net: usb: lan78xx: Refactor USB link power configuration into helper

Move the USB link power configuration logic from lan78xx_link_reset()
to a new helper function lan78xx_configure_usb(). This simplifies the
main link reset path and isolates USB-specific logic.

The new function handles U1/U2 enablement based on Ethernet link speed,
but only for SuperSpeed-capable devices (LAN7800 and LAN7801). LAN7850,
a High-Speed-only device, is explicitly excluded. A warning is logged
if SuperSpeed is reported unexpectedly for LAN7850.

Add a forward declaration for lan78xx_configure_usb() as preparation for
the upcoming phylink conversion, where it will also be used from the
mac_link_up() callback.

Open questions remain:

- Why is the 1000 Mbps configuration split into two steps (U2 disable,
  then U1 enable), unlike the single-step config used for 10/100 Mbps?

- U1/U2 behavior appears to depend on proper EEPROM configuration.
  There are known devices in the field without EEPROM. Should the driver
  enforce safe defaults in such cases?

Due to lack of USB subsystem expertise, no changes were made to this logic
beyond structural refactoring.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

0 files changed, 0 insertions, 0 deletions