netdev - Re: No traffic with Marvell switch and latest linux-next

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Date:   Sun, 24 Feb 2019 16:28:32 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: No traffic with Marvell switch and latest linux-next

On 24.02.2019 16:15, Russell King - ARM Linux admin wrote:
> On Sun, Feb 24, 2019 at 04:04:03PM +0100, Andrew Lunn wrote:
>>> I think what's not correct is that phydev->autoneg is set
>>> (by phy_device_create) for a fixed link.
>>
>> Fixed-link tries to emulate auto-neg:
>>
>>                 bmsr |= BMSR_LSTATUS | BMSR_ANEGCOMPLETE;
>>
>> Maybe it needs better emulation of auto-neg?
> 
> Or maybe it needs to represent a fixed-speed PHY by clearing bit 1.3
> (BMSR_ANEGCAPABLE).  In any case, 0.12 (BMCR_ANENABLE) is not set,
> so according to 802.3-2015, we should not be setting 1.5
> (BMSR_ANEGCOMPLETE).
> 
> However, swphy does try to emulate autonegotiation - we do have cases
> where swphy is used in situations where the speed and duplex are not
> fixed.  It returns an emulated link partner advertisement for the
> current speed, which would suggest that we should set BMCR_ANENABLE.
> 
If we emulate auto-neg, then it's not needed to set the speed bits
in BMCR. Also what just comes to my mind, certain speeds like 1000BaseT
don't support forced mode. So we may have to go with auto-neg.
To avoid the original issue it should be sufficient to copy
supported -> advertising at a suited place.