linux-kernel - Re: [PATCH v5 1/4] dt-bindindgs: i2c: qcom,i2c-geni: Document shared flag

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Message-ID: <c870f63a-3beb-4364-a993-880736d4bbe0@quicinc.com>
Date: Mon, 2 Dec 2024 16:08:32 +0530
From: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
To: Bjorn Andersson <andersson@...nel.org>
CC: <konrad.dybcio@...aro.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>, <quic_vdadhani@...cinc.com>
Subject: Re: [PATCH v5 1/4] dt-bindindgs: i2c: qcom,i2c-geni: Document shared
 flag

Hi Bjorn, Thanks for the review !

On 11/30/2024 10:15 AM, Bjorn Andersson wrote:
> On Fri, Nov 29, 2024 at 08:13:54PM +0530, Mukesh Kumar Savaliya wrote:
>> Adds qcom,shared-se flag usage. Use this flag when I2C serial controller
>> needs to be shared in multiprocessor system(APPS,Modem,ADSP) environment.
>>
> 
> Per https://docs.kernel.org/process/submitting-patches.html#describe-your-changes
> your commit message should start with a description of your problem.
> "Add" isn't the right word to start a problem description with.
Problem statement i have explained in cover letter, let me add here too 
in V6. I thought same story gets repeated here. Will not start with Add, 
but problem statement and need of this flag.
>> SE(Serial Engine HW controller acting as protocol master controller) is an
>> I2C controller. Basically a programmable SERDES(serializer/deserializer)
> 
> "Basically"?
will remove this.
> 
>> coupled with data DMA entity, capable in handling a bus protocol, and data
>> moves to/from system memory.
>>
>> Two clients from different processors can share an I2C controller 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.
>>
> 
> The DeviceTree binding describes properties used to describe the
> hardware; your commit message describes what a SE is and that it can
> exist can exist in a configuration with multiple client etc etc.
> 
I have explained the use of flag, and background surrounding to the 
feature. See the V4 and V5 and earlier, where i was required to explain 
and open up about "what is SE" ?
Because of the SE word in flag name, i had to expand with explanation.
>> Transfer gets serialized by Lock TRE + DMA xfer + Unlock TRE at HW level.
>>
> 
> This isn't what this patch implements. It defines a property which when
> specified means to the OS that any DMA transfers should be performed
> using TRE lock/unlock operations.
I agree, it adds onto understanding about the flag feature. I can remove 
this statement in V6. Let me get complete agreement.
> 
>> Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
>> ---
>>   .../devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml       | 8 ++++++++
>>   1 file changed, 8 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..88682a333399 100644
>> --- a/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml
>> +++ b/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml
>> @@ -60,6 +60,14 @@ properties:
>>     power-domains:
>>       maxItems: 1
>>   
>> +  qcom,shared-se:
>> +    description: True if I2C controller is shared between two or more system processors.
> 
> This attempts to describe the property.
I agree, thats why i limited but there was an ask to understand what is 
SE ? hence i added below.
> 
>> +        SE(Serial Engine HW controller working as protocol master controller) is an
>> +        I2C controller. Basically, a programmable SERDES(serializer/deserializer)
>> +        coupled with data DMA entity, capable in handling a bus protocol, and data
>> +        moves to/from system memory.
> 
> But this is basically just 4 lines of text expanding the acronym "se",
> but while it might give some insight into what this binding (the whole
> binding) is about, I'm afraid it doesn't add value to the understanding
> of the property...
> 
""se" is also not explained in the binding - please open it and look for
such explanation."

It was required to explain based on comment on V4, V5 hence i did. 
Please let me know if one line is enough to explain flag usage OR we 
need exact description from the hardware programming guide ?

I will need to get agreement on this patch first and then upload V6.

> Regards,
> Bjorn
> 
>> +    type: boolean
>> +
>>     reg:
>>       maxItems: 1
>>   
>> -- 
>> 2.25.1
>>