Re: [PATCH v16 1/3] dt-bindings: i2c: aspeed: support for AST2600-i2cv2

Krzysztof Kozlowski
2025-02-26T09:56:43Z

On 26/02/2025 10:28, Ryan Chen wrote:
>> Subject: Re: [PATCH v16 1/3] dt-bindings: i2c: aspeed: support for
>> AST2600-i2cv2
>>
>> On Mon, Feb 24, 2025 at 01:59:34PM +0800, Ryan Chen wrote:
>>> Add ast2600-i2cv2 compatible and aspeed,global-regs, aspeed,enable-dma
>>> and description for ast2600-i2cv2.
>>>
>>> Signed-off-by: Ryan Chen <ryan_chen@aspeedtech.com>
>>> ---
>>> .../devicetree/bindings/i2c/aspeed,i2c.yaml | 58 +++++++++++++++++++
>>> 1 file changed, 58 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml
>>> b/Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml
>>> index 5b9bd2feda3b..356033d18f90 100644
>>> --- a/Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml
>>> +++ b/Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml
>>> @@ -44,12 +44,60 @@ properties:
>>> description: frequency of the bus clock in Hz defaults to 100 kHz when
>> not
>>> specified
>>>
>>> + multi-master:
>>> + type: boolean
>>> + description:
>>> + states that there is another master active on this bus
>>
>> Except that this wasn't ever tested...
>>
>> Don't duplicate properties. i2c-controller schema has it already.
>
> I will remove it to avoid duplication.
>>
>>> +
>>> + aspeed,enable-dma:
>>> + type: boolean
>>> + description: |
>>> + I2C bus enable dma mode transfer.
>>> +
>>> + ASPEED ast2600 platform equipped with 16 I2C controllers that
>> share a
>>> + single DMA engine. DTS files can specify the data transfer mode
>> to/from
>>> + the device, either DMA or programmed I/O. However, hardware
>>> + limitations
>>
>> so what is byte mode?
> I explain in cover, I will add here also.

Cover letters do not get merged and we do not read them, except when
looking for dependencies and explanations of process (like RFC). Your
hardware description must be fully contained in commits, not cover letter.

> aspeed,enable-byte:
> Force i2c controller use byte mode transfer. the byte mode transfer
> will send i2c data each byte by byte, inlcude address read/write.

Isn't this standard FIFO mode?

Why anyone would need to enable byte mode for given board?

>
>>
>>> + may require a DTS to manually allocate which controller can use
>> DMA mode.
>>> + The "aspeed,enable-dma" property allows control of this.
>>> +
>>> + In cases where one the hardware design results in a specific
>>> + controller handling a larger amount of data, a DTS would likely
>>> + enable DMA mode for that one controller.
>>> +
>>> + aspeed,enable-byte:
>>> + type: boolean
>>> + description: |
>>> + I2C bus enable byte mode transfer.
>>
>> No, either this is expressed as lack of dma mode property or if you have three
>> modes, then rather some enum (aspeed,transfer-mode ?)
>
> Thanks suggestion, I will using an enum property like aspeed,transfer-mode instead.
>>
>>
>>
>>> +
>>> + aspeed,global-regs:
>>> + $ref: /schemas/types.yaml#/definitions/phandle
>>> + description: The phandle of i2c global register node.
>>
>> For what? Same question as usual: do not repeat property name, but say what
>> is this used for and what exactly it points to.
>>
>> s/i2c/I2C/ but then what is "I2C global register node"? This is how you call your
>> device in datasheet?
>>
> I do descript in cover, should add into the yaml file ?

Again, cover letter does not matter. Your hardware must be explained here.

>
> aspeed,global-regs:
> This global register is needed, global register is setting for
> new clock divide control, and new register set control.

So this means you implement clock controller via syscon?

>
>>
>>> +
>>> required:
>>> - reg
>>> - compatible
>>> - clocks
>>> - resets
>>>
>>> +allOf:
>>> + - $ref: /schemas/i2c/i2c-controller.yaml#
>>> + - if:
>>> + properties:
>>> + compatible:
>>> + contains:
>>> + const: aspeed,ast2600-i2cv2
>>
>> NAK, undocumented compatible.
>
> Sorry, I should add what kind of document about this compatible?

You cannot add new compatibles without documenting them. Documentation
is in the form of DT schema and each compatible must be listed (in some
way) in compatible property description.

Best regards,
Krzysztof