Subject: Re: [PATCH v6 1/2] dt-bindings: ufs: Document static TX Equalization settings properties

From: Krzysztof Kozlowski <[email-masked]>
Date: Fri, 29 May 2026 18:58:24 +0200

On Fri, May 29, 2026 at 04:33:37AM -0700, Can Guo wrote:
> UFS v5.0/UFSHCI v5.0 add HS-G6 support (46.6 Gbps/lane) via UniPro v3.0
> and M-PHY v6.0. In these specs, TX Equalization is defined for all High
> Speed Gears (not only HS-G6) to compensate channel loss and improve signal
> integrity at high speed operation.
> 
> For HS-G6, M-PHY uses PAM4 1b1b line coding, Pre-Coding may also be
> required depending on channel characteristics.
> 
> Add vendor-neutral DT properties:
> 
> - patternProperties for txeq-preshoot-g[1-6] and txeq-deemphasis-g[1-6]
> - fixed property tx-precode-enable-g6
> 
> Each property is a uint32 array of per-lane tuples:
> <Host_Lane0 Device_Lane0>, [<Host_Lane1 Device_Lane1>]
> 
> Accept 2 or 4 values (x1/x2 lane configs). PreShoot and DeEmphasis values
> are 0..7. Precode enable values are 0/1 and only applicable to HS-G6.
> 
> Acked-by: Manivannan Sadhasivam <[email-masked]>
> Reviewed-by: Bean Huo <[email-masked]>
> Reviewed-by: Peter Wang <[email-masked]>
> Signed-off-by: Can Guo <[email-masked]>
> ---
>  .../devicetree/bindings/ufs/ufs-common.yaml   | 45 +++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/ufs/ufs-common.yaml b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
> index ed97f5682509..d90cf25adfa5 100644
> --- a/Documentation/devicetree/bindings/ufs/ufs-common.yaml
> +++ b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
> @@ -105,6 +105,51 @@ 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-array
> +    oneOf:
> +      - minItems: 2
> +        maxItems: 2
> +      - minItems: 4
> +        maxItems: 4
> +    items:
> +      enum: [0, 1]
> +    description: |
> +      Static TX Precode enable values for HS-G6 only.
> +      Values are specified as per-lane tuples:
> +      <Host_Lane0 Device_Lane0>, [<Host_Lane1 Device_Lane1>].

You need to include them in any of applicable examples, otherwise
nothing here is validated.

Why values cannot be on or off? Or even better: why you cannot just list
all the lanes which has it enabled, assuming disabled is by default?

> +
> +patternProperties:
> +  "^txeq-preshoot-g[1-6]$":
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +    oneOf:
> +      - minItems: 2
> +        maxItems: 2
> +      - minItems: 4
> +        maxItems: 4
> +    items:
> +      minimum: 0
> +      maximum: 7

What is the meaning of values? Nothing here refers to the spec, so is
this driver specific?

Best regards,
Krzysztof