Re: [PATCH 1/3] dt-bindings: hwmon: Add Infineon TDA38640

[Guenter Roeck]

On 7/25/23 07:17, Naresh Solanki wrote:
> Hi Rob,
>
>
> On Tue, 25 Jul 2023 at 18:40, Rob Herring <robh@xxxxxxxxxx> wrote:
> > On Tue, Jul 25, 2023 at 01:40:26PM +0200, Naresh Solanki wrote:
> > > From: Patrick Rudolph <patrick.rudolph@xxxxxxxxxxxxx>
> > >
> > > The TDA38640 has a bug in SVID mode and to enable a workaround
> > > remove the TDA38640 from trivial-devices and add a complete schema.
> > >
> > > The schema adds the custom property 'infineon,en-pin-fixed-level' to
> > > signal a fixed level on the ENABLE pin and to enable the workaround.
> > > When the ENABLE pin is left floating it's internally pulled low.
> > >
> > > If not specified the driver will continue to use the PMBUS_OPERATION
> > > register to enable the regulator. When specified the driver will use
> > > the PMBUS_ON_OFF_CONFIG register to enable the regulator.
> > >
> > > Signed-off-by: Patrick Rudolph <patrick.rudolph@xxxxxxxxxxxxx>
> > > Signed-off-by: Naresh Solanki <Naresh.Solanki@xxxxxxxxxxxxx>
> > > ---
> > >   .../hwmon/pmbus/infineon,tda38640.yaml        | 50 +++++++++++++++++++
> > >   .../devicetree/bindings/trivial-devices.yaml  |  2 -
> > >   2 files changed, 50 insertions(+), 2 deletions(-)
> > >   create mode 100644 Documentation/devicetree/bindings/hwmon/pmbus/infineon,tda38640.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/hwmon/pmbus/infineon,tda38640.yaml b/Documentation/devicetree/bindings/hwmon/pmbus/infineon,tda38640.yaml
> > > new file mode 100644
> > > index 000000000000..520112e4e271
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/hwmon/pmbus/infineon,tda38640.yaml
> > > @@ -0,0 +1,50 @@
> > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +
> > > +$id: http://devicetree.org/schemas/hwmon/pmbus/infineon,tda38640.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Infineon TDA38640 Synchronous Buck Regulator with SVID and I2C
> > > +
> > > +description: |
> > > +  The Infineon TDA38640 is a 40A Single-voltage Synchronous Buck
> > > +  Regulator with SVID and I2C designed for Industrial use.
> > > +
> > > +  Datasheet: https://www.infineon.com/dgdl/Infineon-TDA38640-0000-DataSheet-v02_04-EN.pdf?fileId=8ac78c8c80027ecd018042f2337f00c9
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - infineon,tda38640
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  infineon,en-pin-fixed-level:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    description: |
> > > +      Fixed level of the ENABLE pin. When specified the PMBUS_ON_OFF_CONFIG
> > > +      register is used to enable the regulator instead of the PMBUS_OPERATION
> > > +      register to workaround a bug of the tda38640 when operating in SVID-mode.
> > > +      If the ENABLE pin is left floating the internal pull-down causes a low
> > > +      level on the pin.
> >
> > Neither this nor the commit message answers how do I decide if I set
> > this property or not? How you work-around it is not that relevant to the
> > binding.
> Sure will update this as:
> The property becomes relevant when dealing with the tda38640 in
> SVID-mode, providing an alternative method to enable the regulator by
> using the PMBUS_ON_OFF_CONFIG register instead of the PMBUS_OPERATION
> register

As mentioned in the other e-mail, I'll want to see an explanation why
this property is even needed. The series claims that the chip has a bug
in SVID mode. It is kind of unusual that we would enable a workaround
for a bug with a devicetree property if the circumstance (SVID mode)
can be determined automatically.

Guenter

> Regards,
> Naresh
> > > +
> > > +required:
> > > +  - compatible
> > > +  - reg
> > > +
> > > +additionalProperties: false
> > > +
> > > +examples:
> > > +  - |
> > > +    i2c {
> > > +        #address-cells = <1>;
> > > +        #size-cells = <0>;
> > > +
> > > +        tda38640@40 {
> > > +            compatible = "infineon,tda38640";
> > > +            reg = <0x40>;
> > > +        };
> > > +    };
> > > +
> > > diff --git a/Documentation/devicetree/bindings/trivial-devices.yaml b/Documentation/devicetree/bindings/trivial-devices.yaml
> > > index 6e24c4d25ec3..2b1fbb2a672b 100644
> > > --- a/Documentation/devicetree/bindings/trivial-devices.yaml
> > > +++ b/Documentation/devicetree/bindings/trivial-devices.yaml
> > > @@ -151,8 +151,6 @@ properties:
> > >             - infineon,slb9645tt
> > >               # Infineon SLB9673 I2C TPM 2.0
> > >             - infineon,slb9673
> > > -            # Infineon TDA38640 Voltage Regulator
> > > -          - infineon,tda38640
> > >               # Infineon TLV493D-A1B6 I2C 3D Magnetic Sensor
> > >             - infineon,tlv493d-a1b6
> > >               # Infineon Multi-phase Digital VR Controller xdpe11280
> > >
> > > base-commit: 55612007f16b5d7b1fb83a7b0f5bb686829db7c7
> > > --
> > > 2.41.0