netdev - Re: [net: PATCH] net: mvpp2: disable link IRQ waiting for IDLE frames

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Message-Id: <20190423.102608.343500084156113302.davem@davemloft.net>
Date:   Tue, 23 Apr 2019 10:26:08 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     mw@...ihalf.com
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        netdev@...r.kernel.org, antoine.tenart@...tlin.com,
        jaz@...ihalf.com, gregory.clement@...tlin.com, nadavh@...vell.com,
        thomas.petazzoni@...tlin.com, linux@...linux.org.uk,
        tn@...ihalf.com, stefanc@...vell.com
Subject: Re: [net: PATCH] net: mvpp2: disable link IRQ waiting for IDLE
 frames

From: Marcin Wojtas <mw@...ihalf.com>
Date: Tue, 23 Apr 2019 18:08:00 +0200

> Hi David, Rusell,
> 
> czw., 28 lut 2019 o 14:58 Marcin Wojtas <mw@...ihalf.com> napisa┅(a):
>>
>> Hi Russell,
>>
>> czw., 28 lut 2019 o 10:36 Russell King - ARM Linux admin
>> <linux@...linux.org.uk> napisa┅(a):
>> >
>> > On Wed, Feb 27, 2019 at 06:47:32PM +0100, Marcin Wojtas wrote:
>> > > Current version of the driver was configuring XLG MAC
>> > > in a way to wait 3 IDLE frames before allowing for the
>> > > link-up interrupt to be triggered. This resulted in an
>> > > issue, preventing to detect the link change during RX
>> > > traffic on the interface. Fix that.
>> >
>> > What about noise sensitivity?  Does this now mean that on boards such as
>> > Macchiatobin Single Shot or Clearfog GT9k where the serdes is connected
>> > directly to a SFP cage, that noise on the serdes lines triggers a link
>> > indication?
>> >
>>
>> Afaik waiting for idle frames is not required by any standard. In fact
>> this feature of the XLG MAC caused a risk that after dropping the link
>> during data transfer it would never go up again until remote peer
>> stops it.
>>
>> I tested it on 3 different boards with SerDes directly connected to
>> the SFP cage and I'm also not aware of any reporte about
>> noise-triggered false link interrupts in XLG MAC (proprietary Marvell
>> mvpp2x driver did not use waiting 3 idle frames feature). I'd rather
>> assume the MAC is not vulnerable to it, and only properly established
>> link can trigger an event.
>>
> 
> This patch seems to get forgotten - any objections to merge it?

If there is agreement, please repost it.

Thank you.