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