ice: track and warn when PHC update is late

The ice driver requires a cached copy of the PHC time in order to perform
timestamp extension on Tx and Rx hardware timestamp values. This cached PHC
time must always be updated at least once every 2 seconds. Otherwise, the
math used to perform the extension would produce invalid results.

The updates are supposed to occur periodically in the PTP kthread work
item, which is scheduled to run every half second. Thus, we do not expect
an update to be delayed for so long. However, there are error conditions
which can cause the update to be delayed.

Track this situation by using jiffies to determine approximately how long
ago the last update occurred. Add a new statistic and a dev_warn when we
have failed to update the cached PHC time. This makes the error case more
obvious.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Gurucharan <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

1 files changed, 25 insertions, 3 deletions

diff --git a/drivers/net/ethernet/intel/ice/ice_ptp.c b/drivers/net/ethernet/intel/ice/ice_ptp.c
index c1758f7bd091..10352eca2ecd 100644
--- a/drivers/net/ethernet/intel/ice/ice_ptp.c
+++ b/drivers/net/ethernet/intel/ice/ice_ptp.c
@@ -507,17 +507,30 @@ ice_ptp_read_src_clk_reg(struct ice_pf *pf, struct ptp_system_timestamp *sts)
  */
 static int ice_ptp_update_cached_phctime(struct ice_pf *pf)
 {
+	struct device *dev = ice_pf_to_dev(pf);
+	unsigned long update_before;
 	u64 systime;
 	int i;
 
 	if (test_and_set_bit(ICE_CFG_BUSY, pf->state))
 		return -EAGAIN;
 
+	update_before = pf->ptp.cached_phc_jiffies + msecs_to_jiffies(2000);
+	if (pf->ptp.cached_phc_time &&
+	    time_is_before_jiffies(update_before)) {
+		unsigned long time_taken = jiffies - pf->ptp.cached_phc_jiffies;
+
+		dev_warn(dev, "%u msecs passed between update to cached PHC time\n",
+			 jiffies_to_msecs(time_taken));
+		pf->ptp.late_cached_phc_updates++;
+	}
+
 	/* Read the current PHC time */
 	systime = ice_ptp_read_src_clk_reg(pf, NULL);
 
 	/* Update the cached PHC time stored in the PF structure */
 	WRITE_ONCE(pf->ptp.cached_phc_time, systime);
+	WRITE_ONCE(pf->ptp.cached_phc_jiffies, jiffies);
 
 	ice_for_each_vsi(pf, i) {
 		struct ice_vsi *vsi = pf->vsi[i];
@@ -636,6 +649,14 @@ static u64 ice_ptp_extend_32b_ts(u64 cached_phc_time, u32 in_tstamp)
 static u64 ice_ptp_extend_40b_ts(struct ice_pf *pf, u64 in_tstamp)
 {
 	const u64 mask = GENMASK_ULL(31, 0);
+	unsigned long discard_time;
+
+	/* Discard the hardware timestamp if the cached PHC time is too old */
+	discard_time = pf->ptp.cached_phc_jiffies + msecs_to_jiffies(2000);
+	if (time_is_before_jiffies(discard_time)) {
+		pf->ptp.tx_hwtstamp_discarded++;
+		return 0;
+	}
 
 	return ice_ptp_extend_32b_ts(pf->ptp.cached_phc_time,
 				     (in_tstamp >> 8) & mask);
@@ -2104,9 +2125,10 @@ static void ice_ptp_tx_tstamp_work(struct kthread_work *work)
 
 		/* Extend the timestamp using cached PHC time */
 		tstamp = ice_ptp_extend_40b_ts(pf, raw_tstamp);
-		shhwtstamps.hwtstamp = ns_to_ktime(tstamp);
-
-		ice_trace(tx_tstamp_complete, skb, idx);
+		if (tstamp) {
+			shhwtstamps.hwtstamp = ns_to_ktime(tstamp);
+			ice_trace(tx_tstamp_complete, skb, idx);
+		}
 
 		skb_tstamp_tx(skb, &shhwtstamps);
 		dev_kfree_skb_any(skb);