mirror of https://gitee.com/openkylin/linux.git
bb77f36ac2
The design of this PHC driver is influenced by the switch's behavior w.r.t. timestamping. It exposes two PTP counters, one free-running (PTPTSCLK) and the other offset- and frequency-corrected in hardware through PTPCLKVAL, PTPCLKADD and PTPCLKRATE. The MACs can sample either of these for frame timestamps. However, the user manual warns that taking timestamps based on the corrected clock is less than useful, as the switch can deliver corrupted timestamps in a variety of circumstances. Therefore, this PHC uses the free-running PTPTSCLK together with a timecounter/cyclecounter structure that translates it into a software time domain. Thus, the settime/adjtime and adjfine callbacks are hardware no-ops. The timestamps (introduced in a further patch) will also be translated to the correct time domain before being handed over to the userspace PTP stack. The introduction of a second set of PHC operations that operate on the hardware PTPCLKVAL/PTPCLKADD/PTPCLKRATE in the future is somewhat unavoidable, as the TTEthernet core uses the corrected PTP time domain. However, the free-running counter + timecounter structure combination will suffice for now, as the resulting timestamps yield a sub-50 ns synchronization offset in steady state using linuxptp. For this patch, in absence of frame timestamping, the operations of the switch PHC were tested by syncing it to the system time as a local slave clock with: phc2sys -s CLOCK_REALTIME -c swp2 -O 0 -m -S 0.01 Signed-off-by: Vladimir Oltean <olteanv@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| arch | ||
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| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
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| Kbuild | ||
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| Makefile | ||
| README | ||
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.