@erwango and @etienne-lms do you mind having a look at this?

Quality Gate passed

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0.0% Coverage on New Code
17.2% Duplication on New Code

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I switched to the mcuboot bootloader and digged into sysbuild stuff. I tried to follow #88579 where things are done for the h5, but the h7 family is somehow more complicated (or my understanding of h5 details are wrong).

Commit soc: st: stm32: h7rsx: Disable core power and VOS config for XiP (39d3878)

The chain-loaded application must not switch to LL_PWR_REGU_VOLTAGE_SCALE1, because the bootloader most likely setup a fast core clock.

Commit boards: arm: st: nucleo_h7s3l8: Add *-block-size properties to xspi2 (d0aeb47)

• Build output of mcuboot complained about not defined write-block-size and erase-block-size. Added those properties in the same way as it's done in the other h7rs eval board.
• One must be careful to set zephyr,flash-controller = &ext_flash_ctrl to still have CONFIG_STM32_APP_IN_EXT_FLASH defined, as the first condition is not met anymore in soc/st/stm32/Kconfig.defconfig: config STM32_APP_IN_EXT_FLASH default $(DT_FLASH_PARENT_IS_XSPI) || $(DT_FLASH_CTRL_IS_XSPI_NOR)

Commit drivers: flash: stm32_xspi: Remove hard-coded XSPI2 dependency (6cbf0b8)

• flash_stm32_xspi.c had hardcoded calls to LL_PWR_EnableXSPIM2() and LL_SBS_EnableXSPI2SpeedOptim()
• added a check of the used XSPIx peripheral before calling the corresponding function of XSPI1/2

Commit dts: arm: st: h7rs: Enable HSI internal clock (70eb6e5)

• I wondered why old_hclk_freq in stm32_clock_control_init(const struct device *dev) was always calculated to 0 and activated hsi clock note in the soc's dt to fix it
• HSI on is the devices reset default value anyway, but the STM32_HSI_FREQ define is set to 0 when not enabled.

Commit drivers: clk: stm32_ll_h7: Add stm32_clock_control_get_status function (025fd7e)

• added stm32_clock_control_get_status() in h7 clock driver similar to the h5 one
• I thought this is needed by flash_stm32_xspi_init() with the call to clock_control_get_status(). But flash_stm32_xspi_init() does not seem to be called a second time when starting the chain-loaded app. Any explanations?

Commit drivers: clock: stm32_ll_h7: Disable clock configuration for XiP (90bc050)

Ok, now it gets ugly. I don't like this long list of #ifdefs and #defines, but I didn't find a short way implement this behaviour:

• The chain-loaded application must not
  • modify the clock path to the Q/O/X-SPI peripheral
  • modify the HCLK when XSPI clock could be higher (XSPI axi vs. kernel clock constraint in h7rs)
  • switch the Q/O/X-SPI peripheral clock (by switching SYSCLOCK from PLL1 to HSI during re-config, when XSPI is clocked from HCLK) - not sure about this constraint, but at least for XSPI I can't image that's a good idea.
• The chain-loaded application should be able to
  • re-configure all PLLs not used in the clock path to the Q/O/X-SPI peripheral
  • re-configure all PLL outputs not used in the clock path to the Q/O/X-SPI peripheral
• That way a later change to the board's clock config can be done without updating mcuboot when not interfering with XiP function.

With these changes I am able to run the with_mcuboot example at a SYSCLK of 600MHz and the XSPI at 200MHz from PLL2S. Will hardfault without.
Changes to the nucleo_h7s3l8 board dt:

&pll {
	div-m = <2>;
	mul-n = <50>;
	div-p = <1>;
	div-q = <2>;
	div-r = <2>;
	div-s = <2>;
	div-t = <2>;
	clocks = <&clk_hse>;
	status = "okay";
};

/* PLL2 for clocking the xspi peripheral */
&pll2 {
	div-m = <12>;
	mul-n = <200>;
	div-p = <2>;
	div-q = <2>;
	div-r = <2>;
	div-s = <2>;
	div-t = <2>;
	clocks = <&clk_hse>;
	status = "okay";
};

&rcc {
	clocks = <&pll>;
	clock-frequency = <DT_FREQ_M(600)>;
	dcpre = <1>;
	hpre = <2>;	// BMPRE
	ppre1 = <2>;
	ppre2 = <2>;
	ppre4 = <2>;
	ppre5 = <2>;
	status = "okay";
};

The xspi2 node's clock setting must be changed to:

clocks =  <&rcc STM32_CLOCK(AHB5, 12)>,
		  <&rcc STM32_SRC_PLL2_S XSPI2_SEL(1)>, //0=HCLK5, 1=PLL2S, 2=PLL2T
		  <&rcc STM32_CLOCK(AHB5, 14)>; //only needed when XSPIM register access needed
clock-names = "xspix", "xspi_ker", "xspi_mgr";