Sample - how to use EXTMEM (Flash over OSPI) on the STM32U5G9J-DK2?

[fusetim]

Hello there, I'm quite new to Zephyr and I'm working on the STM32U5G9J-DK2 devkit to develop an application.
But at some point, I filled the (S)RAM present on the board, and I would like to make good use of the external flash (128MB) present on the board.

According to the STM32 specs, I should be able t813fd267162a8f917bb6ec90c1d0dc91ae9a7b68o use it directly through the memory-mapped interface (RW), but unfortunately, writing has no effect.

So I'm wondering what are the actual step to enable the external flash and use it with Zephyr, and especially if an example exists somewhere for this board or a similar STM32 board.
Unfortunately, the commit introducing the ext_memory for this board (813fd26) does not mention anything in particular.

I'm open to suggestions and other ideas that would point me in the right direction, thank you all.

[fusetim]

Might be related:

• OSPI PSRAM support for B-U585I-IOT02A #70844 (reply in thread)
• STM32 ospi support for Dual Hyperram/Flash #97138

[FRASTM]

Hello @fusetim

The Commit 813fd26 is the first step.
Then few tests could complete the support of that external flash.
samples/drivers/jesd216 to validate the most basic access
then samples/drivers/spi_flash to validate Rd/Wr to the external flash in indirect mode and MemMapped mode if CONFIG_STM32_MEMMAP is set (it can read but not write)