netdev - Re: [PATCH 2/2] dt-bindings: net: dsa: qca8k: Add PORT0_PAD

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Date:   Fri, 17 Jul 2020 22:44:19 +0200
From:   John Crispin <john@...ozen.org>
To:     Matthew Hagan <mnhagan88@...il.com>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>
Cc:     Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>, linux@...linux.org.uk,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jonathan McDowell <noodles@...th.li>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH 2/2] dt-bindings: net: dsa: qca8k: Add PORT0_PAD_CTRL
 properties


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@...il.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