Merge branch 'mlxsw-introduce-initial-xm-router-support'

Ido Schimmel says:

====================
mlxsw: Introduce initial XM router support

This patch set implements initial eXtended Mezzanine (XM) router
support.

The XM is an external device connected to the Spectrum-{2,3} ASICs using
dedicated Ethernet ports. Its purpose is to increase the number of
routes that can be offloaded to hardware. This is achieved by having the
ASIC act as a cache that refers cache misses to the XM where the FIB is
stored and LPM lookup is performed.

Future patch sets will add more sophisticated cache flushing and
selftests that utilize cache counters on the ASIC, which we plan to
expose via devlink-metric [1].

Patch set overview:

Patches #1-#2 add registers to insert/remove routes to/from the XM and
to enable/disable it. Patch #3 utilizes these registers in order to
implement XM-specific router low-level operations.

Patches #4-#5 query from firmware the availability of the XM and the
local ports that are used to connect the ASIC to the XM, so that netdevs
will not be created for them.

Patches #6-#8 initialize the XM by configuring its cache parameters.

Patch #9-#10 implement cache management, so that LPM lookup will be
correctly cached in the ASIC.

Patches #11-#13 implement cache flushing, so that routes
insertions/removals to/from the XM will flush the affected entries in
the cache.

Patch #14 configures the ASIC to allocate half of its memory for the
cache, so that room will be left for other entries (e.g., FDBs,
neighbours).

Patch #15 starts using the XM for IPv4 route offload, when available.

[1] https://lore.kernel.org/netdev/20200817125059.193242-1-idosch@idosch.org/
====================

Link: https://lore.kernel.org/r/20201214113041.2789043-1-idosch@idosch.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>