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Measurements of the MDIO bus have shown that driving the MDIO bus using interrupts is slow. Back to back MDIO transactions take about 90us, with 25us spent performing the transaction, and the remainder of the time the bus is idle. Replacing the completion interrupt with polled IO results in back to back transactions of 40us. The polling loop waiting for the hardware to complete the transaction takes around 28us. Which suggests interrupt handling has an overhead of 50us, and polled IO nearly halves this overhead, and doubles the MDIO performance. Suggested-by: Chris Heally <cphealy@gmail.com> Signed-off-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.