[U-Boot] Query regarding Uboot Bootcount save in RAM

[Manas Marwah]

Hi,



I am trying to understand the uboot support to store the bootcount in RAM
and working on aarch64 platform.



Relevant configuration:

1.       CONFIG_BOOTCOUNT_LIMIT

2.       CONFIG_BOOTCOUNT_RAM

3.       BOOTCOUNT_ADDR <RAM address>



Relevant code:

drivers/bootcount/bootcount_ram.c



>From the code it is clear along with bootcount, uboot writes a MAGIC number
and a  BIG pattern.



*Memory writing pattern in Uboot: *(In unsigned long: 8 bytes)



<Bootcount><MAGIC
Number><void><Pattern1><Pattern2><Pattern3><Pattern4><Pattern5>…… Pattern *
1000 times



So effectively to save a counter we would need: 8 (Bootcount) + 8 (MAGIC
Number) + 8 (void) + (8*1000) BIG PATTERN => 8024 bytes  => ~8KB contiguous
reserved memory in RAM.





*Queries*:

1.       If, I reduce the REPEAT times for pattern from 1000 to 100 the
only consequence I see is the reduction in possibility of detecting bit
errors.

a.       Do you see any other consequence if I reduce REPEAT times for
pattern?



2.       While reading the boot count Uboot always fail in pattern checking
and reverts the bootcount to 0.

a.       It seems a *bug* to me in bootcount_ram.c line 59 where comparison
between tmp and pattern[1] (0xFFFFFFFF) always fails.
                             b.      It works well with cast “if (tmp !=
*(int)* patterns[i % NBR_OF_PATTERNS])”

-- 
Thanks & Regards,
Manas Marwah