RTC overview

Applicable for

STM32MP13x lines, STM32MP15x lines

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This article gives information about the Linux^® RTC framework. The RTC framework is involved in precise time countdown.

1 Framework purpose

The RTC keeps the system time up-to-date and can wake up the system from the standby power mode at a programmed time.

A general presentation of the RTC framework is available in the Linux RTC documentation .

2 System overview

2.1 Component description

• RTC (hardware)

RTC dedicated hardware block in STM32MPU product.

• rtc-stm32

RTC ST driver.

• rtc

Linux RTC framework, it provides API to RTC driver and interfaces to user.

• Sysfs interface

Sysfs interface is accessible via /sys/class/rtc/rtcX/.

• Procfs interface

Procfs interface is accessible via /proc/driver/rtc.

• Char device interface

Device interface is accessible via /dev/rtcX.

• User application

The user application can be a user built application or an community application such as hwclock.

2.2 API description

API is described in Linux RTC documentation .

3 Configuration

3.1 Kernel configuration

Activate rtc-stm32 driver in kernel configuration using the Linux Menuconfig tool: Menuconfig or how to configure kernel

Device drivers  --->
    -*- Real Time Clock  --->
        <*> STM32 RTC

3.2 Device tree configuration

Refer to the RTC device tree configuration.

4 How to use the framework

Refer to the How to use the RTC.

5 How to trace and debug the framework

5.1 How to trace

Dynamic debug traces can be added using the following command:

echo -n 'file rtc-stm32.c +p'>/sys/kernel/debug/dynamic_debug/control

6 Source code location

• rtc-stm32: drivers/rtc/rtc-stm32.c
• api: include/linux/rtc.h
• framework:
  • drivers/rtc/class.c
  • drivers/rtc/dev.c
  • drivers/rtc/interface.c
  • drivers/rtc/lib.c
  • drivers/rtc/proc.c
  • drivers/rtc/sysfs.c
• device-tree bindings constants: include/dt-bindings/rtc/rtc-stm32.h