linux-kernel - [PATCH net] amd-xgbe: read link status twice to avoid inconsistencies

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Message-ID: <20250514194145.3681817-1-Raju.Rangoju@amd.com>
Date: Thu, 15 May 2025 01:11:45 +0530
From: Raju Rangoju <Raju.Rangoju@....com>
To: <andrew+netdev@...n.ch>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>
CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<Shyam-sundar.S-k@....com>, Raju Rangoju <Raju.Rangoju@....com>
Subject: [PATCH net] amd-xgbe: read link status twice to avoid inconsistencies

The link status is latched low, so read the register twice to get the
current status and avoid link inconsistencies.

As per IEEE 802.3 "Table 22-8 - Status register bit definitions"
1.2  Link Status  1 = link is up    0 = link is down    RO/LL

Fixes: 4f3b20bfbb75 ("amd-xgbe: add support for rx-adaptation")
Signed-off-by: Raju Rangoju <Raju.Rangoju@....com>
---
 drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c b/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
index 268399dfcf22..d233e3faa1a9 100644
--- a/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
+++ b/drivers/net/ethernet/amd/xgbe/xgbe-phy-v2.c
@@ -2914,6 +2914,10 @@ static int xgbe_phy_link_status(struct xgbe_prv_data *pdata, int *an_restart)
 		}
 
 		/* check again for the link and adaptation status */
+		/* Link status is latched low, so read once to clear
+		 * and then read again to get current state
+		 */
+		reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
 		reg = XMDIO_READ(pdata, MDIO_MMD_PCS, MDIO_STAT1);
 		if ((reg & MDIO_STAT1_LSTATUS) && pdata->rx_adapt_done)
 			return 1;
-- 
2.34.1