Random A13, AXP209 I2C Problem at Startup

[coolbrian]

Hello all,

I am hitting a weird problem.  When my board (A13) starts up, sometimes u-boot spits out:
--
Failed to set core voltage! Can't set CPU frequency
--
which indicates problems with I2C communication to AXP209.  The kernel soon boots and panics
when talking to AXP209.

When this happens, it persists for a while, even after a clean power-on reset.
After a while, this problem just disappears and the board works without noticeable problems.

As I'm googling around, I found this post mentions a similar problem:
https://www.olimex.com/forum/index.php?topic=725.0

But there is no follow-up on the cause or the solution.

I hooked up the scope with the I2C lines and found nothing particularly interesting, except
some tiny glitches on the lines.  When the board boots fine, the glitches are there too.

Are there any known problems/solutions with this AXP209 startup problem?

Any pointers are appreciated.

Thanks in advance.


Brian