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 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].
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):
- 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
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 ... regmap:regmap_reg_read regmap:regmap_reg_write
6. Source code location[edit source]
The TIM Linux driver source code is composed of:
- stm32-timers.c MFD driver to handle common resources: registers, clock, dmas.
- pwm-stm32.c PWM driver to handle PWM channel(s).
- stm32-timer-trigger.c IIO driver to handle trigger source for other internal peripherals and quadrature encoder interface.
- include/linux/mfd/stm32-timers.h and include/linux/iio/timer/stm32-timer-trigger.h header files
7. References[edit source]
- ↑ 1.0 1.1 1.2 1.3 TIM internal peripheral
- ↑ DMA_internal_peripheral
- ↑ ADC internal peripheral
- ↑ DAC internal peripheral
- ↑ DFSDM internal peripheral
- ↑ Incremental encoder Incremental encoder overview
- ↑ Debugfs
- ↑ Ftrace