Re: [PATCH v2 1/2] dt-bindings: ufs: Document static TX Equalization settings properties

[Can Guo <can.guo@oss.qualcomm.com>]

On 5/27/2026 5:15 PM, Manivannan Sadhasivam wrote:
> On Wed, May 27, 2026 at 04:51:04PM +0800, Can Guo wrote:
>> Hi Mani,
>>
>> On 5/23/2026 10:14 PM, Manivannan Sadhasivam wrote:
>>> On Sat, May 23, 2026 at 06:47:10AM -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 patternProperties:
>>>> txeq-settings-g[1-6]
>>>>
>>>> Each property is a uint32 array of per-lane tuples:
>>>> (PreShoot, DeEmphasis, PrecodeEn)
>>>>
>>> I don't think combining all EQ settings (PreShoot, DeEmphasis, PrecodeEn) in a
>>> single property as opaque tuples is the right approach. These are three
>>> semantically distinct parameters with independent value ranges. So packing
>>> them into a uint32 array makes validation impossible in the schema.
>>>
>>> AFACIS, PrecodeEn is applicable only to HS-G6 (PAM4), but the proposed
>>> patternProperties forces it into G1-G5 tuples as well, which is semantically
>>> wrong.
>> Point taken for the PrecodeEn.
>>> PCIe binding defines one property per data rate for EQ presets:
>>> https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/pci/pci-bus-common.yaml#L193
>>>
>>> Similarly, UFS should define one property per gear per (like, txeq-preshoot-g6,
>>> txeq-deemphasis-g6, txeq-precode-enable-g6,...) rather than clubbing everything
>>> into opaque tuples.
>> Thanks for the suggestion. I will go with below approach:
>>
>> txeq-preshoot-g6 = <Host Lane 0 PreShoot, Device Lane 0 PreShoot, Host Lane
>> 1 PreShoot, Device Lane 1 PreShoot>;
>> txeq-deemphasis-g6 = <Host Lane 0 DeEmphasis, Device Lane 0 DeEmphasis, Host
>> Lane 1 DeEmphasis, Device Lane 1 DeEmphasis>;
>> txeq-precode-en-g6 = <Host Lane 0 PrecodeEn, Device Lane 0 PrecodeEn, Host
>> Lane 1 PrecodeEn, Device Lane 1 PrecodeEn>;
>>
> How about encoding Host and Device values in a single tuple. Like,
>
> 	txeq-preshoot-g6 = <Lane_0 Host_PreShoot Device_PreShoot>, <Lane 1...>,
Man, I don't like that way to be honest, it took me a few minutes to 
understand it on the PCIe side...

Let's go with my approach please...

Thanks,
Can Guo.
>
> - Mani
>