Markus Niebel e1b505a603 net: phy: micrel: add 125MHz reference clock workaround
The micrel KSZ9031 phy has a optional clock pin (CLK125_NDO) which can be
used as reference clock for the MAC unit. The clock signal must meet the
RGMII requirements to ensure the correct data transmission between the
MAC and the PHY. The KSZ9031 phy does not fulfill the duty cycle
requirement if the phy is configured as slave. For a complete
describtion look at the errata sheets: DS80000691D or DS80000692D.

The errata sheet recommends to force the phy into master mode whenever
there is a 1000Base-T link-up as work around. Only set the
"micrel,force-master" property if you use the phy reference clock provided
by CLK125_NDO pin as MAC reference clock in your application.

Attenation, this workaround is only usable if the link partner can
be configured to slave mode for 1000Base-T.

Signed-off-by: Markus Niebel <Markus.Niebel@tqs.de>
[m.felsch@pengutronix.de: fix dt-binding documentation]
[m.felsch@pengutronix.de: use already existing result var for read/write]
[m.felsch@pengutronix.de: add error handling]
[m.felsch@pengutronix.de: add more comments]
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-05-16 12:20:03 -04:00

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

There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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    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.
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