net: mscc: ocelot: convert to phylink

The felix DSA driver, which is a wrapper over the same hardware class as
ocelot, is integrated with phylink, but ocelot is using the plain PHY
library. It makes sense to bring together the two implementations, which
is what this patch achieves.

This is a large patch and hard to break up, but it does the following:

The existing ocelot_adjust_link writes some registers, and
felix_phylink_mac_link_up writes some registers, some of them are
common, but both functions write to some registers to which the other
doesn't.

The main reasons for this are:
- Felix switches so far have used an NXP PCS so they had no need to
  write the PCS1G registers that ocelot_adjust_link writes
- Felix switches have the MAC fixed at 1G, so some of the MAC speed
  changes actually break the link and must be avoided.

The naming conventions for the functions introduced in this patch are:
- vsc7514_phylink_{mac_config,validate} are specific to the Ocelot
  instantiations and placed in ocelot_net.c which is built only for the
  ocelot switchdev driver.
- ocelot_phylink_mac_link_{up,down} are shared between the ocelot
  switchdev driver and the felix DSA driver (they are put in the common
  lib).

One by one, the registers written by ocelot_adjust_link are:

DEV_MAC_MODE_CFG - felix_phylink_mac_link_up had no need to write this
                   register since its out-of-reset value was fine and
                   did not need changing. The write is moved to the
                   common ocelot_phylink_mac_link_up and on felix it is
                   guarded by a quirk bit that makes the written value
                   identical with the out-of-reset one
DEV_PORT_MISC - runtime invariant, was moved to vsc7514_phylink_mac_config
PCS1G_MODE_CFG - same as above
PCS1G_SD_CFG - same as above
PCS1G_CFG - same as above
PCS1G_ANEG_CFG - same as above
PCS1G_LB_CFG - same as above
DEV_MAC_ENA_CFG - both ocelot_adjust_link and ocelot_port_disable
                  touched this. felix_phylink_mac_link_{up,down} also
                  do. We go with what felix does and put it in
                  ocelot_phylink_mac_link_up.
DEV_CLOCK_CFG - ocelot_adjust_link and felix_phylink_mac_link_up both
                write this, but to different values. Move to the common
                ocelot_phylink_mac_link_up and make sure via the quirk
                that the old values are preserved for both.
ANA_PFC_PFC_CFG - ocelot_adjust_link wrote this, felix_phylink_mac_link_up
                  did not. Runtime invariant, speed does not matter since
                  PFC is disabled via the RX_PFC_ENA bits which are cleared.
                  Move to vsc7514_phylink_mac_config.
QSYS_SWITCH_PORT_MODE_PORT_ENA - both ocelot_adjust_link and
                                 felix_phylink_mac_link_{up,down} wrote
                                 this. Ocelot also wrote this register
                                 from ocelot_port_disable. Keep what
                                 felix did, move in ocelot_phylink_mac_link_{up,down}
                                 and delete ocelot_port_disable.
ANA_POL_FLOWC - same as above
SYS_MAC_FC_CFG - same as above, except slight behavior change. Whereas
                 ocelot always enabled RX and TX flow control, felix
                 listened to phylink (for the most part, at least - see
                 the 2500base-X comment).

The registers which only felix_phylink_mac_link_up wrote are:

SYS_PAUSE_CFG_PAUSE_ENA - this is why I am not sure that flow control
                          worked on ocelot. Not it should, since the
                          code is shared with felix where it does.
ANA_PORT_PORT_CFG - this is a Frame Analyzer block register, phylink
                    should be the one touching them, deleted.

Other changes:

- The old phylib registration code was in mscc_ocelot_init_ports. It is
  hard to work with 2 levels of indentation already in, and with hard to
  follow teardown logic. The new phylink registration code was moved
  inside ocelot_probe_port(), right between alloc_etherdev() and
  register_netdev(). It could not be done before (=> outside of)
  ocelot_probe_port() because ocelot_probe_port() allocates the struct
  ocelot_port which we then use to assign ocelot_port->phy_mode to. It
  is more preferable to me to have all PHY handling logic inside the
  same function.
- On the same topic: struct ocelot_port_private :: serdes is only used
  in ocelot_port_open to set the SERDES protocol to Ethernet. This is
  logically a runtime invariant and can be done just once, when the port
  registers with phylink. We therefore don't even need to keep the
  serdes reference inside struct ocelot_port_private, or to use the devm
  variant of of_phy_get().
- Phylink needs a valid phy-mode for phylink_create() to succeed, and
  the existing device tree bindings in arch/mips/boot/dts/mscc/ocelot_pcb120.dts
  don't define one for the internal PHY ports. So we patch
  PHY_INTERFACE_MODE_NA into PHY_INTERFACE_MODE_INTERNAL.
- There was a strategically placed:

	switch (priv->phy_mode) {
	case PHY_INTERFACE_MODE_NA:
	        continue;

  which made the code skip the serdes initialization for the internal
  PHY ports. Frankly that is not all that obvious, so now we explicitly
  initialize the serdes under an "if" condition and not rely on code
  jumps, so everything is clearer.
- There was a write of OCELOT_SPEED_1000 to DEV_CLOCK_CFG for QSGMII
  ports. Since that is in fact the default value for the register field
  DEV_CLOCK_CFG_LINK_SPEED, I can only guess the intention was to clear
  the adjacent fields, MAC_TX_RST and MAC_RX_RST, aka take the port out
  of reset, which does match the comment. I don't even want to know why
  this code is placed there, but if there is indeed an issue that all
  ports that share a QSGMII lane must all be up, then this logic is
  already buggy, since mscc_ocelot_init_ports iterates using
  for_each_available_child_of_node, so nobody prevents the user from
  putting a 'status = "disabled";' for some QSGMII ports which would
  break the driver's assumption.
  In any case, in the eventuality that I'm right, we would have yet
  another issue if ocelot_phylink_mac_link_down would reset those ports
  and that would be forbidden, so since the ocelot_adjust_link logic did
  not do that (maybe for a reason), add another quirk to preserve the
  old logic.

The ocelot driver teardown goes through all ports in one fell swoop.
When initialization of one port fails, the ocelot->ports[port] pointer
for that is reset to NULL, and teardown is done only for non-NULL ports,
so there is no reason to do partial teardowns, let the central
mscc_ocelot_release_ports() do its job.

Tested bind, unbind, rebind, link up, link down, speed change on mock-up
hardware (modified the driver to probe on Felix VSC9959). Also
regression tested the felix DSA driver. Could not test the Ocelot
specific bits (PCS1G, SERDES, device tree bindings).

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>