[PATCH net-next v5 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 the previous versions are also provided.
The most notable changes compared to v4 are:
 - -EPROBE_DEFER during the reset is propagated upward, while any other
   errors retain the original error code
 - The info level message for asserting the reset is split into a
   separate commit.

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/
Link: https://lore.kernel.org/netdev/cover.1761124022.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: reset PHY before attempting to access registers in
    fwnode_mdiobus_register_phy
  net: mdio: add message when resetting a PHY before registration

 drivers/net/mdio/fwnode_mdio.c | 48 +++++++++++++++++++++----
 drivers/net/phy/mdio_bus.c     | 39 ++------------------
 drivers/net/phy/mdio_device.c  | 66 ++++++++++++++++++++++++++++++++++
 include/linux/mdio.h           |  3 ++
 4 files changed, 113 insertions(+), 43 deletions(-)


base-commit: 00922eeaca3c5c2001781bcad40e0bd54d0fdbb6
-- 
2.39.5