Boot: Zephyr: Boards: Fix STM32H750B-DK App in Ext Flash support #2479
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…rlay Following the introduction of stm32h750b-dk 'ext_flash_app' board variant, for storing apps in external Flash and chainloading them with MCUboot that's placed in internal Flash, we need a DT overlay to designate internal Flash & controller as the chosen 'zephyr,flash' & 'zephyr,flash-controller' for the MCUboot Zephyr Application. Signed-off-by: Abderrahmane JARMOUNI <[email protected]>
STM32_MEMMAP is no longer needed since it is now set on the Zephyr side in the board's 'Kconfig.defconfig' when building MCUboot app. Also, BOOT_MAX_IMG_SECTORS_AUTO no longer need to be disabled after including the 'soc-nv-flash' binding in the 'st,stm32-qspi-nor' binding, then adding the 'erase-block-size' & 'write-block-size' properties in external Flash DT node. Signed-off-by: Abderrahmane JARMOUNI <[email protected]>
This was referenced Oct 6, 2025
nordicjm
approved these changes
Oct 6, 2025
erwango
reviewed
Oct 7, 2025
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I wonder why this has to be applied to a stm32h750b_dk/stm32h750xx/ext_flash_app target.
My understanding of zephyrproject-rtos/zephyr#97037, is that stm32h750b_dk/stm32h750xx is the target running on internal flash.
This way, we re-use zephyr,flash and zephyr,flash-controller, which are already defined for stm32h750b_dk.dts. And since zephyr,code-partition = &boot_partition; is already defined in app.overlay we don't have any dependency on MCUBoot anymore
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The memory layout for running a user app from external Flash is in ext_flash_app variant dts, and we use stm32h750b_dk/stm32h750xx/ext_flash_app target when building with sysbuild.
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Following the introduction of stm32h750b-dk 'ext_flash_app' board variant (zephyrproject-rtos/zephyr#97037), for storing apps in external Flash and chainloading them with MCUboot that's placed in internal Flash, we need a DT overlay to designate internal Flash & controller as the chosen 'zephyr,flash' & 'zephyr,flash-controller' for the MCUboot Zephyr Application. This way, no DT overlay will be needed at the Zephyr user app level.
Also, remove board conf file, as enabling STM32_MEMMAP is no longer needed here since it is now set on the Zephyr side in the board's 'Kconfig.defconfig' when building MCUboot app. And BOOT_MAX_IMG_SECTORS_AUTO no longer need to be disabled, after including the 'soc-nv-flash' binding in the 'st,stm32-qspi-nor' binding, then adding the 'erase-block-size' & 'write-block-size' properties in external Flash DT node.