[FS#986] ARV752DPW missing default switch config

[LEDE Bugs]

The following task has a new comment added:

FS#986 - ARV752DPW missing default switch config
User who did this - Oliver Muth (Oliver)

----------
>> root at LEDE:/# rm /etc/board.json
root at LEDE:/# rm /etc/config/network
Yes, this does the trick.

>> This ticket isn't really the right place for tracking this issue

We can take it off-line or into the forum if you want.

>> I was able to use tftp as well as the http recovery interface. 

I am pretty sure that Wireshark did not see a single packet when I tried tftpboot. But I can try that again, when the router is not in use.

>> why the direction change brings the switch back to live (GPIO value of 1 usually releases the reset on my board). 

Yes, according to the RTL8306M datasheet the reset (pin 40) is an active low input. 
They might have added a pull-down resistor to keep the RTL8306M in a safe reset state until the danube drives pin 40 high. In this case making the danube pin an input would be just as good as switching it low.
Or they might have saved a few bucks and not wired any pull-down at all, so that pin 40 would be floating as long as the connected danube pin is an input (Hi-Z).
In any case the connected danube pin should be made an output early in the boot sequence and not be configured as input.

>> The (hard) reset is missing in the lantiq u-boot for the ARV752DPW and will cause a not working u-boot network if you setup vlans in LEDE and do a reboot.

OK, this may explain why I did not have any network at all in u-boot. Of course the box had some vlan config on it, when I took it in order to replace a burnt-up EB 803.

On the ARV752DPW with running LEDE, pin 19 is an input and driven (or pulled) high. Weird. Why input? I will at least try to follow the trace and see where it goes, before I change the GPIO. I don't want to cause smoke signals because I make it an output low, while it is driven high by another chip. ;-)
----------

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=986#comment3380