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

[Can Guo]

On 5/31/2026 9:41 AM, Can Guo wrote:
> On 5/31/2026 1:33 AM, Krzysztof Kozlowski wrote:
> > 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 <mani@xxxxxxxxxx>
> > > > > Reviewed-by: Bean Huo <beanhuo@xxxxxxxxxx>
> > > > > Reviewed-by: Peter Wang <peter.wang@xxxxxxxxxxxx>
> > > > > Signed-off-by: Can Guo <can.guo@xxxxxxxxxxxxxxxx>
> > > > > ---
> > > > >    .../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.
> Thanks for the clarification. Will do.
> > > 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'?
> The tuple is still needed because Precoding is configured per 
> transmitter-receiver pair,
> so each lane has two independent states:
> - Host_TX -> Device_RX
> - Device_TX -> Host_RX
> A lane-only enabled list cannot represent directional combinations 
> like lane0 =
> (on, off) vs (off, on).
How about we split into two properties, something like below?
tx-precode-enable-g6-host-lanes = <0 1>
tx-precode-enable-g6-device-lanes = <1>

Only listed lanes are enabled; unlisted lanes are disabled by default.

Are you OK with this approach?

Thanks,
Can Guo.
> > > 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.
> I will keep the per-lane tuple model but switch tx-precode-enable-g6 
> from 0/1 to
> "on"/"off" (string array) in v7.
>
> Thanks,
> Can Guo.
> > Best regards,
> > Krzysztof