linux-kernel - [PATCH 5.8 40/99] igc: Fix wrong timestamp latency numbers

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Message-Id: <20200929105931.696666656@linuxfoundation.org>
Date:   Tue, 29 Sep 2020 13:01:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Aaron Brown <aaron.f.brown@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.8 40/99] igc: Fix wrong timestamp latency numbers

From: Vinicius Costa Gomes <vinicius.gomes@...el.com>

[ Upstream commit f03369b9bfab8e23ac28ca7ab7e6631c374b7cbe ]

The previous timestamping latency numbers were obtained by
interpolating the i210 numbers with the i225 crystal clock value. That
calculation was wrong.

Use the correct values from real measurements.

Fixes: 81b055205e8b ("igc: Add support for RX timestamping")
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
Tested-by: Aaron Brown <aaron.f.brown@...el.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/intel/igc/igc.h | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
index 5dbc5a156626a..206b73aa6d7a7 100644
--- a/drivers/net/ethernet/intel/igc/igc.h
+++ b/drivers/net/ethernet/intel/igc/igc.h
@@ -298,18 +298,14 @@ extern char igc_driver_version[];
 #define IGC_RX_HDR_LEN			IGC_RXBUFFER_256
 
 /* Transmit and receive latency (for PTP timestamps) */
-/* FIXME: These values were estimated using the ones that i225 has as
- * basis, they seem to provide good numbers with ptp4l/phc2sys, but we
- * need to confirm them.
- */
-#define IGC_I225_TX_LATENCY_10		9542
-#define IGC_I225_TX_LATENCY_100		1024
-#define IGC_I225_TX_LATENCY_1000	178
-#define IGC_I225_TX_LATENCY_2500	64
-#define IGC_I225_RX_LATENCY_10		20662
-#define IGC_I225_RX_LATENCY_100		2213
-#define IGC_I225_RX_LATENCY_1000	448
-#define IGC_I225_RX_LATENCY_2500	160
+#define IGC_I225_TX_LATENCY_10		240
+#define IGC_I225_TX_LATENCY_100		58
+#define IGC_I225_TX_LATENCY_1000	80
+#define IGC_I225_TX_LATENCY_2500	1325
+#define IGC_I225_RX_LATENCY_10		6450
+#define IGC_I225_RX_LATENCY_100		185
+#define IGC_I225_RX_LATENCY_1000	300
+#define IGC_I225_RX_LATENCY_2500	1485
 
 /* RX and TX descriptor control thresholds.
  * PTHRESH - MAC will consider prefetch if it has fewer than this number of
-- 
2.25.1