netdev - Re: [PATCH 1/2] net: dp83822: disable false carrier interrupt

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Date:   Thu, 23 Jun 2022 09:16:28 -0400 (EDT)
From:   Enguerrand de Ribaucourt 
        <enguerrand.de-ribaucourt@...oirfairelinux.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     davem <davem@...emloft.net>, netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux <linux@...linux.org.uk>, hkallweit1 <hkallweit1@...il.com>
Subject: Re: [PATCH 1/2] net: dp83822: disable false carrier interrupt

----- Original Message -----
> From: "Andrew Lunn" <andrew@...n.ch>
> To: "Enguerrand de Ribaucourt" <enguerrand.de-ribaucourt@...oirfairelinux.com>
> Cc: "davem" <davem@...emloft.net>, "netdev" <netdev@...r.kernel.org>, "linux-kernel" <linux-kernel@...r.kernel.org>,
> "linux" <linux@...linux.org.uk>, "hkallweit1" <hkallweit1@...il.com>
> Sent: Thursday, June 23, 2022 2:42:54 PM
> Subject: Re: [PATCH 1/2] net: dp83822: disable false carrier interrupt

> On Thu, Jun 23, 2022 at 10:51:25AM +0200, Enguerrand de Ribaucourt wrote:
> > 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.

> Since this is version 2, you should add v2 into the subject line. See
> the submitting patches document in the kernel documentation.

> Also, with patch sets, please include a patch 0/X which describes the
> big picture.

> This is also a bug fix, you are stopping an interrupt storm. So please
> include a Fixes: tag indicating where the issue was introduced.

> The code itself looks good, it is just getting the processes right.

> Andrew

Sorry, I'm still not familiar with the process. I resubmitted the patches
with your recommendations.

Thank you very much for your advice.
Enguerrand