linux-kernel - Re: [PATCH v3 1/4] dt-bindindgs: i2c: qcom,i2c-geni: Document shared flag

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Message-ID: <6d81d8e7-ecd1-46f0-8ca3-617b5ee96990@quicinc.com>
Date: Wed, 13 Nov 2024 21:38:37 +0530
From: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
CC: <konrad.dybcio@...aro.org>, <andersson@...nel.org>,
        <andi.shyti@...nel.org>, <linux-arm-msm@...r.kernel.org>,
        <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-i2c@...r.kernel.org>, <conor+dt@...nel.org>,
        <agross@...nel.org>, <devicetree@...r.kernel.org>, <vkoul@...nel.org>,
        <linux@...blig.org>, <dan.carpenter@...aro.org>, <Frank.Li@....com>,
        <konradybcio@...nel.org>, <bryan.odonoghue@...aro.org>,
        <krzk+dt@...nel.org>, <robh@...nel.org>
Subject: Re: [PATCH v3 1/4] dt-bindindgs: i2c: qcom,i2c-geni: Document shared
 flag



On 9/27/2024 2:54 PM, Krzysztof Kozlowski wrote:
> On Fri, Sep 27, 2024 at 12:01:05PM +0530, Mukesh Kumar Savaliya wrote:
>> Adds qcom,shared-se flag usage. Use this when particular I2C serial
>> controller needs to be shared between two subsystems.
>>
>> SE = Serial Engine, meant for I2C controller here.
>> TRE = Transfer Ring Element, refers to Queued Descriptor.
>> SS = Subsystems (APPS processor, Modem, TZ, ADSP etc).
>>
>> Example :
>> Two clients from different SS can share an I2C SE for same slave device
>> OR their owned slave devices.
>> Assume I2C Slave EEPROM device connected with I2C controller.
>> Each client from ADSP SS and APPS Linux SS can perform i2c transactions.
>> This gets serialized by lock TRE + DMA Transfers + Unlock TRE at HW level.
>>
>> Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
>> ---
>>   Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml b/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml
>> index 9f66a3bb1f80..3b9b20a0edff 100644
>> --- a/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml
>> +++ b/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml
>> @@ -60,6 +60,10 @@ properties:
>>     power-domains:
>>       maxItems: 1
>>   
>> +  qcom,shared-se:
>> +    description: True if I2C needs to be shared between two or more subsystems(SS).
> 
> The "SS" and subsystem should be explained in the binding. Please do not
> use some qcom-specific abbreviations here, but explain exactly, e.g.
> processors like application processor and DSP.
> 
> "se" is also not explained in the binding - please open it and look for
> such explanation.
Sure, i thought cover letter explanation is good enough. I will add it 
per patch as cover letter will not be visible and go away after merge.
> 
> This all should be rephrased to make it clear... We talked about this
> and I do not see much of improvements except commit msg, so we are
> making circles. I don't know, get someone internally to help you in
> upstreaming this.
Let me retry to make it better.
Will make SS (subsystem) to system processor (can be APPS or DSP OR any 
other).
> 
> Is sharing of IP blocks going to be also for other devices? If yes, then
> this should be one property for all Qualcomm devices. If not, then be
> sure that this is the case because I will bring it up if you come with
> one more solution for something else.
> 
IP blocks like SE can be shared. Here we are talking about I2C sharing.
In future it can be SPI sharing. But design wise it fits better to add 
flag per SE node. Same we shall be adding for SPI too in future.

Please let me know your further suggestions.
> Best regards,
> Krzysztof
>