From: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Date: Tue, 18 Aug 2020 16:40:02 -0700
Subject: igc: Fix not considering the TX delay for timestamps
Patch-mainline: v5.9-rc7
Git-commit: 4406e977a4a1e997818b6d77c3218ef8d15b2abf
References: jsc#SLE-13533

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.

Fixes: 2c344ae24501 ("igc: Add support for TX timestamping")
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/intel/igc/igc_ptp.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

--- a/drivers/net/ethernet/intel/igc/igc_ptp.c
+++ b/drivers/net/ethernet/intel/igc/igc_ptp.c
@@ -364,6 +364,7 @@ static void igc_ptp_tx_hwtstamp(struct i
 	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))
@@ -373,6 +374,24 @@ static void igc_ptp_tx_hwtstamp(struct i
 	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