[U-Boot] [u-boot]automatic reset of variables to defaults

[Jerry Van Baren <gvb.uboot@gmail.com>]

On 11/17/2011 10:46 AM, Dennis Borgmann wrote:
> Hello u-boot users list,
>
> I am experiencing a problem concerning variables being set and later
> getting lost.

This sounds like your environment variables in flash got erased or 
corrupted.  The question is why.

Where is your u-boot env being saved?  Normal flash?  I2C-attached 
flash?  Other?  (I2C flash is inherently less robust than we like due to 
weaknesses in the protocol.)

I am assuming normal flash...
* Do you have flash write protection enabled (prevents inadvertent flash 
scribbling, especially a problem if your linux or programs are not stable).

* Do you understand your flash memory layout (can you draw a diagram of 
it)?  Is something like a flash file system inadvertently overlayed on 
top of the u-boot env?  If you have a flash file system inadvertently 
configured to use the same memory space as your u-boot env, it will 
"randomly" overwrite it based on file activity.

* Do you use linux utilities to read/write your u-boot env?

When the failure occurs, what does the memory dump of the actual u-boot 
flash storage area look like?  Quite often the overwrite pattern leaves 
valuable clues as to who did it.

* If it is all 0xFF, someone just erased it.

* If some bits are set to zero that should be ones, someone probably did 
an inadvertent write to the memory (writing a '0' to a '1' bit turns it 
to a '0', writing a '0' or '1' to a '0' bit doesn't change it).

* Does it look like file data?

[snip]

> Annoyingly, I cannot surely reproduce this error. I tried rebooting it
> over 3 days in 2-minute-steps and the error won't occur. In addition, I
> tried giving random input to the console of u-boot for 3 days (again in
> 2-minute-steps) and still the error won't come up.

We've all been there and feel your pain. :-(

> Two questions:
>
> 1. What else might be the cause of this?

Someone (likely software, possibly hardware) is corrupting or erasing 
your u-boot env storage in flash.

> 2. How could I prevent u-boot from resetting to its default value?

Fix whoever is doing the scribbling.  There is no other way.

> I'd be happy for any kind of help.
>
> Best regards,
> Dennis

Good luck,
gvb