linux-kernel - Re: [PATCH 1/4] arm64: dts: qcom: sc8280xp: rename i2c5 to i2c21

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Date:   Tue, 13 Dec 2022 21:15:32 +0530
From:   Shazad Hussain <quic_shazhuss@...cinc.com>
To:     Johan Hovold <johan@...nel.org>
CC:     Brian Masney <bmasney@...hat.com>, <andersson@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <konrad.dybcio@...aro.org>,
        <robh+dt@...nel.org>, <johan+linaro@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <ahalaney@...hat.com>,
        <echanude@...hat.com>
Subject: Re: [PATCH 1/4] arm64: dts: qcom: sc8280xp: rename i2c5 to i2c21



On 12/13/2022 9:09 PM, Johan Hovold wrote:
> On Tue, Dec 13, 2022 at 09:04:39PM +0530, Shazad Hussain wrote:
>>
>>
>> On 12/13/2022 8:58 PM, Johan Hovold wrote:
>>> On Tue, Dec 13, 2022 at 10:12:57AM -0500, Brian Masney wrote:
>>>> On Tue, Dec 13, 2022 at 03:54:05PM +0100, Johan Hovold wrote:
>>>>> Note that the node is labelled qup2_i2c5 and not qup_i2c5.
>>>>>
>>>>> That is, the QUP nodes are labelled using two indices, and specifically
>>>>>
>>>>> 	qup2_i2c5
>>>>>
>>>>> would be another name for
>>>>>
>>>>> 	qup_i2c21
>>>>>
>>>>> if we'd been using such a flat naming scheme (there are 8 engines per
>>>>> QUP).
>>>>>
>>>>> So there's nothing wrong with how these nodes are currently named, but
>>>>> mixing the two scheme as you are suggesting would not be correct.
>>>>
>>>> Hi Johan,
>>>>
>>>> What would I use for the name in the aliases section? Right now I have:
>>>>
>>>>       aliases {
>>>>           i2c18 = &qup2_i2c18;
>>>>       }
>>>>
>>>> So qup2_i2c18 becomes qup2_i2c2. Would I use the flat naming scheme for
>>>> the alias like so?
>>>>
>>>>       aliases {
>>>>           i2c18 = &qup2_i2c2;
>>>>       }
>>>
>>> Or perhaps the i2c controllers should use a zero-based index instead of
>>> being named after the serial engines (e.g. as we do for the console
>>> uart).
>>>
>>> How are they named in the schematics?
>>
>> We should use from 0 to N.
> 
> With N being 23 after the number of serial engines, or the number of
> available i2c buses on a particular board minus one?
> 

wrt to serial engine number starting from 0.

Shazad

> Johan