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Oleksij Rempel d0c3601f2c net: macb: Avoid 20s boot delay by skipping MDIO bus registration for fixed-link PHY 
A boot delay was introduced by commit 79540d133e ("net: macb: Fix
handling of fixed-link node"). This delay was caused by the call to
`mdiobus_register()` in cases where a fixed-link PHY was present. The
MDIO bus registration triggered unnecessary PHY address scans, leading
to a 20-second delay due to attempts to detect Clause 45 (C45)
compatible PHYs, despite no MDIO bus being attached.

The commit 79540d133e ("net: macb: Fix handling of fixed-link node")
was originally introduced to fix a regression caused by commit
7897b071ac ("net: macb: convert to phylink"), which caused the driver
to misinterpret fixed-link nodes as PHY nodes. This resulted in warnings
like:
mdio_bus f0028000.ethernet-ffffffff: fixed-link has invalid PHY address
mdio_bus f0028000.ethernet-ffffffff: scan phy fixed-link at address 0
...
mdio_bus f0028000.ethernet-ffffffff: scan phy fixed-link at address 31

This patch reworks the logic to avoid registering and allocation of the
MDIO bus when:
  - The device tree contains a fixed-link node.
  - There is no "mdio" child node in the device tree.

If a child node named "mdio" exists, the MDIO bus will be registered to
support PHYs  attached to the MACB's MDIO bus. Otherwise, with only a
fixed-link, the MDIO bus is skipped.

Tested on a sama5d35 based system with a ksz8863 switch attached to
macb0.

Fixes: 79540d133e ("net: macb: Fix handling of fixed-link node")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: stable@vger.kernel.org
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20241013052916.3115142-1-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
History 2024-10-15 10:40:47 -07:00
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README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.