net: dsa: mv88e6xxx: Fix mv88e6352_serdes_get_stats error path

mv88e6xxx_get_stats, which collects stats from various sources,
expects all callees to return the number of stats read. If an error
occurs, 0 should be returned.

Prevent future mishaps of this kind by updating the return type to
reflect this contract.

Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: cleanup after phylink_pcs conversion

Now that mv88e6xxx is completely converted to using phylink_pcs
support, we have no need for the serdes methods. Remove all this
infrastructure. Also remove the __maybe_unused from
mv88e6xxx_pcs_select().

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: convert 88e639x to phylink_pcs

Convert the 88E6390, 88E6390X, and 88E6393X family of switches to use
the phylink_pcs infrastructure.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: convert 88e6352 to phylink_pcs

Convert the 88E6352 SERDES code to use the phylink_pcs infrastructure.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: convert 88e6185 to phylink_pcs

Convert the 88E6185 SERDES code to use the phylink_pcs infrastructure.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: export mv88e6xxx_pcs_decode_state()

Rename and export the PCS state decoding function so our PCS can
make use of the functionality provided by this.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: implement USXGMII mode for mv88e6393x

Enable USXGMII mode for mv88e6393x chips. Tested on Marvell 88E6191X.

Signed-off-by: Michal Smulski <michal.smulski@ooma.com>
Link: https://lore.kernel.org/r/20230605174442.12493-1-msmulski2@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

dsa: mv88e6xxx: make serdes SGMII/Fiber tx amplitude configurable

The mv88e6352, mv88e6240 and mv88e6176 have a serdes interface. This patch
allows to configure the output swing to a desired value in the
phy-handle of the port. The value which is peak to peak has to be
specified in microvolts. As the chips only supports eight dedicated
values we return EINVAL if the value in the DTS does not match one of
these values.

Signed-off-by: Holger Brunck <holger.brunck@hitachienergy.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Marek Behún <kabel@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Fix inband AN for 2500base-x on 88E6393X family

Inband AN is broken on Amethyst in 2500base-x mode when set by standard
mechanism (via cmode).

(There probably is some weird setting done by default in the switch for
this mode that make it cycle in some state or something, because when
the peer is the mvneta controller, it receives link change interrupts
every ~0.3ms, but the link is always down.)

Get around this by configuring the PCS mode to 1000base-x (where inband
AN works), and then changing the SerDes frequency while SerDes
transmitter and receiver are disabled, before enabling SerDes PHY. After
disabling SerDes PHY, change the PCS mode back to 2500base-x, to avoid
confusing the device (if we leave it at 1000base-x PCS mode but with
different frequency, and then change cmode to sgmii, the device won't
change the frequency because it thinks it already has the correct one).

The register which changes the frequency is undocumented. I discovered
it by going through all registers in the ranges 4.f000-4.f100 and
1e.8000-1e.8200 for all SerDes cmodes (sgmii, 1000base-x, 2500base-x,
5gbase-r, 10gbase-r, usxgmii) and filtering out registers that didn't
make sense (the value was the same for modes which have different
frequency). The result of this was:

reg sgmii 1000base-x 2500base-x 5gbase-r 10gbase-r usxgmii
04.f002 005b 0058 0059 005c 005d 005f
04.f076 3000 0000 1000 4000 5000 7000
04.f07c 0950 0950 1850 0550 0150 0150
1e.8000 0059 0059 0058 0055 0051 0051
1e.8140 0e20 0e20 0e28 0e21 0e42 0e42

Register 04.f002 is the documented Port Operational Confiuration
register, it's last 3 bits select PCS type, so changing this register
also changes the frequency to the appropriate value.

Registers 04.f076 and 04.f07c are not writable.

Undocumented register 1e.8000 was the one: changing bits 3:0 from 9 to 8
changed SerDes frequency to 3.125 GHz, while leaving the value of PCS
mode in register 04.f002.2:0 at 1000base-x. Inband autonegotiation
started working correctly.

(I didn't try anything with register 1e.8140 since 1e.8000 solved the
problem.)

Since I don't have documentation for this register 1e.8000.3:0, I am
using the constants without names, but my hypothesis is that this
register selects PHY frequency. If in the future I have access to an
oscilloscope able to handle these frequencies, I will try to test this
hypothesis.

Fixes: de776d0d316f ("net: dsa: mv88e6xxx: add support for mv88e6393x family")
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Save power by disabling SerDes trasmitter and receiver

Save power on 88E6393X by disabling SerDes receiver and transmitter
after SerDes is SerDes is disabled.

Signed-off-by: Marek Behún <kabel@kernel.org>
Cc: stable@vger.kernel.org # de776d0d316f ("net: dsa: mv88e6xxx: add support for mv88e6393x family")
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: add support for mv88e6393x family

The Marvell 88E6393X device is a single-chip integration of a 11-port
Ethernet switch with eight integrated Gigabit Ethernet (GbE)
transceivers and three 10-Gigabit interfaces.

This patch adds functionalities specific to mv88e6393x family (88E6393X,
88E6193X and 88E6191X).

The main differences between previous devices and this one are:
- port 0 can be a SERDES port
- all SERDESes are one-lane, eg. no XAUI nor RXAUI
- on the other hand the SERDESes can do USXGMII, 10GBASER and 5GBASER
(on 6191X only one SERDES is capable of more than 1g; USXGMII is not
yet supported with this change)
- Port Policy CTL register is changed to Port Policy MGMT CTL register,
via which several more registers can be accessed indirectly
- egress monitor port is configured differently
- ingress monitor/CPU/mirror ports are configured differently and can be
configured per port (ie. each port can have different ingress monitor
port, for example)
- port speed AltBit works differently than previously
- PHY registers can be also accessed via MDIO address 0x18 and 0x19
(on previous devices they could be accessed only via Global 2 offsets
0x18 and 0x19, which means two indirections; this feature is not yet
leveraged with thiis commit)

Co-developed-by: Ashkan Boldaji <ashkan.boldaji@digi.com>
Signed-off-by: Ashkan Boldaji <ashkan.boldaji@digi.com>
Signed-off-by: Pavana Sharma <pavana.sharma@digi.com>
Co-developed-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: change serdes lane parameter type from u8 type to int

Returning 0 is no more an error case with MV88E6393 family
which has serdes lane numbers 0, 9 or 10.
So with this change .serdes_get_lane will return lane number
or -errno (-ENODEV or -EOPNOTSUPP).

Signed-off-by: Pavana Sharma <pavana.sharma@digi.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Add serdes interrupt support for MV88E6097

The MV88E6097 presents the serdes interrupts for ports 8 and 9 via the
Switch Global 2 registers. There is no additional layer of
enablinh/disabling the serdes interrupts like other mv88e6xxx switches.
Even though most of the serdes behaviour is the same as the MV88E6185
that chip does not provide interrupts for serdes events so unlike
earlier commits the functions added here are specific to the MV88E6097.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net: dsa: mv88e6xxx: Support serdes ports on MV88E6097/6095/6185

Implement serdes_power, serdes_get_lane and serdes_pcs_get_state ops for
the MV88E6097/6095/6185 so that ports 8 & 9 can be supported as serdes
ports and directly connected to other network interfaces or to SFPs
without a PHY.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net: dsa: mv88e6xxx: 88e6390 10G serdes support

Add support for reading and reporting the 10G link status on the
88e6390 in addition to the 1000BASE-X/2500BASE-X/SGMII status.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: use generic clause 45 definitions

The private MV88E6390_PCS_CONTROL_1 definitions in serdes.h reflects
the IEEE 802.3 standard PCS control register 1 definitions, only
offset by 0x1000 in the PHYXS register space. Rather than inventing
our own, use those that already exist, and name the register
MV88E6390_10G_CTRL1.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: fix Serdes link changes

phylink_mac_change() is supposed to be called with a 'false' argument
if the link has gone down since it was last reported up; this is to
ensure that link events along with renegotiation events are always
correctly reported to userspace.

Read the BMSR once when we have an interrupt, and report the link
latched status to phylink via phylink_mac_change(). phylink will deal
automatically with re-reading the link state once it has processed the
link-down event.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: extend phylink to Serdes PHYs

Extend the mv88e6xxx phylink implementation down to Serdes PHYs, which
handle the PCS layer of such links.

- Implement phylink PCS link state reading, so that we can provide
ethtool with the linkmodes and link speed in the expected manner.
Note: this will only be called for in-band negotiation, which is
only supported by the serdes interfaces.
- Implement phylink PCS configuration, so that the in-band AN and
advertisement can be configured.
- Implement phylink PCS negotiation restart, so that the in-band AN
can be restarted.
- Implement phylink PCS link up, so that when operating out-of-band,
the Serdes can be configured for the appropriate fixed speed mode.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: use BMCR definitions for serdes control register

The SGMII/1000base-X serdes register set is a clause 22 register set
offset at 0x2000 in the PHYXS device. Rather than inventing our own
defintions, use those that already exist, and name the register
MV88E6390_SGMII_BMCR. Also remove the unused MV88E6390_SGMII_STATUS
definitions.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Add 6390 family PCS registers to ethtool -d

The mv88e6390 has upto 8 sets of PCS registers, depending on how ports
9 and 10 are configured. The can be spread over 8 ports. If a port has
a PCS register set, return it along with the port registers. The
register space is sparse, so hard code a list of registers which will
be returned. It can later be extended, if needed, by append to the end
of the list.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Add 6352 family PCS registers to ethtool -d

The mv88e6352 has one PCS which can be used for 1000BaseX or
SGMII. Add the registers to the dump for the port which the PCS is
associated to.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

mv88e6xxx: Add serdes Rx statistics

If packet checker is enabled in the serdes, then Rx counter registers
start working, and no side effects have been detected.

This patch enables packet checker automatically when powering serdes on,
and exposes Rx counter registers via ethtool statistics interface.

Code partially basded by older attempt by Andrew Lunn.

Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: centralize SERDES IRQ handling

The .serdes_irq_setup are all following the same steps: get the SERDES
lane, get the IRQ mapping, request the IRQ, then enable it. So do
the .serdes_irq_free implementations: get the SERDES lane, disable
the IRQ, then free it.

This patch removes these operations in favor of generic functions.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: introduce .serdes_irq_status

Introduce a new .serdes_irq_status operation to prepare the abstraction
of IRQ thread from the SERDES IRQ setup code.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: introduce .serdes_irq_enable

Introduce a new .serdes_irq_enable operation to prepare the abstraction
of IRQ enabling from the SERDES IRQ setup code.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: pass lane to .serdes_power

Now the first step of all .serdes_power implementations is getting
the lane mapping. Since we have an operation for that, call it in
the wrapper and pass the lane down to the .serdes_power operation.

This also allows to avoid querying the SERDES lane twice in
mv88e6xxx_port_set_cmode.

At the same time provide mv88e6xxx_serdes_power_{up,down} helpers
and prefer up/down instead of on/off as in the documentation.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: implement mv88e6352_serdes_get_lane

Even though 88E6352 has no dedicated lane for SERDES interfaces, it
uses a similar code as the other .serdes_get_lane implementations to
check the port's CMODE and ensure that SERDES operations are doable.

For consistency, implement mv88e6352_serdes_get_lane for the 88E6352
and similar switches which simply returns an unused 0xff lane address.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: simplify .serdes_get_lane

Because the mapping between a SERDES interface and its lane is static,
we don't need to stick with negative error codes actually and we can
simply return 0 if there is no lane, just like the IRQ mapping.

This way we can keep a simple and intuitive API using unsigned lane
numbers while simplifying the implementations with single return
statements. Last but not least, fix the reverse chrismas tree in
mv88e6390x_serdes_get_lane.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: introduce .serdes_irq_mapping

Introduce a new .serdes_irq_mapping operation to prepare the
abstraction of IRQ mapping from the SERDES IRQ setup code.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: simplify SERDES code for Topaz and Peridot

By adding an additional serdes_get_lane implementation (for Topaz), we
can merge the implementations of other SERDES functions (powering and
IRQs). We can skip checking port numbers, since the serdes_get_lane()
methods inform if there is no lane on a port or if the lane cannot be
used for given cmode.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: create serdes_get_lane chip operation

Create a serdes_get_lane() method in the mv88e6xxx operations structure.
Use it instead of calling the different implementations.
Also change the methods so that their return value is used only for
error. The lane number is put into a place referred to by a pointer
given as argument. If the port does not have a lane, return -ENODEV.
Lanes are phy addresses, so use u8 as their type.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Vivien Didelot <vivien.didelot@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 3029 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net: dsa: mv88e6xxx: support in-band signalling on SGMII ports with external PHYs

If an external PHY is connected via SGMII and uses in-band signalling
then the auto-negotiated values aren't propagated to the port,
resulting in a broken link. See discussion in [0]. This patch adds
this propagation. We need to call mv88e6xxx_port_setup_mac(),
therefore export it from chip.c.

Successfully tested on a ZII DTU with 88E6390 switch and an
Aquantia AQCS109 PHY connected via SGMII to port 9.

[0] https://marc.info/?t=155130287200001&r=1&w=2

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Add support for SERDES on ports 2-8 for 6390X

The 6390X family has 8 SERDES interfaces. When ports 9 and 10 are not
using all their SERDES interfaces, the unused ones can be assigned to
ports 2-8. Add support for interrupts from SERDES interfaces connected
to these lower ports.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Add SERDES phydev_link_change for 6352

The 6352 family has one SERDES interface, which can be used by either
port 4 or port 5. Add interrupt support for the SERDES interface, and
report when the link status changes.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Re-setup interrupts on CMODE change.

When a port changes CMODE, the SERDES interface being used can change.
Disable interrupts for the old SERDES interface, and enable interrupts
on the new.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Add SERDES phydev_mac_change up for 6390

phylink wants to know when the MAC layers notices a change in the
link. For the 6390 family, this is a change in the SERDES state.

Add interrupt support for the SERDES interface used to implement
SGMII/1000Base-X/2500Base-X. This is currently limited to ports 9 and
10. Support for the 10G SERDES and other ports will be added later,
building on this basic framework.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Add serdes register read/write helper

Add a helper for accessing SERDES registers of the 6390 family.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: 6390 vs 6390X SERDES support

The 6390 has two SERDES interfaces, used by ports 9 and 10. The 6390X
has eight SERDES interfaces. These allow ports 9 and 10 to do 10G. Or
if lower speeds are used, some of the SERDES interfaces can be used by
ports 2-8 for 1000Base-X.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: 88E6141/6341 SERDES support

The 88E6141/6341 switches (also known as Topaz) have 1 SGMII lane,
which can be configured the same way as the SERDES lane on 88E6390.

Signed-off-by: Marek Behun <marek.behun@nic.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Keep ATU/VTU violation statistics

Count the numbers of various ATU and VTU violation statistics and
return them as part of the ethtool -S statistics.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Get mv88e6352 SERDES statistics

Add support for reading the SERDES statistics of the mv88e8352, using
the standard ethtool -S option. The SERDES interface can be mapped to
either port 4 or 5, so only return statistics on those ports, if the
SERDES interface is in use.

The counters are reset on read, so need to be accumulated. Add a per
port structure to hold the stats counters. The 6352 only has a single
SERDES interface and so only one port will using the newly added
array. However the 6390 family has as many SERDES interfaces as ports,
each with statistics counters. Also, PTP has a number of counters per
port which will also need accumulating.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: rename chip header

The mv88e6xxx.h is meant to contains the chip structures and data.
Rename it to chip.h, as for other source/header pairs of the driver.

At the same time, ensure that relative header inclusions are separated
by a newline and sorted alphabetically.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: mv88e6390X SERDES support

The mv88e6390X family has 8 SERDES lanes. These can be used for 2
10Gbps ports, ports 9 or 10. If these ports are used at slower speeds,
the SERDES lanes become available for other ports for 1000Base-X.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: dsa: mv88e6xxx: Refactor mv88e6352 SERDES code into an op

The mv88e6390 family has a different SERDES implementation. Refactor
the mv88e6352 code into an ops function, so we can later add the
mv88e6390 code.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>