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On some machines (nami), interrupt latency cause samples to appear
to be from the future and are pegged to the current time.
We would see samples with this pattern:
[t, t + ~5ms, t + ~10ms, t + ~10ms + 100us, t + ~10ms + 200us],
(current now) (current now)
(t is the last timestamp time)
Last 2 samples would be barely spread, causing applications to
complain.
We now spread the entire sequence. This is not great: in the example
the sensor was supposed to send samples every 5ms, it now appears to
send one every 2.5ms, but it is slightly closer to reality:
sampling time in the example above
At sensor level
1 2 3 4 5
+-----5ms-----+-----5ms-----+-----5ms-----+----5ms-----+---> t
Before, at host level
1 2 3 4 5
--interrupt delay------+-----5ms-----+-----5ms-----+-+-+---> t
Afer, at host level
1 2 3 4 5
--interrupt delay------+-2.5ms-+-2.5ms-+-2.5ms-+-2.5ms-+---> t
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.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.