linux-kernel - [PATCH] net: sparx5: Fix invalid timestamps

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Message-ID: <20240913193357.21899-1-aakash.menon@protempis.com>
Date: Fri, 13 Sep 2024 12:33:57 -0700
From: Aakash Menon <aakash.r.menon@...il.com>
To: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	lars.povlsen@...rochip.com,
	Steen.Hegelund@...rochip.com,
	daniel.machon@...rochip.com,
	UNGLinuxDriver@...rochip.com,
	aakash.menon@...tempis.com,
	horms@...nel.org,
	horatiu.vultur@...rochip.com
Cc: netdev@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] net: sparx5: Fix invalid timestamps

Bit 270-271 are occasionally unexpectedly set by the hardware.

This issue was observed with 10G SFPs causing huge time errors (> 30ms) in PTP.

Only 30 bits are needed for the nanosecond part of the timestamp, clear 2 most significant bits before extracting timestamp from the internal frame header.

Signed-off-by: Aakash Menon <aakash.menon@...tempis.com>
---
 drivers/net/ethernet/microchip/sparx5/sparx5_packet.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
index f3f5fb420468..a05263488851 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
@@ -45,8 +45,12 @@ void sparx5_ifh_parse(u32 *ifh, struct frame_info *info)
 	fwd = (fwd >> 5);
 	info->src_port = FIELD_GET(GENMASK(7, 1), fwd);
 
+	/*
+	 * Bit 270-271 are occasionally unexpectedly set by the hardware,
+	 * clear bits before extracting timestamp
+	 */
 	info->timestamp =
-		((u64)xtr_hdr[2] << 24) |
+		((u64)(xtr_hdr[2] & 0x3F) << 24) |
 		((u64)xtr_hdr[3] << 16) |
 		((u64)xtr_hdr[4] <<  8) |
 		((u64)xtr_hdr[5] <<  0);
-- 
2.46.0