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1060707e38
Many drivers implement the .adjfreq or .adjfine PTP op function with the
same basic logic:
1. Determine a base frequency value
2. Multiply this by the abs() of the requested adjustment, then divide by
the appropriate divisor (1 billion, or 65,536 billion).
3. Add or subtract this difference from the base frequency to calculate a
new adjustment.
A few drivers need the difference and direction rather than the combined
new increment value.
I recently converted the Intel drivers to .adjfine and the scaled parts per
million (65.536 parts per billion) logic. To avoid overflow with minimal
loss of precision, mul_u64_u64_div_u64 was used.
The basic logic used by all of these drivers is very similar, and leads to
a lot of duplicate code to perform the same task.
Rather than keep this duplicate code, introduce diff_by_scaled_ppm and
adjust_by_scaled_ppm. These helper functions calculate the difference or
adjustment necessary based on the scaled parts per million input.
The diff_by_scaled_ppm function returns true if the difference should be
subtracted, and false otherwise.
Update the Intel drivers to use the new helper functions. Other vendor
drivers will be converted to .adjfine and this helper function in the
following changes.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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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.