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

[Marek Vasut]

On Monday, February 09, 2015 at 10:31:42 PM, Vince Bridgers wrote:
> Hi Marek!

Hi Vince!

> > We already do this kind of a programming in
> > board/altera/socfpga/socfpga.c in board_phy_config(), don't we ?
> 
> Yes, good point. This patch series is a first in some upcoming patches to
> make this better. The Linux implementation uses devicetree settings to set
> the skews, so if we were to follow that same model the code in socfpga.c
> would become deprecated in favor of setting the skews through the phy
> driver and subsequently removed. That way other users could take advantage
> of this through devicetree.

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

> The other problem with the current
> implementation is the skew values are part specific - we set the actual
> register values in the environment when it would be better to use a skewed
> time value (in +/- picoseconds).

You mean they are specific for particular PHY model ? Or board model ? Or
even particular board itself ?

> > Also, see [1], once I apply this, the DT support (not DM) for SoCFPGA
> > will become mandatory. Won't it make more sense to pull these values
> > from the DT instead of poluting the board environment with those please
> > ?
> 
> I agree it would make more sense to pull these from devicetree - I'm
> planning on adding that in a future patch. I thought it would be a good
> idea to pull these values from the environment first, overriding the
> devicetree (if present in the environment). This approach is helpful
> during bringup & debug since it doesn't require one to change the
> devicetree to try something quickly. I'm ok with any approach you think
> would work for the community.

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

> I'm ok with whatever the community decides considering my rationale above.

+CC Stefan and Pavel, please comment.

Best regards,
Marek Vasut