Last edited one month ago

TIM Linux driver

Applicable for STM32MP13x lines, STM32MP15x lines, STM32MP25x lines

1. Article purpose[edit source]

This article introduces the TIM Linux® driver for the TIM internal peripheral[1]:

  • Which TIM features are supported by the driver
  • How to configure, use and debug the driver
  • What is the driver structure, and where the source code can be found.

2. Short description[edit source]

The TIM[1] Linux driver (kernel space) is based on the PWM, IIO and counter 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].

Counter driver:

  • handles the quadrature encoder interface[6].
  • counts on internal clock.

3. Configuration[edit source]

3.1. Kernel configuration[edit source]

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):

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
  -> Counter support  --->
     <*> STM32 Timer encoder counter driver

3.2. Device tree[edit source]

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

4. How to use[edit source]

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

5. How to trace and debug[edit source]

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

6. Source code location[edit source]

The TIM Linux driver source code is composed of:

7. References[edit source]