PMIC hardware components

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1 Article purpose

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

Internal peripherals software table template

| PMIC
| STPMIC1
| OP-TEE overview
| Regulator overview  Watchdog overview
| 
|
|-
|}

3 STPMIC1

3.1 Description

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

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

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/stpmic1.txt 

3.2.2 Regulator driver

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/stpmic1-regulator.txt 

3.2.3 Watchdog driver

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/stpmic1-wdt.txt 

3.2.4 Input driver

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/stpmic1-onkey.txt 

3.2.5 Kernel Configuration

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

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.txt .

• pmic :
  • uclass: drivers/power/regulator/regulator-uclass.c , CONFIG_DM_PMIC
  • driver: drivers/power/pmic/stpmic1.c , CONFIG_PMIC_STPMIC1
• regulator:
  • uclass: drivers/power/pmic/pmic-uclass.c , CONFIG_DM_REGULATOR
  • driver: drivers/power/regulator/stpmic1.c , CONFIG_DM_REGULATOR_STPMIC1
• sysreset:
  • uclass: drivers/sysreset/sysreset-uclass.c , CONFIG_SYSRESET
  • code in pmic driver

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:

doc/device-tree-bindings/mfd/stpmic1.txt

3.4 Support in Cortex-A7 Secure

3.4.1 TF-A

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/fdts/stm32mp/st,stpmic1.txt 

3.4.2 OP-TEE

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