Le Potato Ethernet does not work on 10 Mbps mode

[CrushDSS]

HW: Le Potato
Kernel: linux-6.12.y-lc

Ethtool reports that Le Potato supports 100 or 10 Mbps ethernet, but if I try to limit ethernet speed on the Le Potato using:
sudo ethtool -s eth0 speed 10 duplex full autoneg off

it will not connect to router and will not get assigned an IP address.

Similarly if I do not change the Le Potato's ethernet speed, but instead change that the router (running dd-wrt) to only advertise 10 Mbps ethernet, the same issue happens and the Le Potato will not connect. Le Potato will only make a connection if it can make a 100 Mbps connection.

[dsx724]

Does it work on previous kernels? We don't have the hardware to test this.

[dsx724]

You need to play with drivers/net/mdio/mdio-mux-meson-gxl.c line 53. Cross check the datasheet for ETH_REG3. By default, all modes are enabled but there might be a quirk. 10Mb needs to ensure the proper twisted pair is used as well so cabling straight thru or crossover matters.

[CrushDSS]

I just tried quickly on 6.6 and 6.1, in all kernels I am unable to connect to the router in 10 Mbps mode. I don't think you need any special hardware to test, just setting the Le Potato to 10 Mbps mode with the command I specified earlier should suffice.

I am able to connect to the same router and port using same cabling in 10 Mpbs mode using an ESP32 with a W5500 configured and verified working in 10 Mbps, so I don't believe there's any issue with cabling or the router capability.

What datasheet are you referring to? If its S905X datasheet, I can only find revision 0.2 3/14/2017 online, and in it I see no mention of ETH_REG3.

[dsx724]

To be frank I don't think anyone including Amlogic ever tested 10Mb as there is a darth of hardware that still uses it. s905x-eth-mac.pdf

[CrushDSS]

I've toyed around with changing the value of REG3_CFGMODE and it doesn't seem to make any difference, even if I set it to 0x1 device still goes to 100 Mbps speed, both reported by ethtool and testing the actual speed with iperf3. If I try limiting speed again or connecting it to a device that only supports 10 Mbps, once again Le Potato refuses to connect. Is this setting being superseded by something else?

[dsx724]

You have to debug the entire stack from the MAC (dwmac) to the PHY (meson-gxl) with a lot of print statements to figure out exactly what's its doing. Again, 10Mb might have never been tested to work in this IP but the chance of it not working is small but the effort to make it work is large.

[CrushDSS]

I guess I'm less interested in getting 10 Mbps speed working, but more concerned that it is a fallback that should be working. I'm under the impression that switches/routers even if its a Gbps ethernet switch can negotiate down to 10 Mbps when under strain, if ever the Potato goes to 10 Mpbs mode, ethernet becomes non functioning and it won't negotiate itself up to 100 Mbps, requiring manual intervention. Have had intermittent ethernet issues with this device, and suspicious that the non functioning 10 Mbps mode may be playing a part in it.