mirror of
https://source.denx.de/u-boot/u-boot.git
synced 2025-10-31 00:11:51 +01:00
fc1383ae2b
- Grammar fixes - Clarify explanations Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com> Reviewed-by: Heiko Schocher <hs@denx.de>
54 lines
1.8 KiB
Plaintext
54 lines
1.8 KiB
Plaintext
.. SPDX-License-Identifier: GPL-2.0+
|
|
|
|
Boot Count Limit
|
|
================
|
|
|
|
This is enabled by CONFIG_BOOTCOUNT_LIMIT.
|
|
|
|
This allows to detect multiple failed attempts to boot Linux.
|
|
|
|
After a power-on reset, the "bootcount" variable will be initialized to 1, and
|
|
each reboot will increment the value by 1.
|
|
|
|
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" to 0 when the system booted
|
|
successfully, thus allowing for more boot cycles.
|
|
|
|
CONFIG_BOOTCOUNT_EXT
|
|
--------------------
|
|
|
|
This adds support for maintaining boot count in a file on an EXT filesystem.
|
|
The file to use is defined by:
|
|
|
|
CONFIG_SYS_BOOTCOUNT_EXT_INTERFACE
|
|
CONFIG_SYS_BOOTCOUNT_EXT_DEVPART
|
|
CONFIG_SYS_BOOTCOUNT_EXT_NAME
|
|
|
|
The format of the file is:
|
|
|
|
==== =================
|
|
type entry
|
|
==== =================
|
|
u8 magic
|
|
u8 version
|
|
u8 bootcount
|
|
u8 upgrade_available
|
|
==== =================
|
|
|
|
To prevent unattended usage of "altbootcmd", the "upgrade_available" variable is
|
|
used.
|
|
If "upgrade_available" is 0, "bootcount" is not saved.
|
|
If "upgrade_available" is 1, "bootcount" is saved.
|
|
So a userspace application should take care of setting the "upgrade_available"
|
|
and "bootcount" variables to 0, if the system boots successfully.
|
|
This also avoids writing the "bootcount" information on all reboots.
|