c11669a275
The code was assuming the reset default of the delay control register was to have delay disabled. This is what the datasheet shows as the register's initial value. However, that's not actually true: the default is controlled by the PHY's pin strapping. If the interface mode is selected as RX or TX delay only, insure the other direction's delay is disabled. If the interface mode is just "rgmii", with neither TX or RX internal delay, one might expect that the driver should disable both delays. But this is not what the driver does. It leaves the setting at the PHY's strapping's default. And that default, for no pins with strapping resistors, is to have delay enabled and 2.00 ns. Rather than change this behavior, I've kept it the same and documented it. No delay will most likely not work and will break ethernet on any board using "rgmii" mode. If the board is strapped to have a delay and is configured to use "rgmii" mode a warning is generated that "rgmii-id" should have been used. Also validate the delay values and fail if they are not in range. Cc: Andrew Lunn <andrew@lunn.ch> Cc: Florian Fainelli <f.fainelli@gmail.com> Cc: Heiner Kallweit <hkallweit1@gmail.com> Signed-off-by: Trent Piepho <tpiepho@impinj.com> Reviewed-by: Andrew Lunn <andrew@lunn.ch> 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.