TIM Linux driver

Article purpose

本文介绍了用于TIM内部外围设备的TIM Linux^® 驱动程序:

• 驱动程序支持哪些TIM功能
• 如何配置，使用和调试驱动程序
• 驱动程序的结构是什么，以及在哪里可以找到源代码。

Short description

Linux驱动程序（内核空间）“ TIM” 基于 PWM 和 IIO 框架。 它提供了几种功能：

MFD驱动程序:

• 处理寄存器，时钟和DMA资源
• 检测TIM计数器分辨率，例如 16或32位。

PWM驱动器:

• 检测TIM通道数。
• 处理PWM输出通道。
• 处理PWM捕捉通道（输入）。 请注意，PWM捕获依赖于由MFD内核处理的DMA。

IIO 驱动程序:

• 处理其他内部外围设备的硬件触发源(与PWM同步)，例如ADC , DAC, DFSDM.
• 处理‘正交编码器quadrature encoder interface.

Configuration

Kernel configuration

Activate the TIM Linux driver in the kernel configuration using the Linux Menuconfig tool: Menuconfig or how to configure kernel.

Enable the following configurations (and their dependencies):

• CONFIG_MFD_STM32_TIMERS
• CONFIG_PWM_STM32
• CONFIG_IIO_STM32_TIMER_TRIGGER

Device Drivers  --->
  -> Multifunction device drivers  --->
     <*> Support for STM32 Timers
  -> Pulse-width modulation (PWM) support  --->
     <*> STMicroelectronics STM32 PWM
  -> Industrial I/O support  --->
     -> Triggers - standalone  --->
        <*> STM32 timer trigger

Device tree

Refer to the TIM device tree configuration article when configuring the TIM Linux kernel driver.

How to use

How to use PWM with sysfs interface

How to set up a TIM or LPTIM trigger using the sysfs interface

How to use the quadrature encoder with the sysfs interface

How to trace and debug

The TIM Linux driver can access the timer registers through REGMAP.

It comes with debugfs entries, which allow dumping registers:

$ cd /sys/kernel/debug/regmap
$ ls
40004000.timer  44000000.timer

$ cd 44000000.timer
$ cat registers
000: 00000081
004: 00000000
008: 00000000
00c: 00000000
...

It also comes with tracepoints:

$ cd /sys/kernel/debug/tracing
$ cat available_events | grep regmap
...
regmap:regmap_reg_read
regmap:regmap_reg_write

Source code location

The TIM Linux driver source code is composed of:

• drivers/mfd/stm32-timers.c | |}} stm32-timers.c MFD driver to handle common resources: registers, clock, dmas.
• drivers/pwm/pwm-stm32.c | |}} pwm-stm32.c PWM driver to handle PWM channel(s).
• drivers/iio/trigger/stm32-timer-trigger.c | |}} stm32-timer-trigger.c IIO driver to handle trigger source for other internal peripherals and quadrature encoder interface.
• include/linux/mfd/stm32-timers.h| |}} include/linux/mfd/stm32-timers.h and include/linux/iio/timer/stm32-timer-trigger.h| |}} include/linux/iio/timer/stm32-timer-trigger.h header files

References

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