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: <38d24c6b-369e-4254-ae50-5387e2b6063e@quicinc.com>
Date: Fri, 24 Jan 2025 20:46:39 +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 8:33 PM, Dmitry Baryshkov wrote:
> On Fri, Jan 24, 2025 at 05:52:24PM +0530, Viken Dadhaniya wrote:
>>
>>
>> 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.
> 
> You answer actually reads as "No, yes" (excuse me, non-native here).
> Most likely you mean that it can not be reloaded once either TZ or APPS
> has loaded it.

Yes correct. it can not be reloaded once either TZ or APPS has loaded it.

> 
>> 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.
> 
> So, is it actually possible to change the mode? E.g. if the TZ has
> loaded the firmware and configured SE for PIO/SE DMA, is it possible to
> change it to GPI DMA?

No, if the TZ has loaded the firmware, it is not possible to switch from 
non-GPI (PIO/SE DMA) to GPI DMA mode.

> 
>>
>>>
>>>>
>>>> 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?
> 
> You need to '#define FOO_BAR 1', then another one for 3. String is a
> "string", it's not required here (in my opinion).
> 

Sure, I will update it in the next patch.