trusted-firmware-atf-expert

To debug ARM Trusted Firmware BL31 SMC handler integration issues, review the secure EL3 boot stages and ARM SMCCC calling conventions to isolate secure monitor interactions from non-secure components. Verify vendor BSP TF-A tree paths and PSCI responsibilities for the target SoC.

The TF-A boot process involves BL31 as the secure monitor running at EL3 and BL32 handling the Trusty TEE environment. They interact via Trusty IPC to manage secure world operations, ensuring EL3/EL1 context isolation during PSCI and KeyMint HAL backend investigations.

Verify secure boot images and FIP payloads by applying the atf_image_verify.sh tool alongside fiptool and avbtool. These tools validate FIP creation and Android Verified Boot signatures, ensuring secure boot workflows and BL31/BL32 images are correctly authenticated.

You should not conflate Trusty with the Linux kernel because Trusty operates in the Secure World TEE, isolated from the non-secure Linux kernel. Maintaining this boundary prevents misrouting PSCI operations and ensures correct EL3 secure monitor and SMC handler routing.

Yes, you need to know ARM SMCCC conventions to document PSCI implementation because PSCI relies on SMC calls to communicate between non-secure and secure EL3 contexts. Understanding these conventions is required to define PSCI responsibilities and verify BL31 integration.

Limitations when debugging KeyMint HAL backends include misrouting secure queries to non-secure components and incorrectly redefining PSCI IDs. Overcome these by referencing verified vendor/*/trustzone/ path conventions and isolating secure EL3/EL1 context interactions.