netdev - [PATCH] net: dp83tc811: fix link detection and possbile IRQ storm

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Message-Id: <20210122150334.2378703-1-mkl@pengutronix.de>
Date:   Fri, 22 Jan 2021 16:03:34 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     netdev@...r.kernel.org
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>, kernel@...gutronix.de,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Dan Murphy <dmurphy@...com>
Subject: [PATCH] net: dp83tc811: fix link detection and possbile IRQ storm

In our setup the dp83tc811 is configure to master mode. When there is no slave
connected the dp83tc811 triggers an interrupt is triggerd, several bits in the
status registers are set, and te INT_N pin goes low. One of interrupt bits is
the NO_FRAME interrupt.

Reading the status register acknowledges the interrupt, but as there is still
no slave connected, the NO_FRAME interrupt stays set and the INT_N pin low. For
level triggered IRQs this results in an interrupt storm, as long as the slave
is not connected. For edge triggered interupts the link change event, when the
slave comes online, is lost.

To fix this problem the NO_FRAME interrupt is not enabled. At least in our
testcase with edge triggered interrupts link change events are now properly
detected.

Cc: Dan Murphy <dmurphy@...com>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 drivers/net/phy/dp83tc811.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/phy/dp83tc811.c b/drivers/net/phy/dp83tc811.c
index b8d802cbf615..2801492bfaad 100644
--- a/drivers/net/phy/dp83tc811.c
+++ b/drivers/net/phy/dp83tc811.c
@@ -222,7 +222,6 @@ static int dp83811_config_intr(struct phy_device *phydev)
 			return err;

 		misr_status = (DP83811_LPS_INT_EN |
-			       DP83811_NO_FRAME_INT_EN |
 			       DP83811_POR_DONE_INT_EN);

 		err = phy_write(phydev, MII_DP83811_INT_STAT3, misr_status);
-- 
2.29.2