Introduction

Traditional Texas Instruments SoCs implement system control functions such as power management on each of the processing units (ARM/DSP etc). However, the traditional approach had tremendous challenges to ensure system stability. A few of the challenges include:

• Complex interactions between Operating Systems on heterogeneous SoCs for generic features.
• Lack of centralized knowledge of system state.
• Complex implementation challenges with regards to implementation of workarounds for system quirks.
• Equivalent system capability entitlement on all variations of operation conditions.

Keystone 3 (K3) devices introduces the concept of a centralized Power, Resource and Security Management to allow mitigating the challenges of the traditional approach to system control.

System Firmware is a collective term used to describe the TI Foundational Security (TIFS) and Resource Management (RM)/ Power Management (PM) services.

System Firmware executes on the Security Manager and Device Manager Core. On K3 devices, the DMSC subsystem is the Security Manager Core in the SoC. The Device Manager core can be on the DMSC itself or the MCU R5F. The choice of whether this runs on the DMSC or the MCU R5F is based on the kind of applications the device is targeting. If the device is targetting applications, where there is a need for a dedicated Hardware Security Module (HSM), the Device manager core is independent of the DMSC (which is exclusively kept for Security functions). For devices which do not have need for a dedicated security island or HSM, the device manager runs on the DMSC.

The following table highlights the variations of where the RM and PM execute versus the TIFS on the different K3 family of devices.

Table 1 TI Foundational Security Software and RM/PM SCI Server Mapping

Device	TI Foundation Security	3rd Party HSM/SHE stack	RM/PM SCI Server
AM65x/ DRA80x, AM64x	DMSC (M3 based)	NA	DMSC (M3 based)
DRA82X, TDA4X	DMSC (M3 based)	DMSC (M3 based)	Library on MCU R5*
TDA4VLX	SMS (M4 based)	SMS (M4 based)	Library on MCU R5*
AM62X, AM62Ax, AM62Px	SMS (M4 based)	SMS (M4 based)	Library on DM R5*

Note, the TI provided software does not allow for a given SoC to support both HSM and non HSM applications. To know the mapping refer TI Foundational Security Software and RM/PM SCI Server Mapping.

The purpose of this document is to define the software interface for the System Firmware. The split up of the responsibilities are:

• TIFS:

  • Responsible for Centralized Foundational Security Management. These include functions like authenticated boot, JTAG unlock etc.
  • Behaves like a forwarding agent for Resource Management and Power Management requests made by Secure hosts (other CPUs) in the SoC.
  • Behaves as a forwarding agent for Resource Management and Power Management responses from the device manager to the Secure Hosts.
  • Firewall Management for resources requested by both secure and non-secure hosts.

• Device Manager (DMSC M3 or MCU R5F based on the device)

  • Responsible for servicing resource management and power management messages from secure and non-secure hosts.
  • Reponsible for forwarding non-secure host requests to set the processor boot control or firewall configuration for safety applications to the DMSC.
  • Responsible for forwaring response recieved from the DMSC to non-secure hosts for the above forwarded messages.

Centralized Device Management

In the Power management domain, the centralized power management takes into account that every device has:

• Different power and clock domains.
• Derivatives have slight differences in the clocking architecture based on combination of modules.

It provides an OS agnostic interface for power management allowing peripherals and clocks to be handled by multiple processors running different OSes (Linux, RTOS, etc.). The centralized power management entity aims to provide the same control for power and clock setting across all OSes.

Centralized Resource management is driven by the centralized DMA architecture. Key components of the centralized resource management include:

• Navigator Subsystem: Collection of Data movement components
• UDMA (Unified DMA), PKTDMA, BCDMA: DMA engine for standard parallel DMA (CBA) or PSI/stream based IP.
• RA (Ring Accelerator): Queue management providing abstract SW view to HW DMA queues
• Proxy: Allows efficient access to RA queues, also enables address containment/virtualization (access RA via separate MMU page / regions)
• Interrupt & events handling: Interrupt aggregators and Interrupt routers

Centralized Foundational Security Management

The DMSC M3 subsystem in the K3 family of devices is responsible to run the software stack for the device foundational security management. This software entity is responsible for:

• Foundational device security in DMSC

  • Secure boot with secure keys/root-of-trust, Security configuration and Debug unlock
  • RSA or ECC Root Keys, AES symmetric key
  • Utilizes PKA, SHA2 and AES Crypto accelerators
  • Basic security functionality to extend root of trust (optional)
  • Authenticated Key ring to extend root-of-trust keys
  • SYSFW and Bootloader Rollback protection via eFuse
  • Device Unique Key / Key Derivation to support 3P stacks

The centralized power, resource and security management entity is henceforth refered to as System Control Entity and System Firmware interchangeably. Any software and hardware entity which communicates with the System Control Entity is refered to as “Host”. The block diagram of the System Controller Entity or System firmware is as below:

Fig. 1 System Controller Entity interacting with Other Hosts

Architecture Change between SDK 7.0 and SDK 7.1

The SDK 7.1 (v2020.08 of System Firmware) firmware is not compatible with SDK 7.0. (v2020.04 of the System Firmware) and earlier releases in terms of location of the binaries. Note the TISCI interface is the same as what is available on earlier releases.

The following figure describes the typical software stack and highlights the difference in the location of execution of centralized services from System Firmware.

Fig. 2 DMSC Firmware Change | TDA4VM, DRA829, DRA821

Purpose of DMSC firmware change

• Secure HSM functions can run on a DMSC Security Island
• Free a main domain R5F for general customer use.
• Enables MCU Only mode with HSM functions on DMSC
• Lockstep Safety R5F runs safety critical PM & RM functions.

The Memory / CPU requirement is minimal (< 150 KB, < 10 MHz) so having the RM and PM execute on the MCU R5f has minimal impact to user applications.

The SW impact summary for the end users is as given below. Kindly note since the API interface remains the same, the rest of the documentation for System Firmware is the same between SDK 7.1 and 7.0. Refer to the SDK documentation to know more about the changes required for integration of the SCISERVER and RM/PM on the MCU R5F.

Fig. 3 SW Impact for end-users between SDK 7.0 and SDK 7.1

Further Reading

• In Chapter 2: TISCI Message Documentation, we describe how one can communicate with the system control entity and the various messages that can be used.
• In Chapter 3: Board Configuration, we desribe the format and content of the boardcfg messages that does onetime configuration of System Firmware.
• In Chapter 4: Interpreting Trace Data, we define trace data format.
• In Chapter 5: SoC Family Specific Documentation, we provide information specific to each SOC that is required using the TISCI messages described in Chapter 2: TISCI Message Documentation.
• In Chapter 6: Topic User Guides, we provide user guides for the more complex scenarios.

Glossary

The following list defines the different acronyms and terms used in the rest of the document:

• TIFS (Texas Instruments Foundational Security): Foundational security software provided from TI.
• TISCI (Texas Instruments System Controller Interface) : API interface to TIFS, RM/PM services.
• DM (Device Manager) : Collective term used to refer to the Resource Management and Power Management Software.
• RM (Resource Management): Term used to refer to the Resource Management Software.
• PM (Power Management): Term used to refer to the Power Management Software.
• SYSFW (System Firmware): Collective term used to refer to the TIFS and RM/PM Software.