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Yangbo Lu says:
====================
ptp: support virtual clocks and timestamping
Current PTP driver exposes one PTP device to user which binds network
interface/interfaces to provide timestamping. Actually we have a way
utilizing timecounter/cyclecounter to virtualize any number of PTP
clocks based on a same free running physical clock for using.
The purpose of having multiple PTP virtual clocks is for user space
to directly/easily use them for multiple domains synchronization.
user
space: ^ ^
| SO_TIMESTAMPING new flag: | Packets with
| SOF_TIMESTAMPING_BIND_PHC | TX/RX HW timestamps
v v
+--------------------------------------------+
sock: | sock (new member sk_bind_phc) |
+--------------------------------------------+
^ ^
| ethtool_get_phc_vclocks | Convert HW timestamps
| | to sk_bind_phc
v v
+--------------+--------------+--------------+
vclock: | ptp1 | ptp2 | ptpN |
+--------------+--------------+--------------+
pclock: | ptp0 free running |
+--------------------------------------------+
The block diagram may explain how it works. Besides the PTP virtual
clocks, the packet HW timestamp converting to the bound PHC is also
done in sock driver. For user space, PTP virtual clocks can be
created via sysfs, and extended SO_TIMESTAMPING API (new flag
SOF_TIMESTAMPING_BIND_PHC) can be used to bind one PTP virtual clock
for timestamping.
The test tool timestamping.c (together with linuxptp phc_ctl tool) can
be used to verify:
# echo 4 > /sys/class/ptp/ptp0/n_vclocks
[ 129.399472] ptp ptp0: new virtual clock ptp2
[ 129.404234] ptp ptp0: new virtual clock ptp3
[ 129.409532] ptp ptp0: new virtual clock ptp4
[ 129.413942] ptp ptp0: new virtual clock ptp5
[ 129.418257] ptp ptp0: guarantee physical clock free running
#
# phc_ctl /dev/ptp2 set 10000
# phc_ctl /dev/ptp3 set 20000
#
# timestamping eno0 2 SOF_TIMESTAMPING_TX_HARDWARE SOF_TIMESTAMPING_RAW_HARDWARE SOF_TIMESTAMPING_BIND_PHC
# timestamping eno0 2 SOF_TIMESTAMPING_RX_HARDWARE SOF_TIMESTAMPING_RAW_HARDWARE SOF_TIMESTAMPING_BIND_PHC
# timestamping eno0 3 SOF_TIMESTAMPING_TX_HARDWARE SOF_TIMESTAMPING_RAW_HARDWARE SOF_TIMESTAMPING_BIND_PHC
# timestamping eno0 3 SOF_TIMESTAMPING_RX_HARDWARE SOF_TIMESTAMPING_RAW_HARDWARE SOF_TIMESTAMPING_BIND_PHC
Changes for v2:
- Converted to num_vclocks for creating virtual clocks.
- Guranteed physical clock free running when using virtual
clocks.
- Fixed build warning.
- Updated copyright.
Changes for v3:
- Supported PTP virtual clock in default in PTP driver.
- Protected concurrency of ptp->num_vclocks accessing.
- Supported PHC vclocks query via ethtool.
- Extended SO_TIMESTAMPING API for PHC binding.
- Converted HW timestamps to PHC bound, instead of previous
binding domain value to PHC idea.
- Other minor fixes.
Changes for v4:
- Used do_aux_work callback for vclock refreshing instead.
- Used unsigned int for vclocks number, and max_vclocks
for limitiation.
- Fixed mutex locking.
- Dynamically allocated memory for vclock index storage.
- Removed ethtool ioctl command for vclocks getting.
- Updated doc for ethtool phc vclocks get.
- Converted to mptcp_setsockopt_sol_socket_timestamping().
- Passed so_timestamping for sock_set_timestamping.
- Fixed checkpatch/build.
- Other minor fixed.
Changes for v5:
- Fixed checkpatch/build/bug reported by test robot.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
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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 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.