Last edited 2 weeks ago

RNG internal peripheral


1. Article purpose[edit | edit source]

The purpose of this article is to:

  • Briefly introduce the RNG peripheral and its main features.
  • List the software frameworks and drivers managing the peripheral.
  • Explain how to configure the peripheral.

2. Peripheral overview[edit | edit source]

The RNG peripheral is used to provide 32-bit random numbers.

Refer to the STM32 MPU reference manuals for the complete list of features, and to the software frameworks and drivers, introduced below, to see which features are implemented.

3. Peripheral usage[edit | edit source]

This chapter is applicable in the scope of the OpenSTLinux BSP running on the Arm® Cortex®-A processor, and the STM32CubeMPU Package running on the Arm® Cortex®-M processor.

Refer to the wiki article Hardware random overview to learn more on the possible usages of this peripheral.

3.1. Boot time assignment[edit | edit source]

3.1.1. On STM32MP13x lines More info.png[edit | edit source]

Click on How to.png to expand or collapse the legend...

Domain Peripheral Boot time allocation Comment How to.png
Instance Cortex-A7
secure
(ROM code)
Cortex-A7
secure
(TF-A BL2)
Cortex-A7
non-secure
(U-Boot)
Security RNG RNG Required for DPA peripheral protection

3.1.2. On STM32MP15x lines More info.png[edit | edit source]

Click on How to.png to expand or collapse the legend...

Domain Peripheral Boot time allocation Comment How to.png
Instance Cortex-A7
secure
(ROM code)
Cortex-A7
secure
(TF-A BL2)
Cortex-A7
non-secure
(U-Boot)
Security RNG RNG1

3.1.3. On STM32MP2 series[edit | edit source]

Click on How to.png to expand or collapse the legend...

Domain Peripheral Boot time allocation Comment How to.png
Instance Cortex-A35
secure
(ROM code)
Cortex-A35
secure
(TF-A BL2)
Cortex-A35
non-secure
(U-Boot)
Security RNG RNG

3.2. Runtime assignment[edit | edit source]

If the Arm® Cortex®-A processor hardware RNG peripheral is assigned to OP-TEE, then the Linux kernel can request random numbers through the hardware random framework, which is interfaced with the OP-TEE RNG Linux driver .

If the Arm® Cortex®-A processor hardware RNG peripheral is assigned to the Linux kernel, then the Linux kernel can access it through the hardware random framework, which is interfaced with the Linux RNG driver .

3.2.1. On STM32MP13x lines More info.png[edit | edit source]

Click on How to.png to expand or collapse the legend...

Domain Peripheral Runtime allocation Comment How to.png
Instance Cortex-A7
secure
(OP-TEE)
Cortex-A7
non-secure
(Linux)
Security RNG RNG Assignment (single choice)

3.2.2. On STM32MP15x lines More info.png[edit | edit source]

Click on How to.png to expand or collapse the legend...

Domain Peripheral Runtime allocation Comment How to.png
Instance Cortex-A7
secure
(OP-TEE)
Cortex-A7
non-secure
(Linux)
Cortex-M4

(STM32Cube)
Security RNG RNG1 Assignment (single choice)
RNG2

3.2.3. On STM32MP25x lines More info.png[edit | edit source]

Click on How to.png to expand or collapse the legend...

Domain Peripheral Runtime allocation Comment How to.png
Instance Cortex-A35
secure
(OP-TEE /
TF-A BL31)
Cortex-A35
non-secure
(Linux)
Cortex-M33
secure
(TF-M)
Cortex-M33
non-secure
(STM32Cube)
Cortex-M0+
Warning.png
(STM32Cube)
Security RNG RNG OP-TEE

4. Software frameworks and drivers[edit | edit source]

Below are listed the software frameworks and drivers managing the RNG peripheral for the embedded software components listed in the above tables.

5. How to assign and configure the peripheral[edit | edit source]

The peripheral assignment can be done via the STM32CubeMX graphical tool (and manually completed if needed).
This tool also helps to configure the peripheral:

  • Partial device trees (pin control and clock tree) generation for the OpenSTLinux software components.
  • HAL initialization code generation for the STM32CubeMPU Package.

The configuration is applied by the firmware running in the context in which the peripheral is assigned.

This configuration is done in OP-TEE through the device tree.
For more information, refer to the wiki article RNG device tree configuration.

6. References[edit | edit source]