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The AR8031/AR8033 and the AR8035 support cable diagnostics. Adding driver support is straightforward, so lets add it. The PHY just do one pair at a time, so we have to start the test four times. The cable_test_get_status() can block and therefore we can just busy poll the test completion and continue with the next pair until we are done. The time delta counter seems to run at 125MHz which just gives us a resolution of about 82.4cm per tick. 100m cable, A/B/C/D open: Cable test started for device eth0. Cable test completed for device eth0. Pair: Pair A, result: Open Circuit Pair: Pair A, fault length: 107.94m Pair: Pair B, result: Open Circuit Pair: Pair B, fault length: 104.64m Pair: Pair C, result: Open Circuit Pair: Pair C, fault length: 105.47m Pair: Pair D, result: Open Circuit Pair: Pair D, fault length: 107.94m 1m cable, A/B connected, C shorted, D open: Cable test started for device eth0. Cable test completed for device eth0. Pair: Pair A, result: OK Pair: Pair B, result: OK Pair: Pair C, result: Short within Pair Pair: Pair C, fault length: 0.82m Pair: Pair D, result: Open Circuit Pair: Pair D, fault length: 0.82m Signed-off-by: Michael Walle <michael@walle.cc> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Reviewed-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.