[U-Boot] [u-boot]automatic reset of variables to defaults
Jerry Van Baren
gvb.uboot at gmail.com
Thu Nov 17 19:26:58 CET 2011
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
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