A20-SOM204 - Enabling 2x ethernet

[winci45]

Dear all,
I am using last stable olimage (A20-OLinuXino-buster-minimal-20200601-122725) on the A20-SOM204-EVB with A20-SOM204-1Gs16Me16G-MC Rev.C.

I am trying to get the two ethernet working. So far I was only able to have gmac working (default in the image) or emac enabled instead of gmac (via olinuxino-overlay), but not both emac and gmac.
Since I am not a dts expert, before starting to struggle, I was wondering if someone was already able to write down the right dts for getting both ethernet working.

Thanks in advance.
Best regards,
Vincenzo

[LubOlimex]

We haven't been able to get both Ethernet ports working at the same time ourselves. For the moment we believe that it is not possible to have them working simultaneously. The Allwinner documentation made us believe that it is possible but after a lot of testing we concluded that the documentation is missing to mention some hidden multiplexing. For the moment, you can have either the GbE or the MbE working at a time, you can run script to switch between one or the other.

Of course, you can add external Ethernet to the board via standard communication interface. Maybe the easiest way would be via USB-Ethernet adapter, something like this: https://www.olimex.com/Products/USB-Modules/USB-ETHERNET-AX88772B/

The SOM204-EVB board was made future proof to be compatible with newer chips that have more capabilities, hence there is also USB 3.0 and PCIe connectors (both not supported by Allwinner A20).

[winci45]

Thanks for the prompt reply.
I'm sorry to hear this. Furthermore, the emac interface doesn't even work stably as it hangs after some seconds or minutes of being connected.
I think this info should be clearly written in the product page and, to be honest, I don't see much point in making/selling the -M version at all.

The idea of the SOM204 was quite nice for industrial purposes, but I didn't notice from your blog any future plans for the platform. For instance, a STMP1 version would be make it interesting.

I will think if switching to the A20-SOM or just making some customized "hat" for the A20-OLinuXino-LIME2.

Thanks for the support.
BR,
Vincenzo

[LubOlimex]

Sorry about the confusion, it was never something that we hide, you can see I've mentioned in on few places in the forums and the blog, for example here:

https://www.olimex.com/forum/index.php?topic=7122.0

I've now added it as a FAQ on the SOM204 page.

I think this info should be clearly written in the product page and, to be honest, I don't see much point in making/selling the -M version at all.

It is not terrible to test if either GbE or MbE works better, if a customer seeks stability and not throughput, for example. And stability depends on many factors so emperical test is always a good idea. So for evaluation boards with the -M option make sense.

[winci45]

Thanks for adding the info in the FAQ.
Anyway, I did not manage to make the emac work reliably: the connection is lost after some seconds. I read similar behavior somewhere in the forum.
From this post (https://www.olimex.com/forum/index.php?topic=7720.msg28943#msg28943) it seems the emac worked somehow but with some troubles in the mac address.

I have started working with sunxi hardware (A10) back in 2013 and after 7 years it is still a mess
Thanks for the support.
Br,
Vincenzo

[LubOlimex]

The A20-SOM204 was released after we focused our efforts towards mainline, so the board lacks tested and working sunxi image. So for something working out-of-the-box with A20-SOM204 I'd recommend the mainline images.

However, we made sunxi images for all of the other A20 boards up to that point, and you can use the sources to figure out what might improve the behavior of A20-SOM204, some of the hardware is similar:

https://raw.githubusercontent.com/OLIMEX/OLINUXINO/master/SOFTWARE/A20/A20-build-3.4.103-release-7/BUILD_DESCRIPTION_A20_Olimex_kernel_3.4.103%2B_Jessie_rel_6.txt

It is a good idea to investigate this patch that deals with Ethernet and memories:

https://github.com/OLIMEX/OLINUXINO/blob/master/SOFTWARE/A20/A20-build-3.4.103-release-7/a20-phy_1000_100-dram.patch