USB2PHY internal peripheral

Applicable for

STM32MP23x lines  STM32MP25x lines

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1. Article purpose

The purpose of this article is to:

• briefly introduce the USB2PHY 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 USB2PHY peripheral is a block that contains a USB high-speed UTMI+ PHY. It makes the interface between:

• the internal USB controllers (USBH and USB3DR),
• the external USB physical lines (DP, DM).

The USB2PHY peripheral is connected to the following controllers:

SoC	USB2PHY1	USB2PHY2
STM32MP21x lines	USBH	OTG
STM32MP23x lines		USB3DR for USB2.0 speeds.
STM32MP25x lines

SoC	USB2PHY Block diagram
On STM32MP21x lines
On STM32MP23x lines
On STM32MP25x lines

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 

One USB2PHY instance, that is, USB2PHY2, is a boot device that support Flash programming with STM32CubeProgrammer.

The USB2PHY2 instance is used by ROM code, FSBL and SSBL when using OTG in Device mode (DFU).

Click on to expand or collapse the legend...

• ☐ 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 Yocto-based OpenSTLinux Embedded Software.
• ⬚ means that the peripheral can be assigned to the given boot time context, but this configuration is not supported in Yocto-based OpenSTLinux Embedded Software.
• ✓ 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)
High speed interface	USB2PHY	USB2PHY1	⬚	⬚	☐	USB2PHY1 can be used in U-boot by USBH with command line tools.
		USB2PHY2	☐	☐	☐	USB2PHY2 can be used by ROM code, FSBL and SSBL in DFU mode to support serial boot. It can be used also in U-boot by OTG with command line tools.

3.1.2. On STM32MP23x lines  and STM32MP25x lines 

One USB2PHY instance, that is, USB2PHY2, is a boot device that support Flash programming with STM32CubeProgrammer.

The USB2PHY2 instance is used by ROM code, FSBL and SSBL when using USB3DR in Device mode (DFU).

Click on to expand or collapse the legend...

• ☐ 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 Yocto-based OpenSTLinux Embedded Software.
• ⬚ means that the peripheral can be assigned to the given boot time context, but this configuration is not supported in Yocto-based OpenSTLinux Embedded Software.
• ✓ 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)
High speed interface	USB2PHY	USB2PHY1	⬚	⬚	☐	USB2PHY1 can be used in U-boot by USBH with command line tools.
		USB2PHY2	☐	☐	☐	USB2PHY2 can be used by ROM code, FSBL and SSBL in DFU mode to support serial boot. It can be used also in U-boot by USB3DR with command line tools.

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 Yocto-based OpenSTLinux Embedded Software:

• ☐ 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 Yocto-based OpenSTLinux Embedded Software.
• ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in Yocto-based OpenSTLinux Embedded Software.
• ✓ 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)
High speed interface	USB2PHY	USB2PHY1	⬚OP-TEE ⬚TF-A BL31	☐	⬚	☐	Allocation inherited from USBH
		USB2PHY2	☐OP-TEE ☐TF-A BL31	☐	☐	☐	Allocation inherited from OTG

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 Yocto-based OpenSTLinux Embedded Software:

• ☐ 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 Yocto-based OpenSTLinux Embedded Software.
• ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in Yocto-based OpenSTLinux Embedded Software.
• ✓ 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)
High speed interface	USB2PHY	USB2PHY1	⬚OP-TEE ⬚TF-A BL31	☐	⬚	☐	Allocation inherited from USBH
		USB2PHY2	☐OP-TEE ☐TF-A BL31	☐	☐	☐	Allocation inherited from USB3DR

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 Yocto-based OpenSTLinux Embedded Software:

• ☐ 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 Yocto-based OpenSTLinux Embedded Software.
• ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in Yocto-based OpenSTLinux Embedded Software.
• ✓ 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)
High speed interface	USB2PHY	USB2PHY1	⬚OP-TEE ⬚TF-A BL31	☐	⬚	☐		Allocation inherited from USBH
		USB2PHY2	☐OP-TEE ☐TF-A BL31	☐	☐	☐		Allocation inherited from USB3DR

4. Software frameworks and drivers

Below are listed the software frameworks and drivers managing the USB2PHY peripheral for the embedded software components listed in the above tables.

• Linux^®: PHY framework, USB2PHY driver (drivers/phy/st/phy-stm32-usb2phy.c )
• U-Boot: PHY uclass (drivers/phy/phy-uclass.c ) and driver (drivers/phy/phy-stm32-usb2phy.c )

5. How to assign and configure the peripheral

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

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

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

For U-boot and Linux kernel configuration, please refer to USB2PHY device tree configuration.

USB 2.0 Transceiver Macrocell Interface

Physical layer protocol

Board support package

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

Cortex^®

Flash memory shortened to gain space in titles, tables and block diagrams

Device firmware upgrade

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.

Hardware abstraction layer

USB 2.0 Transceiver Macrocell Interface

Physical layer protocol

Board support package

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

Cortex^®

Flash memory shortened to gain space in titles, tables and block diagrams

Device firmware upgrade

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.

Hardware abstraction layer

Flash memories combine high density and cost effectiveness of EPROMs with the electrical erasability of EEPROMs. For this reason, the Flash memory market is one of the most exciting areas of the semiconductor industry today and new applications requiring in system reprogramming, such as cellular telephones, automotive engine management systems, hard disk drives, PC BIOS software for Plug & Play, digital TV, set top boxes, fax and other modems, PC cards and multimedia CD-ROMs, offer the prospect of very high volume demand.