Re: [PATCH v2 4/8] dt-bindings: serial: Add support for selecting data transfer mode

Krzysztof Kozlowski
2025-01-27T16:24:30Z

On 27/01/2025 15:27, Dmitry Baryshkov wrote:
> On Mon, Jan 27, 2025 at 08:02:12AM +0100, Krzysztof Kozlowski wrote:
>> On 24/01/2025 11:53, 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).
>>>
>>> UART controller can operate in one of two modes based on the
>>> 'qcom,xfer-mode' property, and the firmware is loaded accordingly.
>>>
>>> Co-developed-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
>>> Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
>>> Signed-off-by: Viken Dadhaniya <quic_vdadhani@quicinc.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/20241204150326.1470749-4-quic_vdadhani@quicinc.com/
>>> ---
>>> ---
>>> .../devicetree/bindings/serial/qcom,serial-geni-qcom.yaml | 8 ++++++++
>>> 1 file changed, 8 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/serial/qcom,serial-geni-qcom.yaml b/Documentation/devicetree/bindings/serial/qcom,serial-geni-qcom.yaml
>>> index dd33794b3534..383773b32e47 100644
>>> --- a/Documentation/devicetree/bindings/serial/qcom,serial-geni-qcom.yaml
>>> +++ b/Documentation/devicetree/bindings/serial/qcom,serial-geni-qcom.yaml
>>> @@ -56,6 +56,13 @@ properties:
>>> reg:
>>> 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]
>>> +
>>> +
>>
>> Just one blank line, but anyway, this property should not be in three
>> places. Do you really expect that each of serial engines within one
>> GeniQUP will be configured differently by TZ?
>
> Yes, each SE is configured separately and it's quite frequent when
> different SEs have different DMA configuration.

Well, I checked at sm8550 and sm8650 and each pair of SE - which shares
resources - has the same DMAs, so I would not call it frequent. Care to
bring an example where same serial engines have different DMAs and
different TZ? We do not talk about single QUP.

Anyway, if you need property per node, this has to be shared schema.

Best regards,
Krzysztof