[U-Boot] [PATCH 2/2] net: phy: Add ability to program the ksz9031 skew values from the uboot env

Vince Bridgers
2015-02-13T16:05:43Z

Hi Stefan

> >
> > Setting the skews in DT would indeed be preferable in my opinion.

> +1 from me.

Agreed. I'll focus on a devicetree based implementation, and editing phy values during board debug and bringup can be addressed with debug/development notes. I'd be willing to publish these somewhere with some suggestions about the best place for something like this to reside based on our experience.

> >
> > You can do that with the 'mii' command as well I think, but I might be wrong.

> Yes. For testing or board bringup this might really serve. Even though
> this setting via environment as proposed from Vince is more elegant and
> less hackish. And easier to adjust/tune for "normal users".

This was the intent of having environment variables - to make trying different skew values easy for our customers. Not all developers/users are Uboot experts and need help from time to time. I think this can also be addressed by writing use case notes on how to edit phy registers using the mii command for debug/bringup purposes.

> The default values should come from the DT, once this is all in place.
> But I think that for initial board bringup / testing such a method, to
> override those values via environment variables can be quite helpful.

After reading through most of the comments, I agree with Marek it's possible (and probably best) to support overriding phy registers through use of the mii command. Non expert users (such as hardware developers bringing up a new board) could make use of notes to help them know how to try different settings.

All the best!

Vince