A-Team_Digital_Solutions/android_kernel_motorola_sm6375
Watch
2
0
Fork
You've already forked android_kernel_motorola_sm6375
 0
mirror of https://github.com/BobTheBlinker/android_kernel_motorola_sm6375.git synced 2026-10-28 10:41:38 -04:00
Code Issues Projects Releases Packages Wiki Activity

ptp: Add PTP_SYS_OFFSET_PRECISE for driver crosstimestamping

Browse source 
Currently, network /system cross-timestamping is performed in the
PTP_SYS_OFFSET ioctl. The PTP clock driver reads gettimeofday() and
the gettime64() callback provided by the driver. The cross-timestamp
is best effort where the latency between the capture of system time
(getnstimeofday()) and the device time (driver callback) may be
significant.

The getcrosststamp() callback and corresponding PTP_SYS_OFFSET_PRECISE
ioctl allows the driver to perform this device/system correlation when
for example cross timestamp hardware is available. Modern Intel
systems can do this for onboard Ethernet controllers using the ART
counter. There is virtually zero latency between captures of the ART
and network device clock.

The capabilities ioctl (PTP_CLOCK_GETCAPS), is augmented allowing
applications to query whether or not drivers implement the
getcrosststamp callback, providing more precise cross timestamping.

Cc: Prarit Bhargava <[email protected]>
Cc: Richard Cochran <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Acked-by: Richard Cochran <[email protected]>
Signed-off-by: Christopher S. Hall <[email protected]>
[jstultz: Commit subject tweaks]
Signed-off-by: John Stultz <[email protected]>
This commit is contained in:
Christopher S. Hall 2016-02-22 03:15:25 -08:00 • committed by John Stultz
commit 719f1aa4a6
4 changed files with 51 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

6
Documentation/ptp/testptp.c
View file

@ -277,13 +277,15 @@ int main(int argc, char *argv[])
" %d external time stamp channels\n"
" %d programmable periodic signals\n"
" %d pulse per second\n"
" %d programmable pins\n",
" %d programmable pins\n"
" %d cross timestamping\n",
caps.max_adj,
caps.n_alarm,
caps.n_ext_ts,
caps.n_per_out,
caps.pps,
caps.n_pins);
caps.n_pins,
caps.cross_timestamping);
}
}