OTFDEC internal peripheral

Applicable for

STM32MP21x lines, STM32MP23x lines, STM32MP25x lines

---

1. Article purpose

The purpose of this article is to:

• briefly introduce the OTFDEC peripheral and its main features,
• indicate the peripheral instances assignment at boot time and their assignment at runtime (including whether instances can be allocated to secure contexts),
• list the software frameworks and drivers managing the peripheral,
• explain how to configure the peripheral.

2. Peripheral overview

The OTFDEC peripheral is used to decrypt data on read request. The peripheral is used on top of an OCTOSPI to allow on the fly decryption of associated data from connected mass storage.

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

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

3.1. Boot time assignment

3.1.1. On STM32MP21x lines 

Click on to expand or collapse the legend...

Check boxes illustrate the possible peripheral allocations supported by OpenSTLinux BSP:

• ⬚ means that the peripheral can be assigned to the given boot time context, but this configuration is not supported in OpenSTLinux BSP.
• ☐ means that the peripheral can be assigned to the given boot time context.
• ☑ means that the peripheral is assigned by default to the given boot time context and that the peripheral is mandatory for the OpenSTLinux BSP.
• ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.

The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32 MPU reference manuals.

Domain	Peripheral	Boot time allocation				Comment
		Instance	Cortex-A35 secure (ROM code)	Cortex-A35 secure (TF-A BL2)	Cortex-A35 nonsecure (U-Boot)
Security	OTFDEC	OTFDEC1		⬚	⬚

3.1.2. On STM32MP23x lines 

Click on to expand or collapse the legend...

Check boxes illustrate the possible peripheral allocations supported by OpenSTLinux BSP:

• ⬚ means that the peripheral can be assigned to the given boot time context, but this configuration is not supported in OpenSTLinux BSP.
• ☐ means that the peripheral can be assigned to the given boot time context.
• ☑ means that the peripheral is assigned by default to the given boot time context and that the peripheral is mandatory for the OpenSTLinux BSP.
• ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.

The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32 MPU reference manuals.

Domain	Peripheral	Boot time allocation				Comment
		Instance	Cortex-A35 secure (ROM code)	Cortex-A35 secure (TF-A BL2)	Cortex-A35 nonsecure (U-Boot)
Security	OTFDEC	OTFDEC1		⬚	⬚
		OTFDEC2		⬚	⬚

3.1.3. On STM32MP25x lines 

Click on to expand or collapse the legend...

Check boxes illustrate the possible peripheral allocations supported by OpenSTLinux BSP:

• ⬚ means that the peripheral can be assigned to the given boot time context, but this configuration is not supported in OpenSTLinux BSP.
• ☐ means that the peripheral can be assigned to the given boot time context.
• ☑ means that the peripheral is assigned by default to the given boot time context and that the peripheral is mandatory for the OpenSTLinux BSP.
• ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.

The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32 MPU reference manuals.

Domain	Peripheral	Boot time allocation				Comment
		Instance	Cortex-A35 secure (ROM code)	Cortex-A35 secure (TF-A BL2)	Cortex-A35 nonsecure (U-Boot)
Security	OTFDEC	OTFDEC1		⬚	⬚
		OTFDEC2		⬚	⬚

3.2. Runtime assignment

3.2.1. On STM32MP21x lines 

Click on to expand or collapse the legend...

STM32MP21 internal peripherals

Check boxes illustrate the possible peripheral allocations supported by OpenSTLinux BSP:

• ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in OpenSTLinux BSP.
• ☐ means that the peripheral can be assigned to the given runtime context.
• ☑ means that the peripheral is assigned by default to the given runtime context and that the peripheral is mandatory for the OpenSTLinux BSP.
• ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.

Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32MP21 reference manuals.

Domain	Peripheral	Runtime allocation					Comment
		Instance	Cortex-A35 secure (OP-TEE / TF-A BL31)	Cortex-A35 nonsecure (Linux)	Cortex-M33 secure (TF-M)	Cortex-M33 nonsecure (STM32Cube)
Security	OTFDEC	OTFDEC1	⬚OP-TEE	⬚	⬚	⬚

3.2.2. On STM32MP23x lines 

Click on to expand or collapse the legend...

STM32MP23 internal peripherals

Check boxes illustrate the possible peripheral allocations supported by OpenSTLinux BSP:

• ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in OpenSTLinux BSP.
• ☐ means that the peripheral can be assigned to the given runtime context.
• ☑ means that the peripheral is assigned by default to the given runtime context and that the peripheral is mandatory for the OpenSTLinux BSP.
• ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.

Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32MP23 reference manuals.

Domain	Peripheral	Runtime allocation					Comment
		Instance	Cortex-A35 secure (OP-TEE / TF-A BL31)	Cortex-A35 nonsecure (Linux)	Cortex-M33 secure (TF-M)	Cortex-M33 nonsecure (STM32Cube)
Security	OTFDEC	OTFDEC1	⬚OP-TEE	⬚	⬚	⬚
		OTFDEC2	⬚OP-TEE	⬚	⬚	⬚

3.2.3. On STM32MP25x lines 

Click on to expand or collapse the legend...

STM32MP25 internal peripherals

Check boxes illustrate the possible peripheral allocations supported by OpenSTLinux BSP:

• ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in OpenSTLinux BSP.
• ☐ means that the peripheral can be assigned to the given runtime context.
• ☑ means that the peripheral is assigned by default to the given runtime context and that the peripheral is mandatory for the OpenSTLinux BSP.
• ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.

Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possibilities might be described in STM32MP25 reference manuals.

Domain	Peripheral	Runtime allocation						Comment
		Instance	Cortex-A35 secure (OP-TEE / TF-A BL31)	Cortex-A35 nonsecure (Linux)	Cortex-M33 secure (TF-M)	Cortex-M33 nonsecure (STM32Cube)	Cortex-M0+ (STM32Cube)
Security	OTFDEC	OTFDEC1	⬚OP-TEE	⬚	⬚	⬚
		OTFDEC2	⬚OP-TEE	⬚	⬚	⬚

4. Software frameworks and drivers

Information

The OTFDEC peripheral is currently not supported in OpenSTLinux software.

Board support package

Arm^® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.

Cortex^®

Read only memory

Trusted firmware for Arm^® Cortex^®-A

Boot loader stage 2

Das U-Boot -- the universal boot loader (see U-Boot)

Open portable trusted execution environment

Linux^® is a registered trademark of Linus Torvalds.

Board support package

Arm^® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.

Cortex^®

Read only memory

Trusted firmware for Arm^® Cortex^®-A

Boot loader stage 2

Das U-Boot -- the universal boot loader (see U-Boot)

Open portable trusted execution environment

Linux^® is a registered trademark of Linus Torvalds.