GIC internal peripheral

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1. Article purpose[edit source]

The purpose of this article is to

briefly introduce the GIC peripheral (generic interrupt controller) and its main features
indicate the level of security supported by this hardware block
explain how each instance can be allocated to the three runtime contexts and linked to the corresponding software components
explain, when needed, how to configure the GIC peripheral.

2. Peripheral overview[edit source]

The GIC peripheral is the Arm^® Cortex^®-A7 interrupt controller. It is consequently not accessible from the Arm^® Cortex^®-M4 core.

2.1. Features[edit source]

Refer to STM32MP15 reference manuals for the complete list of features, and to the software components, introduced below, to know which features are really implemented.

2.2. Security support[edit source]

The GIC is a secure peripheral (under ETZPC control).

3. Peripheral usage and associated software[edit source]

3.1. Boot time[edit source]

The GIC is configured by the FSBL (see Boot chain overview), mainly to define the routing of each interrupt to the secure or non-secure context at runtime.

3.2. Runtime[edit source]

3.2.1. Overview[edit source]

The GIC can be allocated:

to the Arm^® Cortex^®-A7 secure core to be used under OP-TEE with the GIC OP-TEE driver (or TF-A secure monitor if the OP-TEE is not present)
or to the Arm^® Cortex^®-A7 non-secure core to be used under Linux^® with the interrupts framework

3.2.2. Software frameworks[edit source]

Domain	Peripheral	Software components			Comment
Domain	Peripheral	OP-TEE	Linux	STM32Cube	Comment
Core/Interrupts	GIC	OP-TEE GIC driver	Linux interrupt framework

3.2.3. Peripheral configuration[edit source]

The configuration is applied by the firmware running in the context to which the peripheral is assigned. The configuration by itself can be performed via the STM32CubeMX tool for all internal peripherals. It can then be manually completed (especially for external peripherals) according to the information given in the corresponding software framework article.

3.2.4. Peripheral assignment[edit source]

Internal peripherals

Check boxes illustrate the possible peripheral allocations supported by STM32 MPU Embedded Software:

☐ means that the peripheral can be assigned (☑) to the given runtime context.
✓ is used for system peripherals that cannot be unchecked because they are statically connected in the device.

Refer to How to assign an internal peripheral to a runtime context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possiblities might be described in STM32MP15 reference manuals.

Domain	Peripheral	Runtime allocation				Comment
Domain	Peripheral	Instance	Cortex-A7 secure (OP-TEE)	Cortex-A7 non-secure (Linux)	Cortex-M4 (STM32Cube)	Comment
Core/Interrupts	GIC	GIC	✓	✓