linux-kernel - Re: [PATCH v2 2/8] dt-bindings: i2c: qcom,i2c-geni: Add support for selecting data transfer mode

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Message-ID: <da7b9678-76cc-4e45-89e9-4e8d9c9a2005@quicinc.com>
Date: Fri, 24 Jan 2025 17:52:24 +0530
From: Viken Dadhaniya <quic_vdadhani@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: <andi.shyti@...nel.org>, <robh@...nel.org>, <krzk+dt@...nel.org>,
        <conor+dt@...nel.org>, <gregkh@...uxfoundation.org>,
        <jirislaby@...nel.org>, <broonie@...nel.or>, <andersson@...nel.org>,
        <konradybcio@...nel.org>, <johan+linaro@...nel.org>,
        <dianders@...omium.org>, <agross@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-serial@...r.kernel.org>, <linux-spi@...r.kernel.org>,
        <quic_msavaliy@...cinc.com>, <quic_anupkulk@...cinc.com>
Subject: Re: [PATCH v2 2/8] dt-bindings: i2c: qcom,i2c-geni: Add support for
 selecting data transfer mode



On 1/24/2025 4:48 PM, Dmitry Baryshkov wrote:
> On Fri, Jan 24, 2025 at 04:23:03PM +0530, Viken Dadhaniya wrote:
>> Data transfer mode is fixed by TrustZone (TZ), which currently restricts
>> developers from modifying the transfer mode from the APPS side.
>>
>> Document the 'qcom,xfer-mode' properties to select the data transfer mode,
>> either GPI DMA (Generic Packet Interface) or non-GPI mode (PIO/CPU DMA).
>>
>> I2C controller can operate in one of two modes based on the
>> 'qcom,xfer-mode' property, and the firmware is loaded accordingly.
> 
> Is it possible to load the firmware after it being loaded by TZ? Is it
> possible to change the mode at runtime too?

No, firmware can be loaded either from the TZ side or APPS side.

In non-GPI mode, the transfer mode will change runtime between PIO and 
CPU DMA based on the data length.

We need to update the device tree property(qcom,xfer-mode) to change the 
mode between non-GPI and GPI.

> 
>>
>> Co-developed-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
>> Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
>> Signed-off-by: Viken Dadhaniya <quic_vdadhani@...cinc.com>
>> ---
>>
>> v1 -> v2:
>>
>> - Drop 'qcom,load-firmware' property and add 'firmware-name' property in
>>    qup common driver.
>> - Update commit log.
>>
>> v1 Link: https://lore.kernel.org/linux-kernel/20241204150326.1470749-2-quic_vdadhani@quicinc.com/
>> ---
>> ---
>>   .../devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml        | 7 +++++++
>>   1 file changed, 7 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..68e4bf0c84d1 100644
>> --- a/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml
>> +++ b/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml
>> @@ -66,6 +66,12 @@ properties:
>>     required-opps:
>>       maxItems: 1
>>   
>> +  qcom,xfer-mode:
>> +    description: Set the value to 1 for non-GPI (FIFO/CPU DMA) mode and 3 for GPI DMA mode.
>> +      The default mode is FIFO.
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    enum: [1, 3]
>> +
>>   required:
>>     - compatible
>>     - interrupts
>> @@ -142,5 +148,6 @@ examples:
>>           interconnect-names = "qup-core", "qup-config", "qup-memory";
>>           power-domains = <&rpmhpd SC7180_CX>;
>>           required-opps = <&rpmhpd_opp_low_svs>;
>> +        qcom,xfer-mode = <1>;
> 
> What does <1> mean? Please provide corresponding defines.

Do we need to add a string instead of a number, like 
include/dt-bindings/dma/qcom-gpi.h?

> 
>>       };
>>   ...
>> -- 
>> 2.34.1
>>
>