. . board/raspberrypi/rpi/rpi.c

/*
 * Prevent relocation from stomping on a firmware provided FDT blob.
 */
1    unsigned long board_get_usable_ram_top(unsigned long total_size)
2    {
3            if ((gd->ram_top - fw_dtb_pointer) > SZ_64M)
4                    return gd->ram_top;
5            return fw_dtb_pointer & ~0xffff;
6    }

.