network: Network auto-negotiation duplex fix for LAN8742

[bkerler]

On auto-negotiation using the external network phy LAN8742, the reference stm32f427 source code incorrectly uses the wrong PHY_SR (status register) addr of 0x10, leading to a false detection of the duplex mode, thus using half-duplex instead of duplex mode, resulting in retransmissions and overall lower throughput of data.

According to the LAN8742a datasheet, page 89, "4.2.22 PHY Special Control/Status Register" the addr is defined as 31 (0x1E), with duplex/half-duplex speed indicator given in bit 4..2.

This patch fixes the duplex mode for the ethernetif.c ... it might be necessary to patch the legacy HAL_ETH_Init as well within the lib/Drivers/STM32F4xx_HAL_Driver/Src/Legacy/stm32f4xx_hal_eth.c.

See further details here as well for reference.

Somewhat related to issue #3049 (not for wifi, but ethernet part)

[ivous]

Hello @bkerler ,
Thank you for your help to improve the Ethernet communication! I have checked proposed fix, but it is not complete unfortunately. There is missing update of other LAN8742 register flags as well. I have tried to finalize from my side and I have reached the state when PHY did connect in full-duplex mode, however the DHCP was not working properly then, which means more changes needs to be done.
The stm32f4xx_hal_eth_legacy.h file, is legacy implementation from STMicroelectronics and since then many updates were done. From my point of view it does not make sense to fix this legacy code , but we need to switch to updated HAL version from STMicroelectronics. We have a plan to do it, however this will take some time to implement.

[bkerler]

@ivous Can you please elaborate which dhcp issues you mean ? I'm using the patch without any issues and can confirm the ethernet connection does work in full-duplex and dhcp works as well.

[bkerler]

This PR has a followup in #4342. As @ivous stated, there were issues that needed to be addressed, thus the followup PR with the upgraded STMF4 Hal as recommended by @ivous :)