[PATCH net-next 2/3] ptp: netc: add the periodic output signal loopback support

[Vladimir Oltean]

On Wed, Sep 03, 2025 at 04:37:48PM +0800, Wei Fang wrote:
> 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 at nxp.com>
> ---

Reviewed-by: Vladimir Oltean <vladimir.oltean at nxp.com>