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: <2ef6561c-d5ba-40d9-a085-fdced597233f@kernel.org>
Date: Mon, 27 Jan 2025 07:58:08 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Viken Dadhaniya <quic_vdadhani@...cinc.com>,
 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 24/01/2025 16:16, Viken Dadhaniya wrote:
> 
> 
> 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.

Well, no. Not 3 but 2, because why having gap there?

But anyway use string and explain what is GPI. I assume that DMA is
present in both cases, you just choose not to use it? If so, then why?

Best regards,
Krzysztof