[Intel-wired-lan] [PATCH 2/2] igc: Fix not considering the TX delay for timestamps

Vinicius Costa Gomes vinicius.gomes at intel.com
Mon Aug 17 23:12:31 UTC 2020


When timestamping a packet there's a delay between the start of the
packet and the point where the hardware actually captures the
timestamp. This difference needs to be considered if we want accurate
timestamps.

This was done on the RX side, but not on the TX side.

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes at intel.com>
---
 drivers/net/ethernet/intel/igc/igc_ptp.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/net/ethernet/intel/igc/igc_ptp.c b/drivers/net/ethernet/intel/igc/igc_ptp.c
index f78e9acb801f..a841ac1088aa 100644
--- a/drivers/net/ethernet/intel/igc/igc_ptp.c
+++ b/drivers/net/ethernet/intel/igc/igc_ptp.c
@@ -366,6 +366,7 @@ static void igc_ptp_tx_hwtstamp(struct igc_adapter *adapter)
 	struct sk_buff *skb = adapter->ptp_tx_skb;
 	struct skb_shared_hwtstamps shhwtstamps;
 	struct igc_hw *hw = &adapter->hw;
+	int adjust = 0;
 	u64 regval;
 
 	if (WARN_ON_ONCE(!skb))
@@ -375,6 +376,24 @@ static void igc_ptp_tx_hwtstamp(struct igc_adapter *adapter)
 	regval |= (u64)rd32(IGC_TXSTMPH) << 32;
 	igc_ptp_systim_to_hwtstamp(adapter, &shhwtstamps, regval);
 
+	switch (adapter->link_speed) {
+	case SPEED_10:
+		adjust = IGC_I225_TX_LATENCY_10;
+		break;
+	case SPEED_100:
+		adjust = IGC_I225_TX_LATENCY_100;
+		break;
+	case SPEED_1000:
+		adjust = IGC_I225_TX_LATENCY_1000;
+		break;
+	case SPEED_2500:
+		adjust = IGC_I225_TX_LATENCY_2500;
+		break;
+	}
+
+	shhwtstamps.hwtstamp =
+		ktime_add_ns(shhwtstamps.hwtstamp, adjust);
+
 	/* Clear the lock early before calling skb_tstamp_tx so that
 	 * applications are not woken up before the lock bit is clear. We use
 	 * a copy of the skb pointer to ensure other threads can't change it
-- 
2.28.0



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