1. Article purpose[edit | edit source]
The purpose of this article is to:
- briefly introduce the PWR 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 PWR peripheral is used to control the device power supply configuration.
It has 6 input pins (named wakeup pins) which can be programmed to wake the system up from low power. The wakeup pins are listed with WKUP prefix in the STM32MP15 Datasheet.
These pins can be used by the Cortex®-A7 non secure (via Cortex®-A7 secure services) or the Cortex®-M4.
The PWR peripheral provides 2 output hardware lines named PWR_ON and PWR_LP:
- In STPMIC1 configuration, PWR_ON allows to select the register bank (active or low power). PWR_LP is not used.
- In the power discrete solution they drive VDDcore which feeds the Cortex®-A7, the Cortex®-M4 and the peripherals. They also control the DDR power supplies (VDD_DDR, VREF_DDR, VTT_DDR).
Refer to the STM32MP15 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 STM32MP15x lines 
[edit | edit source]
The PWR is closely configured together with RCC by all the boot components: the ROM code, the FSBL, the SSBL and up to Linux® kernel. Its configuration is carried by the device tree.
Click on the right to expand the legend...
Check boxes illustrate the possible peripheral allocations supported by STM32 MPU Embedded Software:
- ☐ means that the peripheral can be assigned (☑) to the given boot time context.
- ⬚ means that the peripheral can be assigned to the given boot time context, but this configuration is not supported in STM32 MPU Embedded Software distribution.
- ✓ is used for system peripherals that cannot be unchecked because they are statically 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-A7 secure (ROM code) |
Cortex-A7 secure (TF-A BL2) |
Cortex-A7 non-secure (U-Boot) | |||
| Power & Thermal | PWR | PWR | ✓ | ✓ | ✓ | |
3.2. Runtime assignment[edit | edit source]
3.2.1. On STM32MP15x lines [edit | edit source]
Click on the right to expand the legend...
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.
- ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in STM32 MPU Embedded Software distribution.
- ✓ 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 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 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) | |||
| Power & Thermal | PWR | PWR | ✓ | ✓ | ✓ | |
4. Software frameworks and drivers[edit | edit source]
Below are listed the software frameworks and drivers managing the PWR peripheral for the embedded software components listed in the above tables.
- Linux®: regulator framework and interrupt framework
- OP-TEE:
- U-Boot: arch/arm/mach-stm32mp/pwr_regulator.c
- STM32Cube: PWR HAL driver
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:
6. How to go further[edit | edit source]
The PWR is interfaced with the hardware debug port (HDP) of the STM32MP15. This link offers the flexibility to observe the main PWR state signals on debug pins.
Please refer to STM32MP15 reference manuals for the exact list of signals that can be monitored.
Arm® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere. 
Arm® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.