DSI internal peripheral





1 Article purpose[edit]

The purpose of this article is to:

  • briefly introduce the DSI peripheral 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 necessary, how to configure the DSI peripheral.

2 Peripheral overview[edit]

The DSI peripheral implements all the protocol functions defined in the MIPI® Display Serial Interface (MIPI® DSI) specification. It provides an interface to communicate with a DSI-compliant display. The MIPI® DSI is part of a group of communication protocols defined by the MIPI® Alliance [1].

2.1 Features[edit]

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

2.2 Security support[edit]

The DSI is a non-secure peripheral.

3 Peripheral usage and associated software[edit]

3.1 Boot time[edit]

The DSI is used at boot time for displaying a splash screen thanks to the U-Boot framework [2].

3.2 Runtime[edit]

3.2.1 Overview[edit]

The DSI internal peripheral is allocated to the Arm® Cortex®-A7 non-secure core to be controlled in Linux® by the Linux DRM/KMS framework.

Chapter Peripheral assignment describes which peripheral instance can be assigned to which context.

3.2.2 Software frameworks[edit]

Domain Peripheral Software frameworks Comment
Cortex-A7
secure
(OP-TEE)
Cortex-A7
non-secure
(Linux)
Cortex-M4

(STM32Cube)
Visual DSI DRM/KMS framework

3.2.3 Peripheral configuration[edit]

The configuration is applied by the firmware running in the context to which the peripheral is assigned. The configuration can be done alone via the STM32CubeMX tool for all internal peripherals, and then manually completed (particularly for external peripherals), according to the information given in the corresponding software framework article or for Linux® in the DSI device tree configuration article.

3.2.4 Peripheral assignment[edit]

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
Instance Cortex-A7
secure
(OP-TEE)
Cortex-A7
non-secure
(Linux)
Cortex-M4

(STM32Cube)
Visual DSI DSI

4 How to go further[edit]

Refer to the STM32 DSI application note (AN4860) [3] for a detailed description of the DSI peripheral and applicable use-cases.

Even if this application note is related to STM32 microcontrollers, it also applies to STM32 MPUs.

5 References[edit]

Display Serial Interface (MIPI® Alliance standard)

Mobile Industry Processor Interface, open membership organization that includes leading companies in the mobile industry that share the objective of defining and promoting open specifications for interfaces inside mobile terminals, see MIPI® Alliance standard web site https://www.mipi.org

Open Portable Trusted Execution Environment

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