linux-kernel - Re: [PATCH v5 1/2] dt-bindings: i2c: Add support for ASPEED i2Cv2

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Message-ID: <e2765493-0502-8c6d-39ce-e59581131dbf@linaro.org>
Date:   Mon, 20 Feb 2023 11:43:53 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Ryan Chen <ryan_chen@...eedtech.com>,
        Jeremy Kerr <jk@...econstruct.com.au>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 1/2] dt-bindings: i2c: Add support for ASPEED i2Cv2

On 20/02/2023 10:50, Ryan Chen wrote:
>> These are common to all i2c controllers, but I see that i2c-controller.yaml
>> doesn't include them (while i2c.text does).
>>
>> I assume we're OK to include these in the device bindings in the meantime.
>> But in that case, you may also want to include the common "smbus-alert"
>> property, which you consume in your driver.
>>
> Since i2c.text have multi-master, smbus-alert. I don't need those two right?

Yes, these should be dropped.

> 
>>> +  timeout:
>>> +    type: boolean
>>> +    description: Enable i2c bus timeout for master/slave (35ms)
>>> +
>>> +  byte-mode:
>>> +    type: boolean
>>> +    description: Force i2c driver use byte mode transmit
>>> +
>>> +  buff-mode:
>>> +    type: boolean
>>> +    description: Force i2c driver use buffer mode transmit
>>
>> These three aren't really a property of the hardware, more of the intended
>> driver configuration. Do they really belong in the DT?
>>
> Sorry, I am confused. 
> This is hardware controller mode setting for each i2c transfer. 
> So I add it in property for change different i2c transfer mode.
> Is my mis-understand the property setting?

You described the property as "Force I2C driver", so it is a not correct
description. DTS is not for controlling driver. You must describe here
hardware feature/property, not driver behavior. Also, it must be clear
for us why this is being customized per each board.

> 
>> [and how would a DT author know which modes to choose?]

Exactly.


Best regards,
Krzysztof