[PATCH net-next v4 0/4] net: mdio: implement optional PHY reset before MDIO access

[Buday Csaba <buday.csaba@prolan.hu>]

Some Ethernet PHY devices require a hard reset before any MDIO access can
be safely performed. This includes the auto-detection of the PHY ID, which
is necessary to bind the correct driver to the device.

The kernel currently does not provide a way to assert the reset before
reading the ID, making these devices usable only when the ID is hardcoded
in the Device Tree 'compatible' string.
(One notable exception is the FEC driver and its now deprecated
`phy-reset-gpios` property).

This patchset implements an optional reset before reading of the PHY ID
register, allowing such PHYs to be used with auto-detected ID. The reset
is only asserted when the current logic fails to detect the ID, ensuring
compatibility with existing systems.

There have been several earlier attempts to implement such functionality,
of which I have collected a few in the links section.

The links to my own v1, v2 and v3 versions are also provided.
The most notable change compared to v3, is that the DT binding is removed,
and the hard-reset works as a fallback logic now.

Link: https://lore.kernel.org/lkml/1499346330-12166-2-git-send-email-richard.leitner@skidata.com/
Link: https://lore.kernel.org/all/20230405-net-next-topic-net-phy-reset-v1-0-7e5329f08002@pengutronix.de/
Link: https://lore.kernel.org/netdev/20250709133222.48802-4-buday.csaba@prolan.hu/
Link: https://lore.kernel.org/all/20251013135557.62949-1-buday.csaba@prolan.hu/
Link: https://lore.kernel.org/all/20251015134503.107925-1-buday.csaba@prolan.hu/
Link: https://lore.kernel.org/netdev/cover.1760620093.git.buday.csaba@prolan.hu/

Buday Csaba (4):
  net: mdio: common handling of phy reset properties
  net: mdio: change property read from fwnode_property_read_u32() to
    device_property_read_u32()
  net: mdio: introduce mdio_device_has_reset()
  net: mdio: reset PHY before attempting to access registers in
    fwnode_mdiobus_register_phy

 drivers/net/mdio/fwnode_mdio.c | 46 ++++++++++++++++++++----
 drivers/net/phy/mdio_bus.c     | 39 ++------------------
 drivers/net/phy/mdio_device.c  | 65 ++++++++++++++++++++++++++++++++++
 include/linux/mdio.h           |  3 ++
 4 files changed, 110 insertions(+), 43 deletions(-)


base-commit: 00922eeaca3c5c2001781bcad40e0bd54d0fdbb6
-- 
2.39.5