/uint32
> > >> +    description: This parameter is used to decrease ADC sampling rate.
> > >> +            Quicker measurements can be made by reducing decimation ratio.
> > >> +    enum:
> > >> +      - 250
> > >> +      - 420
> > >> +      - 840
> > >> +    default: 840
> > >> +
> > >> +patternProperties:
> > >> +  "^([-a-z0-9]*)@[0-9]+$":  
> > >
> > > Less than 10 as unit-addresses are hex?  
> >
> > 8 channels at max currently. I'll fix to use hex though.  
> 
> Then it should be @[0-7]$
> 
> > >> +    type: object
> > >> +    description:
> > >> +      Represent one thermal sensor.
> > >> +
> > >> +    properties:
> > >> +      reg:
> > >> +        description: Specify the sensor channel.
> > >> +        maxItems: 1  
> > >
> > > You need a range of values here.  
> >
> > ok.
> >  
> > >  
> > >> +
> > >> +      io-channels:
> > >> +        description:
> > >> +          From common IIO binding. Used to pipe PMIC ADC channel to thermal monitor
> > >> +
> > >> +      qcom,adc-channel:
> > >> +        $ref: /schemas/types.yaml#/definitions/uint32
> > >> +        description: Corresponding ADC channel ID.  
> > >
> > > Why is this not a cell in io-channels?  
> >
> >
> > Do you mean parsing a cell from io-channels rather than specifying it
> > again? Sounds like a good idea.  
> 
> Yes.
> 
> > >> +      qcom,ratiometric:
> > >> +        $ref: /schemas/types.yaml#/definitions/flag
> > >> +        description:
> > >> +          Channel calibration type.
> > >> +          If this property is specified VADC will use the VDD reference
> > >> +          (1.875V) and GND for channel calibration. If property is not found,
> > >> +          channel will be calibrated with 0V and 1.25V reference channels,
> > >> +          also known as absolute calibration.
> > >> +
> > >> +      qcom,hw-settle-time:
> > >> +        $ref: /schemas/types.yaml#/definitions/uint32
> > >> +        description: Time between AMUX getting configured and the ADC starting conversion.  
> > >
> > > Time values should have a unit suffix. Seems like a commmon ADC
> > > property...  
> >
> > Could you please be more specific here? Would you like for me to just
> > specify the unit in the description?  
> 
> More a question for Jonathan I guess as to whether this should be
> common or not. Maybe we have something already. Settle or acquisition
> time is a common thing for ADCs, right?

It's not common in my experience, but not unheard of.
Only cases currently supporting controlling it explicitly in the
kernel that I can spot, are currently all qcom parts
(I'd guess they are all using the same IP underneath)

I think it is usually it's a case of building your analog
circuitry to match the spec of your ADC / MUX rather than
relaxing that spec by adding a delay.

It's a property with obvious enough meaning though that I
wouldn't have a problem with it being a generic property even
it is one that doesn't actually get used much.

> 
> Properties with units need a suffix as defined in
> .../bindings/property-units.txt.

We have a bunch of legacy bindings that don't have units but
all new ones certainly should!

Thanks,

Jonathan

> 
> Rob