On 26/03/16 06:20, Michael Haas wrote:

> Hi Iain,
> thanks for the feedback.
> I have yet to try your patch, but I have broken out the multimeter to
> measure LDO3. On GPIO-2, I'm measuring 2.8V between pins 2 and 4 instead
> of 2.3V you seem to measuring.
> In my setup, I have simply removed the SD card from the lime2 to get
> whatever defaults are used at boot.
> How did you measure LDO3? Also, did you find any pins for LDO4 besides
> the AXP209 itelf? Mine seems to be covered in flux.

I measured them at C106 & C107 decoupling caps near the SoC. On my boards 
they're on the bottom, in the square of caps below the SoC, corner nearest 
the uSD card.

LDO3 I also measured at GPIO-2 pins 2 & 4 with a breakout board connected 
as I was concerned that 2.3v at the cap was wrong.

I can easily imagine you might get different values, the datasheet 
has them as undefined after all.  However I'd suggest a power cycle or 
use a version of u-boot from before the patches went in to set LDO3/4 
to 2.8v. Soft reboot or such like probably leaves the values previously 
programmed by whatever last touched them.

Even then, different batch of AXP209, or a different boot0 in the A20 
could lead to different results.  The danger is that we're missing 
some piece of information that means there's no safe way to turn these 
regulators off then back on without the lockup. Suggest that if you do 
get different results from me, then it's even more likely we don't know 
what's going on and something that works on my board may not on yours.

Anyway, you probably want to read my second follow up. Turning these off 
is the wrong thing to do regardless. The inputs to the SoC are mis-labeled 
in the schematics, disabling them disables all io pins in groups E & G 
whether they're configured for CSI tasks or not.


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