igc: Fix PPS delta between two synchronized end-points

igc: Fix PPS delta between two synchronized end-points

[ Upstream commit 5e91c72e560cc85f7163bbe3d14197268de31383 ]

This patch fix the pulse per second output delta between
two synchronized end-points.

Based on Intel Discrete I225 Software User Manual Section
4.2.15 TimeSync Auxiliary Control Register, ST0[Bit 4] and
ST1[Bit 7] must be set to ensure that clock output will be
toggles based on frequency value defined. This is to ensure
that output of the PPS is aligned with the clock.

How to test:

1) Running time synchronization on both end points.
Ex: ptp4l --step_threshold=1 -m -f gPTP.cfg -i <interface name>

2) Configure PPS output using below command for both end-points
Ex: SDP0 on I225 REV4 SKU variant

./testptp -d /dev/ptp0 -L 0,2
./testptp -d /dev/ptp0 -p 1000000000

3) Measure the output using analyzer for both end-points

Fixes: 0d7904b52b4d ("igc: enable auxiliary PHC functions for the i225")
Signed-off-by: Christopher S Hall <christopher.s.hall@intel.com>
Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@intel.com>
Acked-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>