USB2PHY internal peripheral

Applicable for

STM32MP25x lines

1. Article purpose[edit | edit source]

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[edit | edit source]

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)

Two instances of USB2PHY peripheral inside STM32MP25x lines :

USB2PHY1 connected to the USBH controller
USB2PHY2 connected to the USB3DR controller for USB2.0 speeds

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(s), and the STM32CubeMPU Package running on the Arm^® Cortex^®-M processor.

3.1. Boot time assignment[edit | edit source]

3.1.1. On STM32MP25x lines [edit | edit source]

One USB2PHY instance, i.e. USB2PHY2, is 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).

STM32MP2 internal peripherals assignment table template

| rowspan="2" | High speed interface
| rowspan="2" | 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[edit | edit source]

3.2.1. On STM32MP25x lines [edit | edit source]

STM32MP2 internal peripherals assignment table template

| rowspan="2" | High speed interface
| rowspan="2" | USB2PHY 
| USB2PHY1
| style="text-align:left;" | ⬚^OP-TEE
⬚^{TF-A BL31}
| ☐
| ⬚
| ☐
|
| Not a RIF aware, used as per allocation of USBH
|-
| USB2PHY2
| style="text-align:left;" | ☐^OP-TEE
☐^{TF-A BL31}
| ☐
| ☐
| ☐
|
| Not a RIF aware, used as per allocation of USB3DR
|-

|}

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

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
U-Boot: PHY uclass (drivers/phy/phy-uclass.c ) and driver (drivers/phy/phy-stm32-usb2femto.c )

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 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.