drivers: flash: stm32 xspi flash read with memcopy when executing

[FRASTM]

When the application is executed in external flash, the read operation cannot be in indirect mode but with memcopy.
When executing in external flash, the CONFIG_STM32_APP_IN_EXT_FLASH is set, the application knows the external flash reading is done with memcopy.

Note that writing or erasing the external flash being executed is not possible during the execution on the external flash.

Fixes #92883

[FRASTM]

run the samples/sysbuild/with_mcuboot/ on the stm32h573i_dk with --sysbuild and mcuboot shell :

CONFIG_SHELL=y
CONFIG_FLASH_SHELL=y
CONFIG_BOOTLOADER_MCUBOOT=y
CONFIG_MCUBOOT_SHELL=y
CONFIG_IMG_MANAGER=y
CONFIG_STREAM_FLASH=y
CONFIG_MCUBOOT_IMG_MANAGER=y

*** Booting Zephyr OS build v4.2.0-678-g399f8f8b181f ***
Address of sample 0x90000000
Hello sysbuild with mcuboot! stm32h573i_dk
uart:~$ mcuboot
swap type: none
confirmed: 1

primary area (2):
  version: 0.0.0+0
  image size: 76984
  magic: unset
  swap type: none
  copy done: unset
  image ok: unset

secondary area (3):
  version: 0.0.0+0
  image size: 78008
  magic: unset
  swap type: none
  copy done: unset                                                                                                   
  image ok: unset                                                                                                    
[00:00:04.089,000] <inf> mcuboot_util: Image index: 0, Swap type: none                                               
uart:~$ 

(with a second image downloaded on slot1_partition)

[FRASTM]

same change to apply to the

• ./drivers/flash/flash_stm32_ospi
• ./drivers/flash/flash_stm32_qspi

when reading with the CONFIG_STM32_APP_IN_EXT_FLASH set

[JarmouniA]

Suggested change

	#if defined(CONFIG_STM32_MEMMAP) || defined(CONFIG_STM32_APP_IN_EXT_FLASH)
	#if defined(CONFIG_STM32_MEMMAP) || (defined(CONFIG_STM32_APP_IN_EXT_FLASH) && defined(CONFIG_XIP))

This is needed in my opinion, since the app image can be stored in ext flash but then be executed in RAM (after being copied there by MCUboot). In that case, we are not sure if the Flash is still MemMapped, because the app can exit Memmap mode and use a storage partition in external Flash for ex. Does this make sense?

zephyr/share/sysbuild/image_configurations/MAIN_image_default.cmake

Line 40 in 00e217d

set_config_bool(${ZCMAKE_APPLICATION} CONFIG_XIP n)

But maybe CONFIG_XIP is not the appropriate flag to check, since it is not disabled in SINGLE_APP_RAM_LOAD mode for ex.

zephyr/share/sysbuild/image_configurations/MAIN_image_default.cmake

Line 42 in 00e217d

elseif(SB_CONFIG_MCUBOOT_MODE_SINGLE_APP_RAM_LOAD)

I'm no longer sure of the exact semantics of Zephyr XiP at this point, I think it just means "app is executed where it was last loaded, RAM, Flash, PSRAM...by either flashloader or bootloader" or something close to this.

@nordicjm Any thoughts on this? what am I getting wrong?

[FRASTM]

waiting for @nordicjm comment

[JarmouniA]

We will perhaps need to check for MCUboot modes instead, to know if Memmap mode is still required after the image has started executing, see #85254 (comment)

It appears that XiP semantics in Zephyr needs real clarification in the docs & Kconfig help text, especially in relationship to the usage of a bootloader that can move the app image around, and Zephyr Code Relocation as well.

[nordicjm]

to be honest I think the comment about single loader is wrong, it is executing from RAM, it should have XIP set to n, XIP means running from flash, the help text is clear on that:

        help
          This option allows the kernel to operate with its text and read-only
          sections residing in ROM (or similar read-only memory). Not all boards
          support this option so it must be used with care; you must also
          supply a linker command file when building your image. Enabling this
          option increases both the code and data footprint of the image.

[JarmouniA]

XIP means running from flash, the help text is clear on that

But is the help text still accurate today, compared to when XiP was first introduced?

[nordicjm]

XIP means running from flash, the help text is clear on that

But is the help text still accurate today, compared to when XiP was first introduced?

yes, you are still running from read only media (one could argue that you could erase the flash sector you are running meaning it's not read only but that's not going to go well)

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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