Feature request: i2c/SMBus signals routed to M.2 connector

[jk-ozlabs]

Since there is the M.2 connector on the DC-SCM board, it would be nice to be able to perform out-of-band management of NVMe devices, using either the NVMe-MI or NVMe basic management protocols.

This would just be a matter of connecting the SMB_DATA (pin 42) and SMB_CLOCK (pin 40) signals of J2 to a couple of IO pins of the Artix. the SMBus alert signal shouldn't be needed for NVMe management.

The M.2 spec defines these as 1.8V signals, so they'd either need to go through a translator, or could we potentially use a separate Artix IO bank running at 1.8V?

We have implemented a bunch of NVMe-MI (over MCTP over i2c) infrastructure for existing BMCs already, and have it working with M.2 devices - would be useful to be able to do this on the DC-SCM board too.