I played around a bit with this and it is quite strange:

When I reset the board by pressing the reset-button on BBG, on next boot-up 
the Ethernet PHY is working smoothly.

When I do the same programmatically by invoking a cold reset on SoC (by 
writing a 0x02 into reset register 0x44E00F00, the PHY stays in same 
unusable condition. According to TRM of AM335x such a reset should pull 
output NRESETIN_OUT to LOW which should be the same like pressing the 
reset-button.

Any idea why one is working and the other not although they should be the 
same?



Am Samstag, 18. Juni 2016 16:44:20 UTC+2 schrieb Karl Karpfen:
>
> Hi,
>
> I know there is a problem where the Ethernet (PHY?) in some seldom cases 
> isn't initialised properly on power-up ending up in a state where it can't 
> be used and therefore Ethernet is disabled. Now I have a BBG-cape where 
> this happens much more often than I know this from a plain BBB. Two 
> questions on this:
>
> 1. The BBG is powered externally by feeding 5V into VDD. Could a 
> not-so-steep power-on rising edge of VDD make this problem happen more 
> often?
>
> 2. When I'm in this state and press the reset-button on BBG, the problem 
> is solved when the board is back. Is there a possibility to invoke 
> something similar out of software by accessing the PMIC somehow? If yes - 
> what would have to be done?
>
> Thanks and keep the good work going! :-)
>
> Karl
>
>

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