Microboot 2

The next stage of the boot sequence is Microboot 2 (MB2). The sequence is as follows:

Under MB2 (yellow) - seq. is as follows:

• 1. init MB2

• 2. init pt and storage device

• 4. Load DVFS tables

• 3. Lock oem security settings

• 5. trigger pscbl1-exit and start bpmp-fw (started by pscbl1)

• 4. Load and unhalt fsi-fw

• 5. Wait for bpmp-fw to consume DVFS tables

• 6. load and auth/validate em firmwares

• 7. unhalt oem fw

• 8. load and uath ATF and foundation image

• 9. Prepare ATF params

• 10. start ATF params.

Under pscbl1 (blue), wait for pscbl1 exit step is not required. That’s the step executed by mb2 after triggering pscbl1 exit.

In step 2, MB2 has ability to utilize QSPI or UFS as the boot device for the remaining boot payloads. This is determined through the NV Partition Table settings.

MB2 loads and validates additional OEM firmware that configures the SoC to run more complex software components.

Like MB1, MB2 also prepares more SC7 context, which includes saving MB2-BCT data, AUXP-FW data, etc.

The additional firmware components are as follows:

Firmware Component	Description
Audio Processor Engine Firmware (APE-FW)	Provides the facilities for audio processing.
ATF/TOS image	Provide EL3 and Secure EL1 support.
Functional Safety Island Firmware (FSI-FW)	Provide the monitoring and reporting of functional safety errors.
Realtime Engine Firmware (RCE-FW)	Provides the realtime camera processing engine
Display Control Engine Firmware (DCE-FW)	Provides the realtime display processing engine.
Foundation image	Provides the Hypervisor stack and servers.