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0ba83aa037
It looks like the sja1105 external timestamping input is not as generic
as we thought. When fed a signal with 50% duty cycle, it will timestamp
both the rising and the falling edge. When fed a short pulse signal,
only the timestamp of the falling edge will be seen in the PTPSYNCTS
register, because that of the rising edge had been overwritten. So the
moral is: don't feed it short pulse inputs.
Luckily this is not a complete deal breaker, as we can still work with
1 Hz square waves. But the problem is that the extts polling period was
not dimensioned enough for this input signal. If we leave the period at
half a second, we risk losing timestamps due to jitter in the measuring
process. So we need to increase it to 4 times per second.
Also, the very least we can do to inform the user is to deny any other
flags combination than with PTP_RISING_EDGE and PTP_FALLING_EDGE both
set.
Fixes:
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.