linux-kernel - [PATCH net 1/2] net: stmmac: fix dwmac1000 ptp timestamp status offset

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Message-Id: <20250422-stmmac_ts-v1-1-b59c9f406041@bootlin.com>
Date: Tue, 22 Apr 2025 17:07:22 +0200
From: Alexis Lothore <alexis.lothore@...tlin.com>
To: Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Maxime Coquelin <mcoquelin.stm32@...il.com>, 
 Alexandre Torgue <alexandre.torgue@...s.st.com>, 
 Richard Cochran <richardcochran@...il.com>, 
 Daniel Machon <daniel.machon@...rochip.com>, 
 Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>, netdev@...r.kernel.org, 
 linux-stm32@...md-mailman.stormreply.com, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 "Russell King (Oracle)" <linux@...linux.org.uk>, 
 Alexis Lothoré <alexis.lothore@...tlin.com>
Subject: [PATCH net 1/2] net: stmmac: fix dwmac1000 ptp timestamp status
 offset

When a PTP interrupt occurs, the driver accesses the wrong offset to
learn about the number of available snapshots in the FIFO for dwmac1000:
it should be accessing bits 29..25, while it is currently reading bits
19..16 (those are bits about the auxiliary triggers which have generated
the timestamps). As a consequence, it does not compute correctly the
number of available snapshots, and so possibly do not generate the
corresponding clock events if the bogus value ends up being 0.

Fix clock events generation by reading the correct bits in the timestamp
register for dwmac1000.

Fixes: 19b93bbb20eb ("net: stmmac: Introduce dwmac1000 timestamping operations")
Signed-off-by: Alexis Lothoré <alexis.lothore@...tlin.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac1000.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac1000.h b/drivers/net/ethernet/stmicro/stmmac/dwmac1000.h
index 967a16212faf008bc7b5e43031e2d85800c5c467..0c011a47d5a3e98280a98d25b8ef3614684ae78c 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac1000.h
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac1000.h
@@ -320,8 +320,8 @@ enum rtc_control {

 /* PTP and timestamping registers */

-#define GMAC3_X_ATSNS       GENMASK(19, 16)
-#define GMAC3_X_ATSNS_SHIFT 16
+#define GMAC3_X_ATSNS       GENMASK(29, 25)
+#define GMAC3_X_ATSNS_SHIFT 25

 #define GMAC_PTP_TCR_ATSFC	BIT(24)
 #define GMAC_PTP_TCR_ATSEN0	BIT(25)

-- 
2.49.0