Merge branch 'net-mtk_eth_soc-improve-pcs-implementation'

Russell King says:

====================
net: mtk_eth_soc: improve PCS implementation

As a result of invesigations from Frank Wunderlich, we know a lot more
about the Mediatek "SGMII" PCS block, and can implement the PCS support
correctly. This series achieves that, and Frank has tested the final
result and reports that it works for him. The series could do with
further testing by others, but I suspect that is unlikely to happen
until it is merged based on past performances with this driver.

Briefly, the patches in order:

1. Add a new helper to get the link timer duration in nanoseconds
2. Add definitions for the newly discovered registers and updates to
   bit definitions, including bitmasks for the BMCR, BMSR and two
   advertisement registers.
3. Remove unnecessary/unused error handling (functions always returning
   zero.)
4. Adding the missing pcs_get_state() implementation.
5. Converting the code to use regmap_update_bits() rather than
   open-coding read-modify-write sequences.
6. Adding out-of-band speed and duplex forcing for all non-inband modes
   not just the 802.3z link modes the code currently does.
7. Moving the release of the PHY power down to the main pcs_config()
   function.
8. Moving the interface speed selection to the main pcs_config()
   function.
9. Adding advertisement programming.
10. Adding correct link timer programming using the new helper in the
    first patch.
11. Adding support for 802.3z negotiation.

There is one remaining issue - when configuring the PCS for in-band,
for some reason the AN restart bit is always set. This should not be
necessary, but requires further investigation with the hardware to
find out whether it is really necessary. I suspect this was a work
around for a previous poor implementation.
====================

Link: https://lore.kernel.org/r/Y1qDMw+DJLAJHT40@shell.armlinux.org.uk


Signed-off-by: Jakub Kicinski <kuba@kernel.org>