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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Enguerrand de Ribaucourt 
        <enguerrand.de-ribaucourt@savoirfairelinux.com>,
        Andrew Lunn <andrew@lunn.ch>, Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 4.19 07/79] net: dp83822: disable false carrier interrupt
Date:   Tue, 13 Sep 2022 16:06:25 +0200
Message-Id: <20220913140349.214011981@linuxfoundation.org>
In-Reply-To: <20220913140348.835121645@linuxfoundation.org>
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From: Enguerrand de Ribaucourt <enguerrand.de-ribaucourt@savoirfairelinux.com>

commit c96614eeab663646f57f67aa591e015abd8bd0ba upstream.

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.

Fixes: 87461f7a58ab ("net: phy: DP83822 initial driver submission")
Signed-off-by: Enguerrand de Ribaucourt <enguerrand.de-ribaucourt@savoirfairelinux.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/phy/dp83822.c |    1 -
 1 file changed, 1 deletion(-)

--- a/drivers/net/phy/dp83822.c
+++ b/drivers/net/phy/dp83822.c
@@ -204,7 +204,6 @@ static int dp83822_config_intr(struct ph
 			return misr_status;
 
 		misr_status |= (DP83822_RX_ERR_HF_INT_EN |
-				DP83822_FALSE_CARRIER_HF_INT_EN |
 				DP83822_ANEG_COMPLETE_INT_EN |
 				DP83822_DUP_MODE_CHANGE_INT_EN |
 				DP83822_SPEED_CHANGED_INT_EN |