netdev - [PATCH] net: dp83822: disable false carrier interrupt

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Date:   Fri, 17 Jun 2022 15:46:11 +0200
From:   Enguerrand de Ribaucourt 
        <enguerrand.de-ribaucourt@...oirfairelinux.com>
To:     andrew@...n.ch, davem@...emloft.net
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux@...linux.org.uk, hkallweit1@...il.com,
        Enguerrand de Ribaucourt 
        <enguerrand.de-ribaucourt@...oirfairelinux.com>
Subject: [PATCH] net: dp83822: disable false carrier interrupt

When unplugging an Ethernet cable, false carrier events were produced by
the PHY at a very high rate. Once the false carrier counter full, an
interrupt was triggered every few clock cycles until the cable was
replugged. This resulted in approximately 10k/s interrupts.

Since the false carrier counter (FCSCR) is never used, we can safely
disable this interrupt.

In addition to improving performance, this also solved MDIO read
timeouts I was randomly encountering with an i.MX8 fec MAC because of
the interrupt flood. The interrupt count and MDIO timeout fix were
tested on a v5.4.110 kernel.

Signed-off-by: Enguerrand de Ribaucourt <enguerrand.de-ribaucourt@...oirfairelinux.com>
---
 drivers/net/phy/dp83822.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/phy/dp83822.c b/drivers/net/phy/dp83822.c
index e6ad3a494d32..95ef507053a6 100644
--- a/drivers/net/phy/dp83822.c
+++ b/drivers/net/phy/dp83822.c
@@ -230,7 +230,6 @@ static int dp83822_config_intr(struct phy_device *phydev)
 			return misr_status;

 		misr_status |= (DP83822_RX_ERR_HF_INT_EN |
-				DP83822_FALSE_CARRIER_HF_INT_EN |
 				DP83822_LINK_STAT_INT_EN |
 				DP83822_ENERGY_DET_INT_EN |
 				DP83822_LINK_QUAL_INT_EN);
-- 
2.25.1