netdev - Re: b53 tags on bpi-r1 (bcm53125)

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Date:   Thu, 23 Nov 2017 09:18:32 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Jochen Friedrich <jochen@...am.de>
Cc:     netdev@...r.kernel.org
Subject: Re: b53 tags on bpi-r1 (bcm53125)

Hi Jochen,

On 11/23/2017 09:05 AM, Jochen Friedrich wrote:
> Hi Florian,
> 
> 
>> OK, because this is a 53125S, it should support Broadcom tags correctly,
>> not clear yet what is happening. Just to make sure, you are using
>> arch/arm/boot/dts/sun7i-a20-lamobo-r1.dts as the DTS for this platform,
>> right?
> 
> Yes, that's the DTS I'm using.
> 
>> If so, can you provide the ethtool -k eth0 output and/or see if
>> disabling HW VLAN tag support for eth0 helps in any way?
> 
> It looks like gmac doesn't have HW VLAN support.

OK, good. I was wondering if this could confuse the GMAC HW into
thinking Broadcom tags where VLAN tags.

With Broadcom tags (or any type of switch tagging protocol), eth0
becomes a conduit interface and no longer a "normal" network device for
applications/socket to use. This means that if you were obtaining an IP
address through a DHCP client using e.g: dhclient eth0, this now needs
to be replaced using dhclient lan1 for instance.

If you use the per-port network devices, do you actually see Broadcom
tags coming out of these interfaces, or is it just when you use eth0
like what you used before that you see that happening?

If this is the former, then we are still back to square one, as this
really should not happen, if this is the latter, it means we need to
update any network scripts to properly make use of DSA-enabled network
devices and use only the per-port network devices now.

Thanks!
-- 
Florian