netdev - [PATCH] Use ixgbe_ptp_reset on linkup/linkdown for X550

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Date:   Mon,  1 Aug 2022 06:37:50 -0700
From:   achaiken@...ora.tech
To:     jesse.brandeburg@...el.com, richardcochran@...il.com
Cc:     spayne@...ora.tech, achaiken@...ora.tech, alison@...-devel.com,
        netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org
Subject: [PATCH] Use ixgbe_ptp_reset on linkup/linkdown for X550

From: Steve Payne <spayne@...ora.tech>

For an unknown reason, when `ixgbe_ptp_start_cyclecounter` is called
from `ixgbe_watchdog_link_is_down` the PHC on the NIC jumps backward
by a seemingly inconsistent amount, which causes discontinuities in
time synchronization. Explicitly reset the NIC's PHC to
`CLOCK_REALTIME` whenever the NIC goes up or down by calling
`ixgbe_ptp_reset` instead of the bare `ixgbe_ptp_start_cyclecounter`.

Signed-off-by: Steve Payne <spayne@...ora.tech>
Signed-off-by: Alison Chaiken <achaiken@...ora.tech>

---
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 750b02bb2fdc2..ab1ec076fa75f 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -7462,7 +7462,7 @@ static void ixgbe_watchdog_link_is_up(struct ixgbe_adapter *adapter)
 	adapter->last_rx_ptp_check = jiffies;
 
 	if (test_bit(__IXGBE_PTP_RUNNING, &adapter->state))
-		ixgbe_ptp_start_cyclecounter(adapter);
+		ixgbe_ptp_reset(adapter);
 
 	switch (link_speed) {
 	case IXGBE_LINK_SPEED_10GB_FULL:
@@ -7527,7 +7527,7 @@ static void ixgbe_watchdog_link_is_down(struct ixgbe_adapter *adapter)
 		adapter->flags2 |= IXGBE_FLAG2_SEARCH_FOR_SFP;
 
 	if (test_bit(__IXGBE_PTP_RUNNING, &adapter->state))
-		ixgbe_ptp_start_cyclecounter(adapter);
+		ixgbe_ptp_reset(adapter);
 
 	e_info(drv, "NIC Link is Down\n");
 	netif_carrier_off(netdev);
-- 
2.32.0