One last update on this:
There was an issue with our PHY where both of the PHYs were responding to packets set to PHY address 0. This is apparently known as "broadcast mode" and on these PHYs you have to turn it off. The CPSW switch wasn't active because the PHYs were returning a link state of 1 and 0, which apparently coalesced to a 0, making the switch think they were off.
I'm not sure why eth0 was reporting as "up" despite this.
After turning the broadcast mode off, the PHYs reported their proper status, the ethernet interface got an IP address, and ping began working. Thanks for all the help.