TIM Linux driver

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Article purpose

本文介绍了用于TIM内部外围设备的TIM Linux® 驱动程序[1]:

  • 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

The TIM[1] Linux driver (kernel space) is based on the PWM and IIO frameworks. It provides several functionalities:

MFD driver:

  • handles registers, clock and DMA[2] resources
  • detects the TIM counter resolution, e.g. 16 or 32 bits.

PWM driver:

  • detects the number of TIM channels.
  • handles PWM output channels.
  • handles PWM capture channels (input). Note that the PWM capture relies on DMA, which is handled by the MFD core.

IIO driver:

  • handles hardware trigger sources (synchronously with PWM) for other internal peripherals such as ADC[3], DAC[4], DFSDM[5].
  • handles the quadrature encoder interface[6].

Configuration

Kernel configuration

Activate the TIM[1] 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 trace and debug

The TIM[1] Linux driver can access the timer registers through REGMAP.

It comes with debugfs[7] 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[8]:

$ 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:

References

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