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When using PPS mode, the input clock needs to be scaled so that we have
an IMU sample rate between (optimally) 4000 and 4250. After this, we can
use the decimation filter to lower the sampling rate in order to get what
the user wants. Optimally, the user sample rate is a multiple of both the
IMU sample rate and the input clock. Hence, calculating the sync_scale
dynamically gives us better chances of achieving a perfect/integer value
for DEC_RATE. The math here is:
1. lcm of the input clock and the desired output rate.
2. get the highest multiple of the previous result lower than the adis
max rate.
3. The last result becomes the IMU sample rate. Use that to calculate
SYNC_SCALE and DEC_RATE (to get the user output rate).
Fixes: 326e235755 ("iio: imu: adis16480: Add support for external clock")
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20210218114039.216091-2-nuno.sa@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.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.
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.