soc: stm32n6: Compute FLASH_SIZE when XIP=y

In XIP, we need to know FLASH_SIZE.

Signed-off-by: Erwan Gouriou <[email protected]>

Author: erwango

soc/st/stm32/stm32n6x/Kconfig.defconfig

@@ -10,6 +10,15 @@ rsource "Kconfig.defconfig.stm32n6*"
 DT_STM32_CPU_CLOCK_PATH := $(dt_nodelabel_path,cpusw)
 DT_STM32_CPU_CLOCK_FREQ := $(dt_node_int_prop_int,$(DT_STM32_CPU_CLOCK_PATH),clock-frequency)
 
+DT_CHOSEN_Z_FLASH := zephyr,flash
+DT_CHOSEN_FLASH_NODE := $(dt_chosen_path,$(DT_CHOSEN_Z_FLASH))
+DT_FLASH_HAS_SIZE_PROP := $(dt_node_has_prop,$(DT_CHOSEN_FLASH_NODE),size)
+
+# When XiP in Ext Flash, get FLASH size from size property of XSPI device node
+config FLASH_SIZE
+	default $(dt_node_int_prop_int,$(DT_CHOSEN_FLASH_NODE),size,kb) \
+		if $(DT_FLASH_HAS_SIZE_PROP) && XIP
+
 # For STM32N6, override the value defined in STM32 Kconfig to use CPU clock frequency
 config SYS_CLOCK_HW_CYCLES_PER_SEC
 	default "$(DT_STM32_CPU_CLOCK_FREQ)" if "$(dt_nodelabel_enabled,cpusw)"