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

From: Krzysztof Kozlowski <[email-masked]>
Date: Sat, 30 May 2026 19:33:20 +0200

On 30/05/2026 14:45, Can Guo wrote:
> 
> 
> On 5/30/2026 12:58 AM, Krzysztof Kozlowski wrote:
>> 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.
> Hi Krzysztof,
> 
> Thanks for the review.
> 
> Since no UFS5-capable SoC binding exists upstream yet (the target SoC is

I would imagine cover letter or commit msg would briefly mention that.

> still pre-CS), there is no vendor-specific YAML to attach the example to.
> 
> Is a synthetic example directly in ufs-common.yaml OK to you?

Skip example in such case.

>>
>> 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?
> Thanks for the suggestions.
> 
> For the "just list enabled lanes" suggestion: precode must be configured
> independently for the Host-side TX and Device-side TX transceivers within
> the same physical lane. A lane index list alone cannot capture this
> two-dimensional per-lane state. The tuple format <Host_LaneN Device_LaneN>
> is the minimal encoding that covers both.

Again, why do you need to encode '0'?

> 
> For the "on/off" suggestion: the on/off string pattern is used with
> single-value properties (e.g. LED default-state) read via
> of_property_read_string(). I am not aware of precedent for on/off as a
> string array for per-lane tuples.

git grep string-array. Plenty of precedents.

Best regards,
Krzysztof