ptp: netc: add the periodic output signal loopback support

The NETC Timer supports looping back the output pulse signal of Fiper-n
into Trigger-n input, so that users can leverage this feature to validate
some other features without external hardware support. For example, users
can use it to test external trigger stamp (EXTTS). And users can combine
EXTTS with loopback mode to check whether the generation time of PPS is
aligned with an integral second of PHC, or the periodic output signal
(PTP_CLK_REQ_PEROUT) whether is generated at the specified time.

Since ptp_clock_info::perout_loopback() has been added to the ptp_clock
driver as a generic interface to enable or disable the periodic output
signal loopback, therefore, netc_timer_perout_loopback() is added as a
callback of ptp_clock_info::perout_loopback().

Test the generation time of PPS event:

$ echo 0 1 > /sys/kernel/debug/ptp0/perout_loopback
$ echo 1 > /sys/class/ptp/ptp0/pps_enable
$ testptp -d /dev/ptp0 -e 3
external time stamp request okay
event index 0 at 63.000000017
event index 0 at 64.000000017
event index 0 at 65.000000017

Test the generation time of the periodic output signal:

$ echo 0 1 > /sys/kernel/debug/ptp0/perout_loopback
$ echo 0 150 0 1 500000000 > /sys/class/ptp/ptp0/period
$ testptp -d /dev/ptp0 -e 3
external time stamp request okay
event index 0 at 150.000000014
event index 0 at 151.500000015
event index 0 at 153.000000014

Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20250905030711.1509648-3-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions