[PATCH iwl-net] ice: restore PTP Rx timestamp config after ethtool set-channels

[Grzegorz Nitka <grzegorz.nitka@intel.com>]

When ethtool -L changes queue counts, ice_vsi_recfg_qs() closes and
rebuilds the VSI, reallocating Rx rings. The newly allocated rings have
ptp_rx cleared, so RX hardware timestamps are no longer attached to skb
until hwtstamp configuration is applied again.

Restore timestamp mode after ice_vsi_open() in the queue reconfiguration
path, matching reset/rebuild behavior and ensuring newly rebuilt Rx rings
have PTP RX timestamping re-enabled.

Testing hints:
- run ptp4l application in client synchronization mode:
	 ptp4l -i ethX -m -s
- run PTP traffic
- change queue number on ethX netdev interface:
	ethtool -L ethX combined new_queue_size
- observe ptp4l output
- expected result: no "received DELAY_REQ without timestamp" messages

Fixes: 77a781155a65 ("ice: enable receive hardware timestamping")
Cc: stable@vger.kernel.org
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Grzegorz Nitka <grzegorz.nitka@intel.com>
---
 drivers/net/ethernet/intel/ice/ice_main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
index 79f2906eda99..b87accaf7d14 100644
--- a/drivers/net/ethernet/intel/ice/ice_main.c
+++ b/drivers/net/ethernet/intel/ice/ice_main.c
@@ -4110,6 +4110,12 @@ int ice_vsi_recfg_qs(struct ice_vsi *vsi, int new_rx, int new_tx, bool locked)
 	}
 	ice_pf_dcb_recfg(pf, locked);
 	ice_vsi_open(vsi);
+	/* Rx rings are reallocated during VSI rebuild and lose their ptp_rx
+	 * flag. Restore timestamp mode so newly allocated rings are set up
+	 * for hardware Rx timestamping.
+	 */
+	if (test_bit(ICE_FLAG_PTP_SUPPORTED, pf->flags))
+		ice_ptp_restore_timestamp_mode(pf);
 	goto done;
 
 rebuild_err:

base-commit: f0cfdedb42fe64b06fd048bd490ef835beeda658
-- 
2.39.3