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

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Date:   Tue, 28 Mar 2017 10:42:52 +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 04:17:18PM +1100, Benjamin Herrenschmidt wrote:
> I added a printk inside genphy_read_status() to inspect the result
> of the negociation, and this is what I read:
> 
> lpa=c1e1 lpagb=3800 adv=de1 common_adv=1e1 common_adv_gb=800
> 
> As you can see, LPA doesn't have the Pause bits. *However* it does
> have bit 0x80 which can mean ADVERTISE_100HALF, but according to
> our own mii.h can also mean ADVERTISE_1000XPAUSE. Similarily it 
> has bit 0x100 which can mean ADVERTISE_100FULL but also can mean
> ADVERTISE_1000XPSE_ASYM.

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.

-- 
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.