Spectrum ASICs have a configurable limit on how deep into the packet
they parse. By default, the limit is 96 bytes.

There are several cases where this parsing depth is not enough and there
is a need to increase it. For example, timestamping of PTP packets and a
FIB multipath hash policy that requires hashing on inner fields. The
driver therefore maintains a reference count that reflects the number of
consumers that require an increased parsing depth.

During reload_down() the parsing depth reference count does not
necessarily drop to zero, but the parsing depth itself is restored to
the default during reload_up() when the firmware is reset. It is
therefore possible to end up in situations where the driver thinks that
the parsing depth was increased (reference count is non-zero), when it
is not.

Fix by making sure that all the consumers that increase the parsing
depth reference count also decrease it during reload_down().
Specifically, make sure that when the routing code is de-initialized it
drops the reference count if it was increased because of a FIB multipath
hash policy that requires hashing on inner fields.

Add a warning if the reference count is not zero after the driver was
de-initialized and explicitly reset it to zero during initialization for
good measures.

Fixes: 2d91f080 ("mlxsw: spectrum: Add infrastructure for parsing configuration")
Reported-by: Maksym Yaremchuk <maksymy@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Link: https://lore.kernel.org/r/9c35e1b3e6c1d8f319a2449d14e2b86373f3b3ba.1678727526.git.petrm@nvidia.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>