From: David Laight <David.Laight@ACULAB.COM>
To: 'Timur Tabi' <timur@codeaurora.org>,
"David S. Miller" <davem@davemloft.net>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: RE: [PATCH 1/2] [for 4.13] net: qcom/emac: disable flow control autonegotiation by default
Date: Wed, 2 Aug 2017 13:48:18 +0000 [thread overview]
Message-ID: <063D6719AE5E284EB5DD2968C1650D6DD00490C0@AcuExch.aculab.com> (raw)
In-Reply-To: <1501623460-3575-2-git-send-email-timur@codeaurora.org>
From: Timur Tabi
> Sent: 01 August 2017 22:38
> The EMAC has a curious qwirk when RX flow control is enabled and the
> kernel hangs. With the kernel hung, the EMAC's RX queue soon fills.
> If RX flow control is enabled, the EMAC will then send a non-stop
> stream of pause frames until the system is reset. The EMAC does not
> have a built-in watchdog.
>
> In various tests, the pause frame stream sometimes overloads nearby
> switches, effectively disabling the network.
...
If the nearby switches cannot handle pause frames, then the MAC shouldn't
be sending them at all.
They
I suspect that they should only ever be sent if the phy autonegotiation
indicates that they are supported.
You might want to avoid sending them even if allowed, or advertise
non-support on hardware that could support them, but sending them
anyway is likely to cause grief.
This is similar to the problems that arise when the 'speed' is forced
instead of limiting the advertised speed to one value.
David
next prev parent reply other threads:[~2017-08-02 13:48 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-01 21:37 [PATCH 0/2] net: qcom/emac: fixes for pause frame floods Timur Tabi
2017-08-01 21:37 ` [PATCH 1/2] [for 4.13] net: qcom/emac: disable flow control autonegotiation by default Timur Tabi
2017-08-01 21:55 ` Florian Fainelli
2017-08-01 22:02 ` Timur Tabi
2017-08-01 22:08 ` Florian Fainelli
2017-08-01 23:15 ` Andrew Lunn
2017-08-02 0:56 ` Timur Tabi
2017-08-02 2:58 ` Andrew Lunn
2017-08-02 3:22 ` Timur Tabi
2017-08-02 13:48 ` David Laight [this message]
2017-08-02 14:21 ` Timur Tabi
2017-08-02 14:51 ` David Laight
2017-08-02 15:08 ` Timur Tabi
2017-08-02 15:38 ` David Laight
2017-08-02 17:54 ` David Miller
2017-08-02 18:23 ` Timur Tabi
2017-08-02 18:35 ` David Miller
2017-08-02 18:39 ` Timur Tabi
2017-08-02 23:15 ` David Miller
2017-08-03 1:00 ` Timur Tabi
2017-08-02 18:36 ` David Miller
2017-08-01 21:37 ` [PATCH 2/2] net: qcom/emac: add software control for pause frame mode Timur Tabi
2017-08-01 21:51 ` Florian Fainelli
2017-08-01 22:00 ` Timur Tabi
2017-08-01 22:06 ` Florian Fainelli
2017-09-12 22:07 ` Timur Tabi
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