PMIC hardware components

1 Article purpose[edit]

The purpose of this article is to:

  • list the PMIC hardware components that might be integrated in the different boards
  • link these components to the corresponding software framework(s)
  • point to the datasheet(s) of these components
  • explain, when necessary, how to configure these components.

2 Software frameworks[edit]

Domain Peripheral Software frameworks Comment

PMIC STPMIC1 OP-TEE overview Regulator overview Watchdog overview U-Boot

3 STPMIC1[edit]

3.1 Description[edit]

The STPMIC1 is a device that handles the power supplies for some STM32MP boards. The STPMIC1 main features are:

  • configuration via I²C bus,
  • 10 regulators of different kinds with over-current protection,
  • 3 power switches for USB supplies,
  • a power-on key input,
  • a watchdog,
  • a thermal protection,
  • a NORMAL mode and an ALTERNATE mode that is used for system suspend.

The user manual is available here: NOT YET AVAILABLE

3.2 Support in Linux Kernel[edit]

The STPMIC1 driver is used to handle STPMIC1 Power Management Integrated Circuit (PMIC). The driver is composed of several parts:

  • The core driver
  • The regulator driver
  • The watchdog driver
  • The input driver

The thermal feature is not supported.

3.2.1 Core driver[edit]

The core implements the Multi-Function Devices Framework API.

  • It is probed by the I²C framework.
  • It handles communication with the PMIC via I²C.
  • It probes the others STPMIC1 drivers (input, watchdog....).
  • It acts as an interrupt controller for the other drivers.

Source code:


Bindings are described in:


3.2.2 Regulator driver[edit]

The driver implements the Regulator framework API

  • Each BUCK, LDO or POWER SWITCH inside the STPMIC1 device is presented as a voltage regulator.
  • Power switches are presented as fixed voltage sources. Voltage can not be set.
  • The driver does not handle the suspend configuration. This is done by the Secure Monitor.

Source code:


Bindings are described in:


3.2.3 Watchdog driver[edit]

The driver implements the Watchdog framework API

When enabled, a watchdog device is available for the user-land. As soon as a user has started to write in the watchdog it is armed in the PMIC. When the watchdog timer expires, the PMIC shuts down.

Source code:


Bindings are described in:


3.2.4 Input driver[edit]

The driver implements the Input framework API.

The driver exposes a single key (KEY_POWER) that can be used as any standard input device in /dev/input/eventX

Source code:


Bindings are described in:


3.2.5 Kernel Configuration[edit]

With kernel menuconfig, enable following configurations:

  • core part: MFD_STPMIC1
  • regulator: REGULATOR_STPMIC1
  • watchdog: STPMIC1_WATCHDOG

3.3 Support in U-BOOT[edit]

STPMIC1 is used by U-Boot to:

  • Control regulators used by other drivers (mmc-supply for SDCard for example, usb vbus)
  • Trace pmic startup reason

STMPIC is supported with existing uclass of the 'Driver Model' described in doc/driver-model/pmic-framework.rst .

The STPMIC1 is available with the existing commands:

  • pmic (CONFIG_CMD_PMIC)
  • regulator (CONFIG_CMD_REGULATOR)
  • poweroff (CONFIG_CMD_POWEROFF)

SPTMIC1 driver supports configuration via device-tree; the bindings, same as kernel, are described in:


3.4 Support in Cortex-A7 Secure[edit]

3.4.1 TF-A[edit]

STPMIC1 is used by TF-A firmware to:

  • Configure DDR power supplies.
  • Configure the regulators for system suspend and system shutdown.

Driver source code:


SPTMIC1 driver supports configuration via device-tree, bindings are described in:


An example of PMIC configuration with device tree can be found in this file, node &i2c4:


When using a PMIC on a board, TF-A is configured to use a secure I²C (I2C4 or I2C6). By default on STMicroelectronics boards, I2C4 is used.

Using another I²C (non-secure) is not supported in the TF-A implementation made by STMicroelectronics. But it is possible to modify the code and device tree files to support it.

Here is an example with I2C2:

  • Copy the chosen I²C node from Linux device tree in the TF-A device tree file for your board, as well as its dependencies (like pinctrl). You can also remove the properties not used by TF-A as done in the example below
/ {
	soc {
 +		i2c2: i2c@40013000 {
 +			compatible = "st,stm32mp15-i2c";
 +			reg = <0x40013000 0x400>;
 +			clocks = <&rcc I2C2_K>;
 +			resets = <&rcc I2C2_R>;
 +			#address-cells = <1>;
 +			#size-cells = <0>;
 +			status = "disabled";
 +		};
  • change pmic node parent to this newly added I²C
& i2c2 {
	pmic: stpmic@33 {   # You may also require to change this I²C address (33)
  • remove in PMIC node the property:
secure-status = "okay";
#define I2C2_BASE			U(0x40013000)
	case UART7_BASE:
	case UART8_BASE:
	case IWDG2_BASE:
+	case I2C2_BASE:
		/* Allow drivers to register some non secure resources */
		VERBOSE("IO for non secure resource 0x%x\n",
			(unsigned int)base);
  • Regarding the GPIO ports used by I2C2: in this stm32mp1_clk_gate[] table, remove the #ifdef IMAGE_BL2 around GPIO banks entries if present

3.4.2 OP-TEE[edit]

STPMIC1 is used by OP-TEE OS to configure the regulators for system suspend and system shutdown.

Driver source code: