Using OSPI from non-secure with Trusted Firmware on STM32u585

[taunboel]

Hello, I've been trying to build an application with Trusted Firmware and using Zephyr RTOS for the non-secure application i'm using b_u585i_iot02a board. After i build my application, the OSPI is not working anymore from my non-secure application. I can see from AN5247 and RM0456 that the default security state of the OSPI banks when building with trusted firmware is secure, which then makes sense. So my question is: Is it true that the OSPI is non acccessible from non-secure application when building with trusted firmware pr. default?

And if yes, how can i disable this so i'm able to use it from my non-secure application as before?

[CMYL]

Hello,

My understanding of RM0456 Table 28. MPCWM resource assignment ans "Figure 15. GTZC in Armv8-M subsystem block diagram" external memory can be configured as sec or nsec using GTZC/MPCWMx.

For setting OCTOSPIx as secure or non-secure refer to 5.6.4 GTZC1 TZSC secure configuration register 3 (GTZC1_TZSC_SECCFGR3)

Best Regards,

Younes

[taunboel]

Hey again @Younes LAHBIB​ ,

i now have had some time to dig on this subject and for what i can see when i read out the value of the GTZC1_TZSC_SECCFGR3 and the GTZC1_TZSC_PRIVCFGR3 register (both from secure and non secure) i get 0's on bits corresponding to the security access/priviledge level on the OCTOSPI, which means that the access/privilidge on the OCTOSPI should be non-secure and unprivileged. Which means, as far as I understand, that i should be able to use the OCTOSPI as normal from my non-secure Zephyr Application. I'm still getting an write enable failed error from the non-secure flash driver, which is working, when i'm building and flashing without TF-M/TZEN enabled. Is there something that i'm missing or misunderstanding?

Best Regards,

Tobias

[CMYL]

Hey again,

We are still analyzing this issue.

Can you dump the registers when the issue happened ?

We asked if you see any security violation like ILA or hard fault when write enabled failed ?

Best regards,

Younes

[taunboel]

Hey again @Younes LAHBIB​ thanks for getting back to me regarding this issue.

I have attached a dump of the GTZC1_TZC, OCTOSPI2, GTZC1_TZIC registers around when the Error inside the driver (stm32u5xx_hal_ospi.c) in the function HAL_OSPI_AutoPolling is happening. I have just dumped the registers in my gdb debug session, so sorry if the format isn't so pretty, but it's readable.

​

I don't see any secure violation like hard fault or anything in the TZIC registers, which is also wondering me a bit.

Let me now if it's not enough info or i can provide you with anything else.

Best Regards,

Tobias