[PATCH v4 02/10] memblock: Add variables for usable memory limitation

[Rob Herring]

On Wed, Jul 14, 2021 at 02:50:12PM +0200, Geert Uytterhoeven wrote:
> Add two global variables (cap_mem_addr and cap_mem_size) for storing a
> base address and size, describing a limited region in which memory may
> be considered available for use by the kernel.  If enabled, memory
> outside of this range is not available for use.
> 
> These variables can by filled by firmware-specific code, and used in
> calls to memblock_cap_memory_range() by architecture-specific code.
> An example user is the parser of the "linux,usable-memory-range"
> property in the DT "/chosen" node.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas at glider.be>
> ---
> This is similar to how the initial ramdisk (phys_initrd_{start,size})
> and ELF core headers (elfcorehdr_{addr,size})) are handled.
> 
> Does there exist a suitable place in the common memblock code to call
> "memblock_cap_memory_range(cap_mem_addr, cap_mem_size)", or does this
> have to be done in architecture-specific code?

Can't you just call it from early_init_dt_scan_usablemem? If the 
property is present, you want to call it. If the property is not 
present, nothing happens.

Rob