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Message-ID: <c2be661a-87e4-864e-3571-75032484f66f@linaro.org>
Date:   Tue, 13 Dec 2022 16:44:15 +0100
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Subject: Re: [PATCH 1/4] arm64: dts: qcom: sc8280xp: rename i2c5 to i2c21
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To:     Johan Hovold <johan@kernel.org>,
        Shazad Hussain <quic_shazhuss@quicinc.com>
Cc:     Brian Masney <bmasney@redhat.com>, andersson@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, robh+dt@kernel.org,
        johan+linaro@kernel.org, linux-arm-msm@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        ahalaney@redhat.com, echanude@redhat.com
References: <20221212182314.1902632-1-bmasney@redhat.com>
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 <Y5iSDehp72mQPc+h@hovoldconsulting.com> <Y5iWeTk2zOp9rInx@x1>
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 <Y5icyo7I5ZGAL02q@hovoldconsulting.com>
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From:   Konrad Dybcio <konrad.dybcio@linaro.org>
In-Reply-To: <Y5idf5dP2ttBSOUa@hovoldconsulting.com>
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On 13.12.2022 16:42, Johan Hovold wrote:
> On Tue, Dec 13, 2022 at 04:39:54PM +0100, 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:
> 
>>>>> 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?
> 
> Looks like the more recent Qualcomm platforms use aliases that reflect
> the engine number (i.e. 0 to 23) for i2c and spi.
IMO it makes the most sense, as it tells the userspace "hello, this
device is connected to the physical I2Cn on the SoC" as opposed to
"hello, this device is connected to the nth enabled bus on this
particular board".

Konrad
> 
> Johan