I can also confirm having issues with some off the shelf 5V supplies with the EVM and ended up using a 12V supply. My bench supplies are really clean, maybe I'll run a few experiments.
On Sat, Sep 17, 2016 at 11:35 AM, Tony Lindgren tony@atomide.com wrote:
- Michael Mrozek EvilDragon@openpandora.org [160917 07:35]:
Am Wed, 14 Sep 2016 13:49:14 -0700 hat Tony Lindgren tony@atomide.com geschrieben:
Hi Tony and Nikolaus,
okay, I had a little chat with aTc right now, who has a Pyra prototype and also has issues booting it with a stock 5V AC adaptor (and without battery).
I think we made quite a huge step with that issue.
As mentioned, some users at IRC with the EVM don't have any issues with the EVM and more recent kernels.
However, we all switched to using 12V AC adaptors with the EVM, as we ALWAYS had stability issues with 5V adaptors.
I guess both you and Nikolaus are running your EVM with 5V? Then that would be a difference!
Interesting, will need to check the voltage here. I've been slowly rearranging the devices in my rack and it certainly is possible that I've moved my omap5-uevm from 12V input to a 5V input source around May or so.
aTc found some interesting information about that:
page 19 of omap5432-ref-swcu130.pdf: if the input voltage from the jack is below approximately 5.60V, load switch U4 is enabled (driving the main 5V power rail DC_5V with the jack input), and if it is > 5.60V then load switch U18 is enabled (driving the main 5V power rail DC_5V with the SMPS 5V output).
So that means, if you use 5V, you most probably have U4 enabled whereas everyone who runs at 12V has U18 enabled (which uses SMPS 5V output instead of direct Jack input).
It seems to be unstable when running directly from jack input. The igepv5 doesn't have that issue - so something is different here. Could it be that the power is filtered better on the igepv5?
I've always powered igepv5 with 5V input and never had any issues.
What we've found out on the Pyra is that it runs A LOT more stable with a battery. I guess the battery provides a more stable power source than some random USB AC adaptor.
So maybe it's a hardware issue of the EVM, which runs unstable whenever rail DC_5V is powered directly from the input jack and NOT from SMPS 5V output.
It sounds like they forgot to smoothen and filter the power source here, so the better your AC adaptor is, the more stable it runs.
That seems like the best explanation so far :)
Tony _______________________________________________ Kernel mailing list Kernel@pyra-handheld.com http://pyra-handheld.com/cgi-bin/mailman/listinfo/kernel