netdev - Re: genphy_read_status() vs. 1000bT Pause capability

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Message-ID: <20170328113104.GY7909@n2100.armlinux.org.uk>
Date:   Tue, 28 Mar 2017 12:31:05 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org
Subject: Re: genphy_read_status() vs. 1000bT Pause capability

On Tue, Mar 28, 2017 at 10:11:24PM +1100, Benjamin Herrenschmidt wrote:
> On Tue, 2017-03-28 at 10:42 +0100, Russell King - ARM Linux wrote:
> > The 1000X definitions are for 1000BaseX (fiber), not for 1000BaseT
> > (copper).
> > 
> > I have a working setup here with gigabit pause.  The pause bits come
> > from bits 11 and 10, just like for older copper PHYs.  Your link
> > parter is indicating that it has no pause capability.  That means
> > you can't use pause.
> 
> Interesting. I tried and it worked :-) Could be something funny in
> the config of our switches.

It could be that the switch supports pause frames, but it's not
advertised because there's some corner cases that it doesn't work.  I
know that SolidRun have run into switches that corrupt ethernet frames
when pause is used.  (I don't know off hand which they are, but I could
ask the question.)

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.