mjhjmtu

I'll like to reserved the first 2 GB to the RAM because my hardware write in this position to the memory RAM and I need to the kernel don't touch this part to the memory.

I read to use this option need launch the order memmap in the bootloader and the bootloader to I use is U-Boot because I'm dessing to Driver-Kernel in Yocto OS.

I read this to example to use the memmap:

memmap=nn[KMG]$ss[KMG]
 [KNL,ACPI] Mark specific memory as reserved.
 Region of memory to be reserved is from ss to ss+nn.
 Example: Exclude memory from 0x18690000-0x1869ffff
 memmap=64K$0x18690000
 or
 memmap=0x10000$0x18690000
 Some bootloaders may need an escape character before '$',
 like Grub2, otherwise '$' and the following number
 will be eaten.

And I don't know to use in this case, thankyou

EDIT: New question

I write this option in the U-Boot, using memmap=2G$0x00000000 and memmap=7fffffff$0x00000000, don't return exception,
I guess I write this correctly but in cat / proc / iomem I do not see anything that tells me this memory is reserved for memory.

Would you need to modify .dtb?