linux-kernel - Re: [PATCH 1/6] dt-bindings: mfd: add bindings for QIXIS CPLD

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Message-ID: <959b56f0-ff63-485b-86eb-96ae32bdeb88@kernel.org>
Date: Tue, 6 May 2025 16:05:46 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Ioana Ciornei <ioana.ciornei@....com>
Cc: Lee Jones <lee@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/6] dt-bindings: mfd: add bindings for QIXIS CPLD

On 06/05/2025 15:57, Ioana Ciornei wrote:
> On Fri, May 02, 2025 at 09:01:59AM +0200, Krzysztof Kozlowski wrote:
>> On Wed, Apr 30, 2025 at 06:36:29PM GMT, Ioana Ciornei wrote:
>>> This adds device tree bindings for the board management controller -
>>> QIXIS CPLD - found on some Layerscape based boards such as LX2160A-RDB,
>>> LX2160AQDS, LS1028AQDS etc.
>>>
>>> Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>
>>> ---
>>>  .../bindings/mfd/fsl,qixis-i2c.yaml           | 65 +++++++++++++++++++
>>>  1 file changed, 65 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/mfd/fsl,qixis-i2c.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/mfd/fsl,qixis-i2c.yaml b/Documentation/devicetree/bindings/mfd/fsl,qixis-i2c.yaml
>>> new file mode 100644
>>> index 000000000000..562878050916
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/mfd/fsl,qixis-i2c.yaml
>>
>> Filename matching compatible.
> 
> How to choose one if there are multiple compatible strings?

The fallback or the oldest or the lowest number or whichever you prefer
as a base.

> 
>>
>>> @@ -0,0 +1,65 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/mfd/fsl,qixis-i2c.yaml
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml
>>> +
>>> +title: NXP's QIXIS CPLD board management controller
>>> +
>>> +maintainers:
>>> +  - Ioana Ciornei <ioana.ciornei@....com>
>>> +
>>> +description: |
>>> +  The board management controller found on some Layerscape boards contains
>>> +  different IP blocks like GPIO controllers, interrupt controllers, reg-muxes
>>> +  etc.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - fsl,lx2160a-qds-qixis-i2c
>>> +      - fsl,lx2162a-qds-qixis-i2c
>>> +      - fsl,ls1028a-qds-qixis-i2c
>>
>> Keep alphabetical order.
>>
>> What is actual device name? I2C? Is this an I2C controller or device?

I assume you will then drop the redundant part.

>>
>>> +
>>> +  reg:
>>> +    description:
>>> +      I2C device address.
>>
>> This says device, so i2c in compatible is wrong.
>>
>> Anyway drop description, redundant.
> 
> Ok, will drop.
> 
>>
>>
>>> +    maxItems: 1
>>> +
>>> +  "#address-cells":
>>> +    const: 1
>>
>> Why?
>>
>>> +
>>> +  "#size-cells":
>>> +    const: 0
>>
>> Why? Drop cells.
>>
> 
> See below.
> 
>>> +
>>> +  mux-controller:
>>> +    $ref: /schemas/mux/reg-mux.yaml#
>>> +
>>> +required:
>>> +  - "#address-cells"
>>> +  - "#size-cells"
>>> +  - compatible
>>> +  - reg
>>
>> Keep same order as in properties
> 
> Ok.
> 
>>
>>> +
>>> +additionalProperties: false
>>> +
>>> +examples:
>>> +  - |
>>> +    i2c {
>>> +        #address-cells = <1>;
>>> +        #size-cells = <0>;
>>> +
>>> +        qixis@66 {
>>
>> Node names should be generic. See also an explanation and list of
>> examples (not exhaustive) in DT specification:
>> https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation
> 
> In this case, an accepted node name is 'cpld'?

If this is CPLD then yes.

> 
>>
>>> +            compatible = "fsl,lx2160a-qds-qixis-i2c";
>>> +            reg = <0x66>;
>>> +            #address-cells = <1>;
>>> +            #size-cells = <0>;
>>
>> So were do you use address/size cells?
>>
> 
> For example, fsl-ls1028a-qds.dts looks like this:
> 
> 	fpga@66 {
> 		compatible = "fsl,ls1028a-qds-qixis-i2c";
> 		reg = <0x66>;
> 		#address-cells = <1>;
> 		#size-cells = <0>;
> 
> 		mux: mux-controller@54 {
> 			compatible = "reg-mux";
> 			reg = <0x54>;
> 			#mux-control-cells = <1>;
> 			mux-reg-masks = <0x54 0xf0>; /* 0: reg 0x54, bits 7:4 */
> 		};
> 	};
> 
> Also, some boards have in their qixis CPLD gpio controllers and I am
> planning to add them as the next step.

And if you tested that DTS you would see that binding does not work
well... so my arguments stay valid - these properties in current binding
make no sense. However binding is just wrong, so maybe these properties
make sense after fixing the binding but then in both cases: current
stage is not correct.

> 
> Ioana


Best regards,
Krzysztof