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Sender: Guenter Roeck <groeck7@gmail.com>
Message-ID: <e51de5ee-5342-8771-46a3-34d8ee8b9c55@roeck-us.net>
Date:   Tue, 25 Jul 2023 07:28:04 -0700
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Subject: Re: [PATCH 1/3] dt-bindings: hwmon: Add Infineon TDA38640
Content-Language: en-US
To:     Naresh Solanki <naresh.solanki@9elements.com>,
        Rob Herring <robh@kernel.org>
Cc:     Jean Delvare <jdelvare@suse.com>,
        krzysztof.kozlowski+dt@linaro.org,
        Conor Dooley <conor+dt@kernel.org>,
        linux-hwmon@vger.kernel.org,
        Patrick Rudolph <patrick.rudolph@9elements.com>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20230725114030.1860571-1-Naresh.Solanki@9elements.com>
 <20230725131006.GA2879331-robh@kernel.org>
 <CABqG17iChAyb0gzb2uXfsv5GkiM3a+LoSavdqhjvw3FUccaw8A@mail.gmail.com>
From:   Guenter Roeck <linux@roeck-us.net>
In-Reply-To: <CABqG17iChAyb0gzb2uXfsv5GkiM3a+LoSavdqhjvw3FUccaw8A@mail.gmail.com>
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On 7/25/23 07:17, Naresh Solanki wrote:
> Hi Rob,
> 
> 
> On Tue, 25 Jul 2023 at 18:40, Rob Herring <robh@kernel.org> wrote:
>>
>> On Tue, Jul 25, 2023 at 01:40:26PM +0200, Naresh Solanki wrote:
>>> From: Patrick Rudolph <patrick.rudolph@9elements.com>
>>>
>>> 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@9elements.com>
>>> Signed-off-by: Naresh Solanki <Naresh.Solanki@9elements.com>
>>> ---
>>>   .../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
>>>