UBootBootCountLimit < DULG

%SECTION0{name=UBootBootCountLimit}% Boot Count Limit

The Open Source Development Labs _Carrier Grade Linux Requirements Definition_
version 2.0
(http://www.osdl.org/docs/carrier_grade_linux_requirements_definition___version_20_final_public_draft.pdf)
contains the following requirement definition (ID PLT.4.0, p. 44):

_CGL shall provide support for detecting a repeating reboot cycle due to recurring failures and will go to an offline state if this occurs._

This feature is available in U-Boot if you enable the ==CONFIG_BOOTCOUNT_LIMIT==
configuration option. The implementation uses the following environment variables:


   *bootcount*:: This variable will be automatically created if it does not exist,
    and it will be updated at each reset of the processor.
    After a power-on reset, it will be initialized with *1*, and each reboot
    will increment the value by *1*. 
   *bootlimit*:: If this variable exists, its contents are taken as the maximum
    number of reboot cycles allowed.
   *altbootcmd*:: If, after a reboot, the new value of ==bootcount==
    exceeds the value of ==bootlimit==, then instead of the standard boot action
    (executing the contents of ==bootcmd==) an alternate boot action will be
    performed, and the contents of ==altbootcmd== will be executed.

If the variable ==bootlimit== is not defined in the environment,
the Boot Count Limit feature is disabled.
If it is enabled, but ==altbootcmd== is not defined, then U-Boot will drop
into interactive mode and remain there.

It is the responsibility of some application code (typically a Linux application)
to reset the variable ==bootcount==, thus allowing for more boot cycles.

%X% At the moment, the Boot Count Limit feature is available only for MPC8xx, MPC82xx and MPC5200 [[PowerPC][Power Architecture]]® processors.
   * [[%ATTACHURL%/ubootBootcountAccess.c][ubootBootcountAccess.c]]: C-source: bootcount access through /proc file system
5.14. U-Boot Advanced Features		1. Abstract		6. Embedded Linux Configuration
Prev		Home		Next