e3f0cc1a94
A number of users have reported that they were not able to get the PHY
to successfully link up, especially after commit c36757eb9dee ("net:
phy: consider AN_RESTART status when reading link status") where we
stopped reading just BMSR, but we also read BMCR to determine the link
status.
Andrius at NetBSD did a wonderful job at debugging the problem
and found out that the MDIO bus clock frequency would be incorrectly set
back to its default value which would prevent the MDIO bus controller
from reading PHY registers properly. Back when we only read BMSR, if we
read all 1s, we could falsely indicate a link status, though in general
there is a cable plugged in, so this went unnoticed. After a second read
of BMCR was added, a wrong read will lead to the inability to determine
a link UP condition which is when it started to be visibly broken, even
if it was long before that.
The fix consists in restoring the value of the MD_CSR register that was
set prior to the MAC reset.
Link: http://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=53494
Fixes: 90f750a81a29 ("r6040: consolidate MAC reset to its own function")
Reported-by: Andrius V <vezhlys@gmail.com>
Reported-by: Darek Strugacz <darek.strugacz@op.pl>
Tested-by: Darek Strugacz <darek.strugacz@op.pl>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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 Restructured Text 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.