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
Cortex-A7
secure
(OP-TEE)
Cortex-A7
non-secure
(Linux)
Cortex-M4

(STM32Cube)
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:

 include/linux/mfd/stpmic1.h  
 drivers/mfd/stpmic1.c  


Bindings are described in:

 Documentation/devicetree/bindings/mfd/st,stpmic1.txt 

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:

 drivers/regulator/stpmic1_regulator.c  

Bindings are described in:

 Documentation/devicetree/bindings/regulator/st,stpmic1-regulator.txt 

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:

 drivers/watchdog/stpmic1_wdt.c  

Bindings are described in:

 Documentation/devicetree/bindings/watchdog/st,stpmic1-wdt.txt 

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:

 drivers/input/misc/stpmic1_onkey.c 

Bindings are described in:

 Documentation/devicetree/bindings/input/st,stpmic1-onkey.txt 

3.2.5 Kernel Configuration[edit]

With kernel menuconfig, enable following configurations:

  • core part: MFD_STPMIC1
  • regulator: REGULATOR_STPMIC1
  • watchdog: STPMIC1_WATCHDOG
  • input: INPUT_STPMIC1_ONKEY

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:

 Documentation/devicetree/bindings/regulator/st,stpmic1-regulator.txt 

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:

 include/drivers/st/stpmic1.h  
 drivers/st/pmic/stpmic1.c  

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

 docs/devicetree/bindings/power/st,stpmic1.txt 

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

 fdts/stm32mp15xx-edx.dtsi 

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
+		i2c2: i2c@40013000 {
+			compatible = "st,stm32f7-i2c";
+			reg = <0x40013000 0x400>;
+			interrupt-names = "event", "error";
+			interrupts = <GIC_SPI 33 IRQ_TYPE_LEVEL_HIGH>,
+				     <GIC_SPI 34 IRQ_TYPE_LEVEL_HIGH>;
+			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)
	...
};
#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);

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:

 core/include/drivers/stpmic1.h  
 core/drivers/stpmic1.c 


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