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[ Upstream commited8fe20205] When debugging another issue I faced an interrupt storm in this driver (88E6390, port 9 in SGMII mode), consisting of alternating link-up / link-down interrupts. Analysis showed that the driver wanted to set a cmode that was set already. But so far mv88e6390x_port_set_cmode() doesn't check this and powers down SERDES, what causes the link to break, and eventually results in the described interrupt storm. Fix this by checking whether the cmode actually changes. We want that the very first call to mv88e6390x_port_set_cmode() always configures the registers, therefore initialize port.cmode with a value that is different from any supported cmode value. We have to take care that we only init the ports cmode once chip->info->num_ports is set. v2: - add small helper and init the number of actual ports only Fixes:364e9d7776("net: dsa: mv88e6xxx: Power on/off SERDES on cmode change") Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.