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boot: zephyr: kconfig: Default to swap using offset for nRF devices #2266

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boot: zephyr: kconfig: Default to swap using offset for nRF devices #2266

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2 changes: 1 addition & 1 deletion boot/zephyr/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -408,14 +408,14 @@ config BOOT_VALIDATE_SLOT0_ONCE

config BOOT_PREFER_SWAP_OFFSET
bool "Prefer the newer swap offset algorithm"
default y if SOC_FAMILY_NORDIC_NRF
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@butok butok Apr 23, 2025 •
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Can we make it default for all platforms?
By adding: default y if !$(dt_nodelabel_enabled,scratch_partition)

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It's not been made the default for all platforms due to the sector size requirements, if a device has equal sizes for slot 0 and slot 1 then it will work (but is not ideal) but if it has the swap using move ideal setup of slot 0 being larger than slot 1, it will fail, so has been left as swap using move for default for now

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if a device has equal sizes for slot 0 and slot 1 then it will work (but is not ideal)

Using optimized slot sizes is broken with the latest mcuboot: zephyrproject-rtos/zephyr#88850
It seems, I need to switch to equal slot sizes (at least for NXP) to make it work for all modes, even if it's not optimal.

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That has been fixed efa3039 but has not been pulled into zephyr yet

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That has been fixed efa3039 but has not been pulled into zephyr yet

Great! Thank you.

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having a look at frdm_ke17z it looks like it should work, would be just under 2K for swap status fields so not sure why it throws an error, would suggest enabling debug logs for MCUboot and seeing what is printed, then setting the number of sectors for each slot to the same and seeing what the non-optimal message says

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@butok butok Apr 29, 2025 •
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having a look at frdm_ke17z it looks like it should work, would be just under 2K for swap status fields so not sure why it throws an error, would suggest enabling debug logs for MCUboot and seeing what is printed, then setting the number of sectors for each slot to the same and seeing what the non-optimal message says

For example for frdm_mcxw71, it has Flash total size 1M , 8KB erase and 16B write. Partitioned to:

&flash {
	partitions {
		compatible = "fixed-partitions";
		#address-cells = <1>;
		#size-cells = <1>;
		/* The MCUBoot swap-move algorithm uses the last 2 sectors
		 * of the primary slot0 for swap status and move.
		 */
		boot_partition: partition@0 {
			reg = <0x0 DT_SIZE_K(64)>;
		};
		slot0_partition: partition@10000 {
			reg = <0x10000 (DT_SIZE_K(416) + DT_SIZE_K(16))>;
		};
		slot1_partition: partition@7C000 {
			reg = <0x7C000 DT_SIZE_K(416)>;
		};
		storage_partition: partition@E4000 {
			reg = <0xE4000 DT_SIZE_K(112)>;
		};
	};
};

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BTW: Is see another PR fix is coming "boot: bootutil: Fix max image size computation for swap-move and swap-offset" #2283

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All NXP boards were switched to equal size partitions.
May NXP be switched to SWAP_OFFSET too? Or is it still experimental and better to wait until it becomes the default mode for all?

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I'll cobble together a php script in a bit to check slot0 and slot1 sizes for all boards and see if there's any that are not equal and if so message the maintainers and ask about them because would like to set it as default for all

help
If y, the BOOT_IMAGE_UPGRADE_MODE will default to using "offset" instead of "scratch".
This is a separate bool config option, because Kconfig doesn't allow defaults to be
overridden in choice options. Most devices should be using swap using offset mode.

config BOOT_PREFER_SWAP_MOVE
bool "Prefer the newer swap move algorithm"
default y if SOC_FAMILY_NORDIC_NRF
default y if !$(dt_nodelabel_enabled,scratch_partition)
help
If y, the BOOT_IMAGE_UPGRADE_MODE will default to using
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