linux-kernel - Re: [EXT] Re: [PATCH 2/2] dt-bindings: i2c: imx-lpi2c: Add bus recovery example

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Date:   Wed, 31 May 2023 21:50:01 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Carlos Song <carlos.song@....com>,
        Aisheng Dong <aisheng.dong@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "Anson.Huang@....com" <Anson.Huang@....com>
Cc:     Clark Wang <xiaoning.wang@....com>,
        Bough Chen <haibo.chen@....com>,
        dl-linux-imx <linux-imx@....com>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [EXT] Re: [PATCH 2/2] dt-bindings: i2c: imx-lpi2c: Add bus
 recovery example

On 31/05/2023 12:22, Carlos Song wrote:
> Hi,
> 	Thanks for you reply. 
>> -----Original Message-----
>> From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>> Sent: Tuesday, May 30, 2023 10:59 PM
>> To: Carlos Song <carlos.song@....com>; Aisheng Dong
>> <aisheng.dong@....com>; shawnguo@...nel.org; s.hauer@...gutronix.de;
>> kernel@...gutronix.de; festevam@...il.com; robh+dt@...nel.org;
>> krzysztof.kozlowski+dt@...aro.org; conor+dt@...nel.org;
>> Anson.Huang@....com
>> Cc: Clark Wang <xiaoning.wang@....com>; Bough Chen
>> <haibo.chen@....com>; dl-linux-imx <linux-imx@....com>;
>> linux-i2c@...r.kernel.org; devicetree@...r.kernel.org;
>> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
>> Subject: [EXT] Re: [PATCH 2/2] dt-bindings: i2c: imx-lpi2c: Add bus recovery
>> example
>>
>> Caution: This is an external email. Please take care when clicking links or
>> opening attachments. When in doubt, report the message using the 'Report this
>> email' button
>>
>>
>> On 29/05/2023 09:43, carlos.song@....com wrote:
>>> From: Clark Wang <xiaoning.wang@....com>
>>>
>>> Add i2c bus recovery configuration example.
>>
>> Why? That's just example... also with coding style issue.
>>
>>>
>>> Signed-off-by: Clark Wang <xiaoning.wang@....com>
>>> Signed-off-by: Carlos Song <carlos.song@....com>
>>> ---
>>>  .../devicetree/bindings/i2c/i2c-imx-lpi2c.yaml   | 16 ++++++++++++++++
>>>  1 file changed, 16 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/i2c/i2c-imx-lpi2c.yaml
>>> b/Documentation/devicetree/bindings/i2c/i2c-imx-lpi2c.yaml
>>> index 4656f5112b84..62ee457496e4 100644
>>> --- a/Documentation/devicetree/bindings/i2c/i2c-imx-lpi2c.yaml
>>> +++ b/Documentation/devicetree/bindings/i2c/i2c-imx-lpi2c.yaml
>>> @@ -58,6 +58,16 @@ properties:
>>>    power-domains:
>>>      maxItems: 1
>>>
>>> +  pinctrl-names:
>>> +    minItems: 1
>>> +    maxItems: 3
>>
>> What's the benefit of this? Entries should be defined but without it is not really
>> helpful. Anyway not explained in commit msg.
>>
>>> +
>>> +  scl-gpios:
>>> +    maxItems: 1
>>> +
>>> +  sda-gpios:
>>> +    maxItems: 1
>>
>> You don't need these two. Anyway not explained in commit msg.
>>
> 
> Sorry for confusing you with the poor commit log and without
> full description.
> 
> The reason why we need sending the patch for dt-binding is :
> We sent out a patch for I.MX LPI2C bus support recovery function.
> When LPI2C use recovery function, lpi2c controller need to switch the 
> SCL pin and SDA pin to their GPIO function.  So I think the scl-gpio and
> sda-gpio property need to be added in the dt-bindings.

Why do you think they are not in the bindings already?

> 
> And alternative pinmux settings are described in a separate pinctrl state "gpio". 
> So maybe "gpio" pinctrl item need to be added.
> 
> I would like to know whether the above changes are really unnecessary according to above case?
> Or because of the vague commit log, you are misled and think that our patch is not necessary to add examples.


I claim your patch has zero effect. Can you prove otherwise?

Proof is with DTS example and result of dtbs_check.

> 
> Is there no need to add sda/scl-gpios property or no need to add maxItems: 1?

I think entire patch can be dropped.

> We also find the sci-gpio and sda-gpio have been defined in the ref: /schemas/i2c/i2c-controller.yaml. 
> So is this the root cause of no need to add these properties?

Yes.


Best regards,
Krzysztof