In case of per port priority mapping, i don't know if this is working as
expected, as the IEEE priority mapping is done at ingress.
Eg. i think if MQPRIO channel mode is used to configure a pcp to queue mapping
on port 1 and a different mapping on port 2. Traffic received on port 1 that
gets forwarded to port 2 and egresses port 2 will end up in the queue
configured by the mapping on port 1. As mqprio is an egress qdisc, i don't
think that's expected.

Good point, it’s interesting there is egress mapping on the 6390 but only for FPri to DSCP. The Frame Priority Table set ordinal one would expect for egress QPri mapping is “reserved for future use”. (Be nice if it were an undocumented feature.)

I will remove the per-port mapping for the 6390 so all ports share the same mapping as they do on the 6352.

I have a patch that hasn't been submitted to the mailing list yet which
implements support for the dcb app pcp-prio command. This is also done by
configuring the IEEE priority mapping table.

Definitely happy to take a look if and when you submit, but I do plan to continue with this patch series (originally proposed as an RFC in September 2025).

Cheers,
Luke