Re: [PATCH v8 1/2] dt-bindings: ufs: Document static TX Equalization settings properties

[Krzysztof Kozlowski <krzk@kernel.org>]

On 15/06/2026 10:50, Can Guo wrote:
> UFS v5.0/UFSHCI v5.0 adds HS-G6 support (46.6 Gbps/lane) via UniPro
> v3.0 and M-PHY v6.0. These specs define TX Equalization for all
> High-Speed Gears (not only HS-G6) to compensate channel loss and
> improve signal integrity at high speed.
> 
> For HS-G6, M-PHY uses PAM4 1b1b line coding. Pre-Coding may also be
> required depending on channel characteristics.
> 
> Document vendor-neutral properties in ufs-common.yaml:
> - txeq-preshoot-g[1-6]
> - txeq-deemphasis-g[1-6]
> - tx-precode-enable-g6
> 
> Values are per-lane Host/Device tuples (2 values for x1, 4 values for
> x2). PreShoot/DeEmphasis range from 0..7, and Precode is 0/1.
> 
> These are board-specific signal-integrity tuning values. They depend on
> channel SI/PHY characterization and validation (host PHY, device PHY,
> package, and board routing), and are determined by HW/PHY designers.
> 
> Although UFSHCI v5.0 supports TX Equalization Training via UniPro v3.0,
> which allows host software to determine optimal TX Equalization at
> runtime, static board-specific TX Equalization settings in the Device
> Tree are still necessary because:
> - TX Equalization Training is not supported for HS-G3 and below
> - TX Equalization Training is disabled on some platforms
> 
> Signed-off-by: Can Guo <can.guo@oss.qualcomm.com>
> ---
>  .../devicetree/bindings/ufs/ufs-common.yaml   | 55 +++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/ufs/ufs-common.yaml b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
> index ed97f5682509..145a6416e1df 100644
> --- a/Documentation/devicetree/bindings/ufs/ufs-common.yaml
> +++ b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
> @@ -105,6 +105,61 @@ properties:
>        Restricts the UFS controller to rate-a or rate-b for both TX and
>        RX directions.
>  
> +  tx-precode-enable-g6:
> +    $ref: /schemas/types.yaml#/definitions/uint32-matrix
> +    oneOf:
> +      - items:
> +          - description: Host_Lane0 precode
> +          - description: Device_Lane0 precode
> +      - items:
> +          - description: Host_Lane0 precode
> +          - description: Device_Lane0 precode
> +          - description: Host_Lane1 precode
> +          - description: Device_Lane1 precode
> +    items:
> +      enum: [0, 1]
> +    description:
> +      Static TX Precode enable values for HS-G6 only.

My bad here, that was my mistake. I wanted matrix, but gave you array
syntax. Proper code would be:

  tx-precode-enable-g6:
    $ref: /schemas/types.yaml#/definitions/uint32-matrix
    minItems: 1
    items:
      - items:
          - description: Host_Lane0 precode
            enum: [0, 1]
          - description: Device_Lane0 precode
            enum: [0, 1]
      - items:
          - description: Host_Lane1 precode
            enum: [0, 1]
          - description: Device_Lane1 precode
            enum: [0, 1]
    description:
      Static TX Precode enable values for HS-G6 only.


I tested it with DTS and seems to work fine. Please use the same for
other properties, but enum will be 0-7.


Best regards,
Krzysztof