Store variables in flash at compile time

[y009]

Hello I am using I am NRF SDK version 1.8.0 and nrf-zephyr v2.7.0-ncs1 (If a soultion exists on newer a rev, willing to upgrade now, otherwise it will happen some time in the future)
and I am looking for a good way to store factory settings on nrf9160 devices. 

I figured I'd make a separate storage partition that would be read only to the application and would be populated at compile time. 

I did find this support post:
How to store constant variables at specific address during compile time

Though the post is 6 years old now, and I'm wondering if there is perhaps a better way to do this using using ncs and wests tools
(should direct this more towards zephyr dev community?)

[Priyanka]

Hi Henry,

The post that you mentioned was for baremetal and with softdevice. With the nRF Connect SDK, you can create a new partition accessible for the application. I guess you need to give the partition data in yml file. You need to use partition manager pm_static.yml to configure what you wish. You can refer this documentation as a starting point.

Best Regards,

Priyanka

[y009]

Sorry for the late reply (probably shouldnt have asked before going on vacation).

I looked the PM before a little bit, also, and hopefully made it clear to myself.
To check:
By default the $BUILD_DIR/partitions.yml for nrf9160 has EMPTY_0, -1 and -2, which look like prime real-estate for me.

EMPTY_0:
  address: 0xc000
  end_address: 0x10000
  placement:
    before:
    - mcuboot_pad
  region: flash_primary
  size: 0x4000
EMPTY_1:
  address: 0xfe000
  end_address: 0x100000
  placement:
    after:
    - littlefs_storage
  region: flash_primary
  size: 0x2000
EMPTY_2:
  address: 0xf0000
  end_address: 0xf8000
  placement:
    after:
    - mcuboot_secondary
  region: flash_primary
  size: 0x8000
app:
  address: 0x20200
  end_address: 0x80000
  region: flash_primary
  size: 0x5fe00
littlefs_storage:
  address: 0xf8000
  end_address: 0xfe000
  placement:
    align:
      start: 0x8000
    before:
    - end
  region: flash_primary
  size: 0x6000
mcuboot:
  address: 0x0
  end_address: 0xc000
  placement:
    before:
    - mcuboot_primary
  region: flash_primary
  size: 0xc000
mcuboot_pad:
  address: 0x10000
  end_address: 0x10200
  placement:
    align:
      start: 0x8000
    before:
    - mcuboot_primary_app
  region: flash_primary
  size: 0x200
mcuboot_primary:
  address: 0x10000
  end_address: 0x80000
  orig_span: &id001
  - mcuboot_pad
  - spm
  - app
  region: flash_primary
  sharers: 0x1
  size: 0x70000
  span: *id001
mcuboot_primary_app:
  address: 0x10200
  end_address: 0x80000
  orig_span: &id002
  - app
  - spm
  region: flash_primary
  size: 0x6fe00
  span: *id002
mcuboot_secondary:
  address: 0x80000
  end_address: 0xf0000
  placement:
    after:
    - mcuboot_primary
    align:
      start: 0x8000
  region: flash_primary
  share_size:
  - mcuboot_primary
  size: 0x70000
nrf_modem_lib_ctrl:
  address: 0x20010000
  end_address: 0x200104e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - spm_sram
    - start
  region: sram_primary
  size: 0x4e8
nrf_modem_lib_rx:
  address: 0x200124e8
  end_address: 0x200144e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - nrf_modem_lib_tx
  region: sram_primary
  size: 0x2000
nrf_modem_lib_sram:
  address: 0x20010000
  end_address: 0x200144e8
  orig_span: &id003
  - nrf_modem_lib_ctrl
  - nrf_modem_lib_tx
  - nrf_modem_lib_rx
  region: sram_primary
  size: 0x44e8
  span: *id003
nrf_modem_lib_tx:
  address: 0x200104e8
  end_address: 0x200124e8
  inside:
  - sram_nonsecure
  placement:
    after:
    - nrf_modem_lib_ctrl
  region: sram_primary
  size: 0x2000
otp:
  address: 0xff8108
  end_address: 0xff83fc
  region: otp
  size: 0x2f4
spm:
  address: 0x10200
  end_address: 0x20200
  inside:
  - mcuboot_primary_app
  placement:
    before:
    - app
  region: flash_primary
  size: 0x10000
spm_sram:
  address: 0x20000000
  end_address: 0x20010000
  inside:
  - sram_secure
  placement:
    after:
    - start
  region: sram_primary
  size: 0x10000
sram_nonsecure:
  address: 0x20010000
  end_address: 0x20040000
  orig_span: &id004
  - sram_primary
  - nrf_modem_lib_ctrl
  - nrf_modem_lib_tx
  - nrf_modem_lib_rx
  region: sram_primary
  size: 0x30000
  span: *id004
sram_primary:
  address: 0x200144e8
  end_address: 0x20040000
  region: sram_primary
  size: 0x2bb18
sram_secure:
  address: 0x20000000
  end_address: 0x20010000
  orig_span: &id005
  - spm_sram
  region: sram_primary
  size: 0x10000
  span: *id005

Changing for example empty_1 to my setting area
pm_static.yml:

EMPTY_0:
  address: 0xc000
  end_address: 0x10000
  placement:
    before:
    - mcuboot_pad
  region: flash_primary
  size: 0x4000
EMPTY_1:
  address: 0xf0000
  end_address: 0xf8000
  placement:
    after:
    - mcuboot_secondary
  region: flash_primary
  size: 0x8000
settings:
  address: 0xfe000
  end_address: 0x100000
  placement:
    after:
    - littlefs_storage
  region: flash_primary
  size: 0x2000
app:
...
...
...

Should be ok?

Though Im confused about the dts definitions still.
Do I have to change them for my board?
The generated .yml and the dts dont quite add up, or is it OK to leave it as is?
 

&flash0 {

	partitions {
		compatible = "fixed-partitions";
		#address-cells = <1>;
		#size-cells = <1>;

		boot_partition: partition@0 {
			label = "mcuboot";
			reg = <0x00000000 0x10000>;
		};
		slot0_partition: partition@10000 {
			label = "image-0";
		};
		slot0_ns_partition: partition@50000 {
			label = "image-0-nonsecure";
		};
		slot1_partition: partition@80000 {
			label = "image-1";
		};
		slot1_ns_partition: partition@c0000 {
			label = "image-1-nonsecure";
		};
		scratch_partition: partition@f0000 {
			label = "image-scratch";
			reg = <0x000f0000 0xa000>;
		};
		storage_partition: partition@fa000 {
			label = "storage";
			reg = <0x000fa000 0x00006000>;
		};
	};
};

[y009]

Hopefully i've been moving in the right direction.
I modified my boards dts as:

		storage_partition: partition@fa000 {
			label = "storage";
			reg = <0x000fa000 0x00004000>;
		};

		settings_partition: partition@fe000 {
			label = "settings";
			reg = <0x000fe000 0x00002000>;
		};

And based on /samples/application_development/code_relocation_nocopy/ 
I've been trying to move it to my defined partition but to no avail.

In my cmakelist I added the code relocate as:

    target_sources(app PRIVATE ${app_sources})
    target_sources_ifdef(true app PRIVATE linker_arm_nocopy.ld)
    zephyr_code_relocate(src/hw_settings.c EXTFLASH) # move settings to correct partition

I copied the linker code from <arch/arm/aarch32/cortex_m/scripts/linker.ld> to linker_arm_nocopy:

/*
 * Copyright (c) 2013-2014 Wind River Systems, Inc.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @file
 * @brief Linker command/script file
 *
 * Linker script for the Cortex-M platforms.
 */

#include <autoconf.h>
#include <linker/sections.h>
#include <devicetree.h>

#include <linker/devicetree_regions.h>
#include <linker/linker-defs.h>
#include <linker/linker-tool.h>

/* physical address of RAM */
#ifdef CONFIG_XIP
#define ROMABLE_REGION FLASH
#define RAMABLE_REGION SRAM
#else
#define ROMABLE_REGION SRAM
#define RAMABLE_REGION SRAM
#endif

#if USE_PARTITION_MANAGER

#include <pm_config.h>

#ifdef LINK_INTO_s1
/* We are linking against S1, create symbol containing the flash ID of S0.
 * This is used when writing code operating on the "other" slot.
 */
_image_1_primary_slot_id = PM_S0_ID;

#define ROM_ADDR PM_ADDRESS + PM_S1_ADDRESS - PM_S0_ADDRESS

#else /* ! LINK_INTO_s1 */

#ifdef PM_S1_ID
/* We are linking against S0, create symbol containing the flash ID of S1.
 * This is used when writing code operating on the "other" slot.
 */
_image_1_primary_slot_id = PM_S1_ID;
#endif /* PM_S1_ID */

#define ROM_ADDR PM_ADDRESS
#endif /* LINK_MCUBOOT_INTO_s1 */
#define ROM_SIZE PM_SIZE

#define RAM_SIZE PM_SRAM_SIZE
#define RAM_ADDR PM_SRAM_ADDRESS

#else /* ! USE_PARTITION_MANAGER */

#if !defined(CONFIG_XIP) && (CONFIG_FLASH_SIZE == 0)
#define ROM_ADDR RAM_ADDR
#else
#define ROM_ADDR (CONFIG_FLASH_BASE_ADDRESS + CONFIG_FLASH_LOAD_OFFSET)
#endif

#if CONFIG_FLASH_LOAD_SIZE > 0
#define ROM_SIZE CONFIG_FLASH_LOAD_SIZE
#else
#define ROM_SIZE (CONFIG_FLASH_SIZE*1K - CONFIG_FLASH_LOAD_OFFSET)
#endif

#if defined(CONFIG_XIP)
#if defined(CONFIG_IS_BOOTLOADER)
#define RAM_SIZE (CONFIG_BOOTLOADER_SRAM_SIZE * 1K)
#define RAM_ADDR (CONFIG_SRAM_BASE_ADDRESS + \
	(CONFIG_SRAM_SIZE * 1K - RAM_SIZE))
#else
#define RAM_SIZE (CONFIG_SRAM_SIZE * 1K)
#define RAM_ADDR CONFIG_SRAM_BASE_ADDRESS
#endif
#else
#define RAM_SIZE (CONFIG_SRAM_SIZE * 1K - CONFIG_BOOTLOADER_SRAM_SIZE * 1K)
#define RAM_ADDR CONFIG_SRAM_BASE_ADDRESS
#endif

#endif /* USE_PARTITION_MANAGER */

#if DT_NODE_HAS_STATUS(DT_CHOSEN(zephyr_ccm), okay)
#define CCM_SIZE DT_REG_SIZE(DT_CHOSEN(zephyr_ccm))
#define CCM_ADDR DT_REG_ADDR(DT_CHOSEN(zephyr_ccm))
#endif

#if DT_NODE_HAS_STATUS(DT_CHOSEN(zephyr_itcm), okay)
#define ITCM_SIZE DT_REG_SIZE(DT_CHOSEN(zephyr_itcm))
#define ITCM_ADDR DT_REG_ADDR(DT_CHOSEN(zephyr_itcm))
#endif

#if DT_NODE_HAS_STATUS(DT_CHOSEN(zephyr_dtcm), okay)
#define DTCM_SIZE DT_REG_SIZE(DT_CHOSEN(zephyr_dtcm))
#define DTCM_ADDR DT_REG_ADDR(DT_CHOSEN(zephyr_dtcm))
#endif

#if defined(CONFIG_CUSTOM_SECTION_ALIGN)
_region_min_align = CONFIG_CUSTOM_SECTION_MIN_ALIGN_SIZE;
#else
/* Set alignment to CONFIG_ARM_MPU_REGION_MIN_ALIGN_AND_SIZE
 * to make linker section alignment comply with MPU granularity.
 */
#if defined(CONFIG_ARM_MPU_REGION_MIN_ALIGN_AND_SIZE)
_region_min_align = CONFIG_ARM_MPU_REGION_MIN_ALIGN_AND_SIZE;
#else
/* If building without MPU support, use default 4-byte alignment. */
_region_min_align = 4;
#endif
#endif

#if !defined(CONFIG_CUSTOM_SECTION_ALIGN) && defined(CONFIG_MPU_REQUIRES_POWER_OF_TWO_ALIGNMENT)
#define MPU_ALIGN(region_size) \
    . = ALIGN(_region_min_align); \
    . = ALIGN( 1 << LOG2CEIL(region_size))
#else
#define MPU_ALIGN(region_size) \
    . = ALIGN(_region_min_align)
#endif

MEMORY
    {
    FLASH (rx) : ORIGIN = ROM_ADDR, LENGTH = ROM_SIZE - 0x2000
    SRAM  (wx) : ORIGIN = RAM_ADDR, LENGTH = RAM_SIZE
    EXTFLASH (wx) : ORIGIN = 0xfe000, LENGTH = 0x2000

    /* TI CCFG Registers */
    LINKER_DT_REGION_FROM_NODE(FLASH_CCFG, rwx, DT_NODELABEL(ti_ccfg_partition))
    /* Data & Instruction Tightly Coupled Memory */
    LINKER_DT_REGION_FROM_NODE(ITCM, rw, DT_CHOSEN(zephyr_itcm))
    LINKER_DT_REGION_FROM_NODE(DTCM, rw, DT_CHOSEN(zephyr_dtcm))
    /* STM32 Core Coupled Memory */
    LINKER_DT_REGION_FROM_NODE(CCM, rw, DT_CHOSEN(zephyr_ccm))
    /* STM32WB IPC RAM */
    LINKER_DT_REGION_FROM_NODE(SRAM1, rw, DT_NODELABEL(sram1))
    LINKER_DT_REGION_FROM_NODE(SRAM2, rw, DT_NODELABEL(sram2))
    /* STM32 alternate RAM configurations */
    LINKER_DT_REGION_FROM_NODE(SRAM3, rw, DT_NODELABEL(sram3))
    LINKER_DT_REGION_FROM_NODE(SRAM4, rw, DT_NODELABEL(sram4))
    LINKER_DT_REGION_FROM_NODE(SDRAM1, rw, DT_NODELABEL(sdram1))
    LINKER_DT_REGION_FROM_NODE(SDRAM2, rw, DT_NODELABEL(sdram2))
    LINKER_DT_REGION_FROM_NODE(BACKUP_SRAM, rw, DT_NODELABEL(backup_sram))
    /* Used by and documented in include/linker/intlist.ld */
    IDT_LIST (wx) : ORIGIN = 0xFFFFF7FF, LENGTH = 2K
    }

ENTRY(CONFIG_KERNEL_ENTRY)

SECTIONS
    {

#include <linker/rel-sections.ld>

    /*
     * .plt and .iplt are here according to 'arm-zephyr-elf-ld --verbose',
     * before text section.
     */
    /DISCARD/ :
	{
	*(.plt)
	}

    /DISCARD/ :
	{
	*(.iplt)
	}

    GROUP_START(ROMABLE_REGION)

	__rom_region_start = ROM_ADDR;

    SECTION_PROLOGUE(rom_start,,)
	{

/* Located in generated directory. This file is populated by calling
 * zephyr_linker_sources(ROM_START ...). This typically contains the vector
 * table and debug information.
 */
#include <snippets-rom-start.ld>

	} GROUP_LINK_IN(ROMABLE_REGION)

#ifdef CONFIG_CODE_DATA_RELOCATION

#include <linker_relocate.ld>

#endif /* CONFIG_CODE_DATA_RELOCATION */

    SECTION_PROLOGUE(_TEXT_SECTION_NAME,,)
	{
	__text_region_start = .;

#include <linker/kobject-text.ld>

	*(.text)
	*(".text.*")
	*(".TEXT.*")
	*(.gnu.linkonce.t.*)

	/*
	 * These are here according to 'arm-zephyr-elf-ld --verbose',
	 * after .gnu.linkonce.t.*
	 */
	*(.glue_7t) *(.glue_7) *(.vfp11_veneer) *(.v4_bx)

	} GROUP_LINK_IN(ROMABLE_REGION)

	__text_region_end = .;

#if defined (CONFIG_CPLUSPLUS)
	SECTION_PROLOGUE(.ARM.extab,,)
	{
	/*
	 * .ARM.extab section containing exception unwinding information.
	 */
	*(.ARM.extab* .gnu.linkonce.armextab.*)
	} GROUP_LINK_IN(ROMABLE_REGION)
#endif

	SECTION_PROLOGUE(.ARM.exidx,,)
	{
	/*
	 * This section, related to stack and exception unwinding, is placed
	 * explicitly to prevent it from being shared between multiple regions.
	 * It  must be defined for gcc to support 64-bit math and avoid
	 * section overlap.
	 */
	__exidx_start = .;
#if defined (__GCC_LINKER_CMD__)
	*(.ARM.exidx* gnu.linkonce.armexidx.*)
#endif
	__exidx_end = .;
	} GROUP_LINK_IN(ROMABLE_REGION)

	__rodata_region_start = .;

#include <linker/common-rom.ld>
#include <linker/thread-local-storage.ld>

    SECTION_PROLOGUE(_RODATA_SECTION_NAME,,)
	{
	*(.rodata)
	*(".rodata.*")
	*(.gnu.linkonce.r.*)

/* Located in generated directory. This file is populated by the
 * zephyr_linker_sources() Cmake function.
 */
#include <snippets-rodata.ld>

#include <linker/kobject-rom.ld>

	/*
	 * For XIP images, in order to avoid the situation when __data_rom_start
	 * is 32-bit aligned, but the actual data is placed right after rodata
	 * section, which may not end exactly at 32-bit border, pad rodata
	 * section, so __data_rom_start points at data and it is 32-bit aligned.
	 *
	 * On non-XIP images this may enlarge image size up to 3 bytes. This
	 * generally is not an issue, since modern ROM and FLASH memory is
	 * usually 4k aligned.
	 */
	. = ALIGN(4);
	} GROUP_LINK_IN(ROMABLE_REGION)

#include <linker/cplusplus-rom.ld>

	__rodata_region_end = .;
	MPU_ALIGN(__rodata_region_end -__rom_region_start);
	__rom_region_end = .;

    GROUP_END(ROMABLE_REGION)

    /*
     * These are here according to 'arm-zephyr-elf-ld --verbose',
     * before data section.
     */
    /DISCARD/ : {
	*(.got.plt)
	*(.igot.plt)
	*(.got)
	*(.igot)
	}

    GROUP_START(RAMABLE_REGION)

	. = RAM_ADDR;
	/* Align the start of image SRAM with the
	 * minimum granularity required by MPU.
	 */
	. = ALIGN(_region_min_align);
	_image_ram_start = .;

/* Located in generated directory. This file is populated by the
 * zephyr_linker_sources() Cmake function.
 */
#include <snippets-ram-sections.ld>

#if defined(CONFIG_USERSPACE)
#define APP_SHARED_ALIGN . = ALIGN(_region_min_align);
#define SMEM_PARTITION_ALIGN MPU_ALIGN

#include <app_smem.ld>

	_app_smem_size = _app_smem_end - _app_smem_start;
	_app_smem_rom_start = LOADADDR(_APP_SMEM_SECTION_NAME);

    SECTION_DATA_PROLOGUE(_BSS_SECTION_NAME,(NOLOAD),)
	{
        /*
         * For performance, BSS section is assumed to be 4 byte aligned and
         * a multiple of 4 bytes
         */
        . = ALIGN(4);
	__bss_start = .;
	__kernel_ram_start = .;

	*(.bss)
	*(".bss.*")
	*(COMMON)
	*(".kernel_bss.*")

#ifdef CONFIG_CODE_DATA_RELOCATION
#include <linker_sram_bss_relocate.ld>
#endif

        /*
         * As memory is cleared in words only, it is simpler to ensure the BSS
         * section ends on a 4 byte boundary. This wastes a maximum of 3 bytes.
		 */
	__bss_end = ALIGN(4);
	} GROUP_DATA_LINK_IN(RAMABLE_REGION, RAMABLE_REGION)

#include <linker/common-noinit.ld>

#endif  /* CONFIG_USERSPACE */

    GROUP_START(DATA_REGION)

    SECTION_DATA_PROLOGUE(_DATA_SECTION_NAME,,)
	{
	__data_region_start = .;
	__data_start = .;
	*(.data)
	*(".data.*")
	*(".kernel.*")

/* Located in generated directory. This file is populated by the
 * zephyr_linker_sources() Cmake function.
 */
#include <snippets-rwdata.ld>

#ifdef CONFIG_CODE_DATA_RELOCATION
#include <linker_sram_data_relocate.ld>
#endif
	__data_end = .;

	} GROUP_DATA_LINK_IN(RAMABLE_REGION, ROMABLE_REGION)
    __data_size = __data_end - __data_start;
    __data_load_start = LOADADDR(_DATA_SECTION_NAME);

    __data_region_load_start = LOADADDR(_DATA_SECTION_NAME);

#include <linker/common-ram.ld>
#include <linker/kobject-data.ld>

#include <linker/cplusplus-ram.ld>

/* Located in generated directory. This file is populated by the
 * zephyr_linker_sources() Cmake function.
 */
#include <snippets-data-sections.ld>

    __data_region_end = .;

#ifndef CONFIG_USERSPACE
   SECTION_DATA_PROLOGUE(_BSS_SECTION_NAME,(NOLOAD),)
	{
        /*
         * For performance, BSS section is assumed to be 4 byte aligned and
         * a multiple of 4 bytes
         */
        . = ALIGN(4);
	__bss_start = .;
	__kernel_ram_start = .;

	*(.bss)
	*(".bss.*")
	*(COMMON)
	*(".kernel_bss.*")

#ifdef CONFIG_CODE_DATA_RELOCATION
#include <linker_sram_bss_relocate.ld>
#endif

        /*
         * As memory is cleared in words only, it is simpler to ensure the BSS
         * section ends on a 4 byte boundary. This wastes a maximum of 3 bytes.
		 */
	__bss_end = ALIGN(4);
	} GROUP_DATA_LINK_IN(RAMABLE_REGION, RAMABLE_REGION)

    SECTION_PROLOGUE(_NOINIT_SECTION_NAME,(NOLOAD),)
        {
        /*
         * This section is used for non-initialized objects that
         * will not be cleared during the boot process.
         */
        *(.noinit)
        *(".noinit.*")
	*(".kernel_noinit.*")

/* Located in generated directory. This file is populated by the
 * zephyr_linker_sources() Cmake function.
 */
#include <snippets-noinit.ld>

        } GROUP_LINK_IN(RAMABLE_REGION)
#endif /* CONFIG_USERSPACE */

    /* Define linker symbols */

    _image_ram_end = .;
    _end = .; /* end of image */

    __kernel_ram_end = RAM_ADDR + RAM_SIZE;
    __kernel_ram_size = __kernel_ram_end - __kernel_ram_start;

    GROUP_END(RAMABLE_REGION)

#if DT_NODE_HAS_STATUS(DT_CHOSEN(zephyr_itcm), okay)
GROUP_START(ITCM)

	SECTION_PROLOGUE(_ITCM_SECTION_NAME,,SUBALIGN(4))
	{
		__itcm_start = .;
		*(.itcm)
		*(".itcm.*")
		__itcm_end = .;
	} GROUP_LINK_IN(ITCM AT> ROMABLE_REGION)

	__itcm_size = __itcm_end - __itcm_start;
	__itcm_load_start = LOADADDR(_ITCM_SECTION_NAME);

GROUP_END(ITCM)
#endif

#if DT_NODE_HAS_STATUS(DT_CHOSEN(zephyr_dtcm), okay)
GROUP_START(DTCM)

	SECTION_PROLOGUE(_DTCM_BSS_SECTION_NAME, (NOLOAD),SUBALIGN(4))
	{
		__dtcm_start = .;
		__dtcm_bss_start = .;
		*(.dtcm_bss)
		*(".dtcm_bss.*")
		__dtcm_bss_end = .;
	} GROUP_LINK_IN(DTCM)

	SECTION_PROLOGUE(_DTCM_NOINIT_SECTION_NAME, (NOLOAD),SUBALIGN(4))
	{
		__dtcm_noinit_start = .;
		*(.dtcm_noinit)
		*(".dtcm_noinit.*")
		__dtcm_noinit_end = .;
	} GROUP_LINK_IN(DTCM)

	SECTION_PROLOGUE(_DTCM_DATA_SECTION_NAME,,SUBALIGN(4))
	{
		__dtcm_data_start = .;
		*(.dtcm_data)
		*(".dtcm_data.*")
		__dtcm_data_end = .;
	} GROUP_LINK_IN(DTCM AT> ROMABLE_REGION)

	__dtcm_end = .;

	__dtcm_data_load_start = LOADADDR(_DTCM_DATA_SECTION_NAME);

GROUP_END(DTCM)
#endif

/* Located in generated directory. This file is populated by the
 * zephyr_linker_sources() Cmake function.
 */
#include <snippets-sections.ld>

#include <linker/debug-sections.ld>

    /DISCARD/ : { *(.note.GNU-stack) }

    SECTION_PROLOGUE(.ARM.attributes, 0,)
	{
	KEEP(*(.ARM.attributes))
	KEEP(*(.gnu.attributes))
	}

/* Must be last in romable region */
SECTION_PROLOGUE(.last_section,(NOLOAD),)
{
} GROUP_LINK_IN(ROMABLE_REGION)

/* To provide the image size as a const expression,
 * calculate this value here. */
_flash_used = LOADADDR(.last_section) - __rom_region_start;

    }

changing the MEMORY section to try to accomodate for my partition:

FLASH (rx) : ORIGIN = ROM_ADDR, LENGTH = ROM_SIZE - 0x2000
SRAM (wx) : ORIGIN = RAM_ADDR, LENGTH = RAM_SIZE
EXTFLASH (wx) : ORIGIN = 0xfe000, LENGTH = 0x2000

The hw_settings.c file im trying to test with:

#include <stdint.h>

const uint32_t var_ext_settings = 666U; 

void function_in_ext_flash(void)
{
	printk("Address of %s %p\n", __func__, &function_in_ext_flash);
	printk("Address of var_ext_sram_data %p (%d)\n", &var_ext_settings, var_ext_settings);
}

Building it show some memory getting used 
EXTFLASH:         160 B         8 KB      1.95%

But currently I'm getting a boot loop with a message:

 Non-secure callable region 0 placed in flash region 3 with size 32.

Changing the cmakelist file to only EXTFLASH_DATA, doesn't result in this behaviour, but the data is still in the main app memory region and the generated code_relocation.c file has empty functions:

void data_copy_xip_relocation(void)
{
void;
}

void bss_zeroing_relocation(void)
{
return;
}

And memory region after buillding shows  
EXTFLASH:          0 GB         8 KB      0.00%

Any suggestions would be highly appreciated.

[y009]

In last message i said "Changing the cmakelist file to only EXTFLASH_DATA, doesn't result in this behaviour..." It does actually result in the same loop. I must have been flashing something else.