netdev - Re: Toggling link state breaks network connectivity

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Message-ID: <6edad982-713a-1b38-d9f0-e763c70c4f95@gmail.com>
Date:   Tue, 13 Jun 2017 08:50:17 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Mason <slash.tmp@...e.fr>, netdev <netdev@...r.kernel.org>
Cc:     Andrew Lunn <andrew@...n.ch>, Mans Rullgard <mans@...sr.com>,
        Thibaud Cornic <thibaud_cornic@...madesigns.com>
Subject: Re: Toggling link state breaks network connectivity



On 06/13/2017 08:47 AM, Mason wrote:
> On 13/06/2017 17:36, Florian Fainelli wrote:
> 
>> On 06/13/2017 08:07 AM, Mason wrote:
>>
>>> I did note something that seems important.
>>> If I toggle the link state in software, then connectivity breaks.
>>> If I unplug the ethernet cable, and replug, connectivity remains.
>>
>> What does that actually mean? If you disconnect the cable a link state
>> should be notified and another link state should be notified, even if
>> that happens faster than the PHYLIB polling time (1s).
> 
> Sorry for being unclear.
> 
> If I unplug/replug the cable, ping still works afterward.
> (Packet RX appears to be *not* wedged)
> 
> If I toggle the link state in SW (set link down/set link up),
> I can no longer ping afterward.
> (Packet RX appears to be wedged, so ARP replies are not seen)
> 
> Maybe the two experiments are too unrelated to consider
> the different results relevant in any way?

No, they are not, this really tells you that whatever your ndo_open()
and ndo_stop() functions do, they are currently broken with your
particular HW. I have seen numerous problems on some of our older
platforms using bcmgenet where the PHY needs to be reset *before* any
MAC activity occurs, and any MAC activity even qualifies as a reset of
the MAC itself, we can perform a PHY reset there because the PHY is
internal, that may not be an option, and your HW is different anyway.
-- 
Florian