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The NETC Timer is capable of generating a PPS interrupt to the host. To support this feature, a 64-bit alarm time (which is a integral second of PHC in the future) is set to TMR_ALARM, and the period is set to TMR_FIPER. The alarm time is compared to the current time on each update, then the alarm trigger is used as an indication to the TMR_FIPER starts down counting. After the period has passed, the PPS event is generated. According to the NETC block guide, the Timer has three FIPERs, any of which can be used to generate the PPS events, but in the current implementation, we only need one of them to implement the PPS feature, so FIPER 0 is used as the default PPS generator. Also, the Timer has 2 ALARMs, currently, ALARM 0 is used as the default time comparator. However, if the time is adjusted or the integer of period is changed when PPS is enabled, the PPS event will not be generated at an integral second of PHC. The suggested steps from IP team if time drift happens: 1. Disable FIPER before adjusting the hardware time 2. Rearm ALARM after the time adjustment to make the next PPS event be generated at an integral second of PHC. 3. Re-enable FIPER. Signed-off-by: Wei Fang <wei.fang@nxp.com> Reviewed-by: Frank Li <Frank.Li@nxp.com> Link: https://patch.msgid.link/20250829050615.1247468-6-wei.fang@nxp.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> |
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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 reStructuredText 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.