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The power up defaults of the MPLL are designed for the standard 125MHz refclock derived from the ENET PLL. As this clock has a jitter that violates the PCIe Gen2 timing requirements, some board designs use an external reference clock generator. Those clock generators may output a clock at a different rate than what the MPLL expects (usually a 100MHz clock, to re-use the PCIe bus clock). In that case the MPLL must be reconfigured via overrides to use different refclock dividers and loop multipliers. The i.MX6 reference manual lists both 100MHz and 200MHz as supported refclock rates and the associated mult and div values. Only the 100MHz setup has been tested on a real board, but since the 200MHz setup only differs in the used pre-divider it seems safe to add it now. Signed-off-by: Lucas Stach <l.stach@pengutronix.de> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Reviewed-by: Richard Zhu <hongxing.zhu@nxp.com>
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.