On 11.02.2015 09:07, Joe Hershberger wrote:
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.
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".
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.
Joe, whats your opinion on this?
Do we really think this is a strong use-case? This seem like the type of thing I would expect to tweak for testing through mii / mdio commands and then configure the device tree based on that. This is pretty much a one-time thing for a given board it seems to me.
If we really want a polished interface to it, we should define a sub-command / new command that phy drivers can implement. I'm not sure an undiscoverable, un-"help"-able list of env vars will be apparent to users. Do you have a feeling for how close to universal any of these parameters are across phys?
No. But with your comments above (which make total sense), I tend to NAK this ability to configure the PHY skew timings via environment variables.
Thanks, Stefan