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

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Message-ID: <10060d39-87a4-4565-a2a6-80c93ac2266a@kernel.org>
Date: Mon, 27 Jan 2025 08:02:12 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Viken Dadhaniya <quic_vdadhani@...cinc.com>, 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
Cc: quic_msavaliy@...cinc.com, quic_anupkulk@...cinc.com
Subject: Re: [PATCH v2 4/8] dt-bindings: serial: Add support for selecting
 data transfer mode

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@...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/20241204150326.1470749-4-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?

Best regards,
Krzysztof