netdev - Re: [PATCH v2 04/14] dt-bindings: arm: mediatek: document WED binding for MT7622

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Message-ID: <750c1f9e-6a53-16d5-390e-f9f81fa23afd@linaro.org>
Date:   Wed, 6 Apr 2022 10:57:21 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Felix Fietkau <nbd@....name>, Arnd Bergmann <arnd@...db.de>
Cc:     Networking <netdev@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        DTML <devicetree@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC..." 
        <linux-mediatek@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 04/14] dt-bindings: arm: mediatek: document WED binding
 for MT7622

On 06/04/2022 10:32, Felix Fietkau wrote:
> On 06.04.22 10:29, Arnd Bergmann wrote:
>> On Wed, Apr 6, 2022 at 10:18 AM Felix Fietkau <nbd@....name>
>> wrote:
>>> On 06.04.22 10:09, Krzysztof Kozlowski wrote:
>>>> On 05/04/2022 21:57, Felix Fietkau wrote:
>>>>> From: Lorenzo Bianconi <lorenzo@...nel.org>
>>>>> 
>>>>> Document the binding for the Wireless Ethernet Dispatch core
>>>>> on the MT7622 SoC, which is used for Ethernet->WLAN
>>>>> offloading Add related info in mediatek-net bindings.
>>>>> 
>>>>> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org> 
>>>>> Signed-off-by: Felix Fietkau <nbd@....name>
>>>> 
>>>> Thank you for your patch. There is something to
>>>> discuss/improve.
>>>> 
>>>>> --- .../arm/mediatek/mediatek,mt7622-wed.yaml     | 50
>>>>> +++++++++++++++++++ 
>>>>> .../devicetree/bindings/net/mediatek-net.txt  |  2 + 2 files
>>>>> changed, 52 insertions(+) create mode 100644
>>>>> Documentation/devicetree/bindings/arm/mediatek/mediatek,mt7622-wed.yaml
>>>>
>>>>
>>>>> 
Don't store drivers in arm directory. See:
>>>> https://lore.kernel.org/linux-devicetree/YkJa1oLSEP8R4U6y@robh.at.kernel.org/
>>>>
>>>>
>>>> 
Isn't this a network offload engine? If yes, then probably it should be
>>>> in "net/".
>>> It's not a network offload engine by itself. It's a SoC component
>>> that connects to the offload engine and controls a MTK PCIe WLAN
>>> device, intercepting interrupts and DMA rings in order to be able
>>> to inject packets coming in from the offload engine. Do you think
>>> it still belongs in net, or maybe in soc instead?
>> 
>> I think it belongs into drivers/net/. Presumably this has some kind
>> of user interface to configure which packets are forwarded? I would
>> not want to maintain that in a SoC driver as this clearly needs to
>> communicate with both of the normal network devices in some form.
> The WLAN driver attaches to WED in order to deal with the intercepted
>  DMA rings, but other than that, WED itself has no user
> configuration. Offload is controlled by the PPE code in the ethernet
> driver (which is already upstream), and WED simply provides a
> destination port for PPE, which allows packets to flow to the
> wireless device.

Thanks for clarification. I still wonder about the missing drivers as I
responded to your second bindings:
https://lore.kernel.org/all/20220405195755.10817-1-nbd@nbd.name/T/#m6d108c644f0c05cd12c05e56abe2ef75760c6cef

Both of these compatibles - WED and PCIe - are not actually used. Now
everything is done inside your Ethernet driver which pokes WED and
PCIe-mirror address space via regmap/syscon.

Separate bindings might have sense if WED/PCIe mirror were ever
converted to real drivers.

Best regards,
Krzysztof