Merge branch 'qca8k-mdio'

Ansuel Smith says:

====================
Add support for qca8k mdio rw in Ethernet packet

The main reason for this is that we notice some routing problem in the
switch and it seems assisted learning is needed. Considering mdio is
quite slow due to the indirect write using this Ethernet alternative way
seems to be quicker.

The qca8k switch supports a special way to pass mdio read/write request
using specially crafted Ethernet packet.
This works by putting some defined data in the Ethernet header where the
mac source and dst should be placed. The Ethernet type header is set to qca
header and is set to a mdio read/write type.
This is used to communicate to the switch that this is a special packet
and should be parsed differently.

Currently we use Ethernet packet for
- MIB counter
- mdio read/write configuration
- phy read/write for each port

Current implementation of this use completion API to wait for the packet
to be processed by the tagger and has a timeout that fallback to the
legacy mdio way and mutex to enforce one transaction at time.

We now have connect()/disconnect() ops for the tagger. They are used to
allocate priv data in the dsa priv. The header still has to be put in
global include to make it usable by a dsa driver.
They are called when the tag is connect to the dst and the data is freed
using discconect on tagger change.

(if someone wonder why the bind function is put at in the general setup
function it's because tag is set in the cpu port where the notifier is
still not available and we require the notifier to sen the
tag_proto_connect() event.

We now have a tag_proto_connect() for the dsa driver used to put
additional data in the tagger priv (that is actually the dsa priv).
This is called using a switch event DSA_NOTIFIER_TAG_PROTO_CONNECT.
Current use for this is adding handler for the Ethernet packet to keep
the tagger code as dumb as possible.

The tagger priv implement only the handler for the special packet. All the
other stuff is placed in the qca8k_priv and the tagger has to access
it under lock.

We use the new API from Vladimir to track if the master port is
operational or not. We had to track many thing to reach a usable state.
Checking if the port is UP is not enough and tracking a NETDEV_CHANGE is
also not enough since it use also for other task. The correct way was
both track for interface UP and if a qdisc was assigned to the
interface. That tells us the port (and the tagger indirectly) is ready
to accept and process packet.

I tested this with multicpu port and with port6 set as the unique port and
it's sad.
It seems they implemented this feature in a bad way and this is only
supported with cpu port0. When cpu port6 is the unique port, the switch
doesn't send ack packet. With multicpu port, packet ack are not duplicated
and only cpu port0 sends them. This is the same for the MIB counter.
For this reason this feature is enabled only when cpu port0 is enabled and
operational.

v8:
- Reworked to rolling counter for the seq_num
- Reworked the hi/lo cache patch
- Fix multiple missing skb free and mutex lock errors
- Fix some spelling mistake
- Add macro build check for mgmt packet size
- Change some struct naming to make them more descriptive
v7:
- Rebase on net-next changes
- Add bulk patches to speedup this even more
v6:
- Fix some error in ethtool handler caused by rebase/cleanup
v5:
- Adapt to new API fixes
- Fix a wrong logic for noop
- Add additional lock for master_state change
- Limit mdio Ethernet to cpu port0 (switch limitation)
- Add priority to these special packet
- Move mdio cache to qca8k_priv
v4:
- Remove duplicate patch sent by mistake.
v3:
- Include MIB with Ethernet packet.
- Include phy read/write with Ethernet packet.
- Reorganize code with new API.
- Introuce master tracking by Vladimir
v2:
- Address all suggestion from Vladimir.
  Try to generilize this with connect/disconnect function from the
  tagger and tag_proto_connect for the driver.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

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