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

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Message-ID: <YAtcVw4hctU1Bv6E@lunn.ch>
Date:   Sat, 23 Jan 2021 00:14:31 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     netdev@...r.kernel.org, Heiner Kallweit <hkallweit1@...il.com>,
        kernel@...gutronix.de, Dan Murphy <dmurphy@...com>
Subject: Re: [PATCH] net: dp83tc811: fix link detection and possbile IRQ storm

On Fri, Jan 22, 2021 at 04:03:34PM +0100, Marc Kleine-Budde wrote:
> 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>

Hi Marc

Seems reasonable. Please add to your rebased version:

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew