Re: [PATCH 1/3] dt-bindings: dsa: microchip: add KSZ low-loss cable errata properties

[Andrew Lunn]

On Thu, Mar 26, 2026 at 10:10:21AM +0100, Fidelio Lawson wrote:
> Microchip KSZ87xx switches are affected by the "Module 3: Equalizer fix
> for short cables" erratum described in DS80000687C.
> The embedded PHY receivers are tuned for long, high-loss cables,
> which may cause signal distortion when operated with short or low-loss
> cabling such as CAT5e or CAT6. In these cases,
> the PHY may fail to establish a link due to internal over-amplification.
> 
> Two workarounds are provided by Microchip, each configuring a different
> indirect register value to adjust the PHY equalizer settings.
> 
> This patch introduces two new device tree properties to enable and
> select the appropriate workaround:
> 
>   - microchip,low-loss-errata-enable: boolean enabling the feature
>   - microchip,low-loss-errata: selects workaround 1 or 2 (default: 1)
> 
> These properties allow board designers to opt into the errata fix
> according to the targeted cable characteristics of their platform.

Does the errata give any indication how the two different workarounds
differ? How would a user decided which to use?

I also question if this should be a DT property. The length of the
cables is not a property of the board.

A PHY tunable would better reflect the same board can be used with
different cables, with different lengths/quality.

	  Andrew