Introduction

Introduction to DM

Traditional Texas Instruments SoCs have implemented system control functions such as power management within operating systems on each of the processing units (ARM/DSP). However, such a traditional approach has had tremendous challenges to ensure system stability. Few of the challenges faced include:

Complex interactions between Operating Systems on heterogeneous SoCs for generic features.
Lack of centralized knowledge of system state.
Consistency in SoC feature entitlement in all OSes for the SoC for complex SoC features and system quirks.

Device Management (DM) and TI Foundational Security Software(TIFS) attempt to resolve these issues by being a consistent component of Keystone 3 SoC architecture performing the role of a centralized SoC power, security and device management controller.

In effect, this is a microcontroller and runs a safety and security certified firmware that provides services to the rest of the OSes/Software running on various other processors on the SoC.

DM Power Management

DM controls the power management of the device, hence is responsible for bringing the device out of reset, enforce clock and reset rules. DM power management functions are critical to bring device to low power modes, for example DeepSleep, and sense wake-up events to bring device back online to active state.

TIFS Security Management

The TIFS firmware manages SoC central security resources. The security subsystem provides APIs to other software entities to avail these features in a controlled and secure way. The security management firmware is subdivided into modules listed below:

Firewall management
ISC management
Boot authentication
SA2UL context management (for encryption and authentication)
Crypto APIs (to access common SA2UL functions such as PKA, RNG)
Secure keys management
Secure debug

DM Resource Management

The DM firmware Resource Management (RM) (sub) system manages SoC shared resources. RM manages access and configuration of shared resources amongst SoC processing entities. RM provides a set of interfaces over which SoC processing entities can allocate and free access to shared resources.

The resource management firmware is subdivided into modules listed below:

Core database
IRQ management
Ring accelerator management
UDMA-P management
PSI-L management
Non-secure proxy management

Communication with DM

DM is a "black box" with respect to the other processing entities (ARM/DSP) on the SoC. Communication with DM occurs over a messaging protocol called the Texas Instruments System Control Interface (TI-SCI). TI-SCI is a predefined request-response protocol that provides access to the various services provided by DM.

The actual messaging hardware block varies depending on SoC, but typical examples include "Proxy over message manager" and "Secure Proxy over Ring Accellerator". These communication mechanisms are standardized and secured by DM firmware prior to operation.

The request/response format is described overall as in Figure 2 . The message type describes the service to be performed and is operated on depending on few attributes including privileges allowed and operational state of the SoC.

Type	Byte Index	Data Type	Header
TISCI Header	[0:1]	U16	Message_type
	[2]	uint8_t	Host
	[3]	uint8_t	Sequence_id
	[4:7]	U32	Flags
Payload	Depends on type of message		Payload Fields