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Subject: Re: [PATCH 2/2] dt-bindings: net: dsa: qca8k: Add PORT0_PAD_CTRL
 properties
To:     Matthew Hagan <mnhagan88@gmail.com>,
        Jakub Kicinski <kuba@kernel.org>, Andrew Lunn <andrew@lunn.ch>
Cc:     Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        "David S. Miller" <davem@davemloft.net>, linux@armlinux.org.uk,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jonathan McDowell <noodles@earth.li>,
        Rob Herring <robh+dt@kernel.org>, devicetree@vger.kernel.org
References: <2e1776f997441792a44cd35a16f1e69f848816ce.1594668793.git.mnhagan88@gmail.com>
 <ea0a35ed686e6dace77e25cb70a8f39fdd1ea8ad.1594668793.git.mnhagan88@gmail.com>
 <20200716150925.0f3e01b8@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
 <ac7f5f39-9f83-64c0-d8d5-9ea059619f67@gmail.com>
From:   John Crispin <john@phrozen.org>
Message-ID: <53851852-0efe-722e-0254-8652cdfea8fc@phrozen.org>
Date:   Fri, 17 Jul 2020 22:44:19 +0200
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On 17.07.20 22:29, Matthew Hagan wrote:
>
> On 16/07/2020 23:09, Jakub Kicinski wrote:
>> On Mon, 13 Jul 2020 21:50:26 +0100 Matthew Hagan wrote:
>>> Add names and decriptions of additional PORT0_PAD_CTRL properties.
>>>
>>> Signed-off-by: Matthew Hagan <mnhagan88@gmail.com>
>>> ---
>>>   Documentation/devicetree/bindings/net/dsa/qca8k.txt | 8 ++++++++
>>>   1 file changed, 8 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/net/dsa/qca8k.txt b/Documentation/devicetree/bindings/net/dsa/qca8k.txt
>>> index ccbc6d89325d..3d34c4f2e891 100644
>>> --- a/Documentation/devicetree/bindings/net/dsa/qca8k.txt
>>> +++ b/Documentation/devicetree/bindings/net/dsa/qca8k.txt
>>> @@ -13,6 +13,14 @@ Optional properties:
>>>   
>>>   - reset-gpios: GPIO to be used to reset the whole device
>>>   
>>> +Optional MAC configuration properties:
>>> +
>>> +- qca,exchange-mac0-mac6:	If present, internally swaps MAC0 and MAC6.
>> Perhaps we can say a little more here?
>>
>  From John's patch:
> "The switch allows us to swap the internal wirering of the two cpu ports.
> For the HW offloading to work the ethernet MAC conencting to the LAN
> ports must be wired to cpu port 0. There is HW in the wild that does not
> fulfill this requirement. On these boards we need to swap the cpu ports."
>
> This option is somewhat linked to instances where both MAC0 and MAC6 are
> used as CPU ports. I may omit this for now since support for this hasn't
> been added and MAC0 is hard-coded as the CPU port. The initial intention
> here was to cover options commonly set by OpenWrt devices, based upon
> their ar8327-initvals, to allow migration to qca8k.
>
>
correct, specifically quantenna designs do this, also saw ciscos swap 
mac0/6 for cpu port, that part of the patch is definitely safe to go. I 
stumbled across this while making qca8k work for g-fiber on a quantenna SoC.

in regards to the sgmii clk skew. I never understood the electrics fully 
I am afraid, but without the patch it simply does not work. my eletcric 
foo is unfortunately is not sufficient to understand the "whys" I am afraid.

     John