Hi all,
I am trying to align TrustZone initialisation procedure between TF-M and CMSIS.
In CMSIS the approach from the early v8-M days is to have a "partition.h" file providing "TZ_SAU_Setup()" function. This function is called during low level "SystemInit()" which runs as part of the pre-main (called from ResetHandler and before running C lib init).
In contrast TF-M calls "tfm_spm_hal_init_isolation_hw()" (which is similar to "TZ_SAU_Setup()" plus PPC/MPC configuration) during "tfm_core_init()" (which runs in secure "main()").
The advantage of "TZ_SAU_Setup()" is that this function is available by standard for all TrustZone devices. The shortcoming is it doesn't cover MPC/PPC configuration, yet. Ideally we can enhance CMSIS standard to offer a "TrustZone_Setup()" function (the name is still to be defined) that does all this. That would simplify the TF-M HAL to just one single function call that should be provided by each TrustZone-Device low level init code.
The final question is: When does this function need to be called? Are you aware of any reason why we should not configure the "system isolation" already during low level init (pre-main)? This could simplify TF-M code even more. In TF-M we could simply rely on a properly configured TrustZone isolation before running any TF-M code.
Cheers,
Jonatan Antoni Senior Engineering Manager - CMSIS [Germany on Google Android 8.0] [United Kingdom on Google Android 8.0]
Arm Germany GmbH Phone: +49 (0)89 262 029 618 | Fax: +49 (0)89 456 040-19 Email: jonatan.antoni@arm.commailto:jonatan.antoni@arm.com | Visit: www.keil.comhttp://www.keil.com | Address: Bretonischer Ring 16, 85630 Grasbrunn, Germany Sitz der Gesellschaft: Grasbrunn | Handelsregister: München (HRB 175362) | USt-IdNr.: DE 187925309 Geschäftsführer: Joachim Krech, Reinhard Keil
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