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== Article purpose == | == Article purpose == | ||
This article introduces the TIM Linux<sup>®</sup> driver for the TIM internal peripheral<ref name="TIM internal peripheral">[[TIM internal peripheral]]</ref>: | This article introduces the TIM Linux<sup>®</sup> driver for the TIM internal peripheral<ref name="TIM internal peripheral">[[TIM internal peripheral]]</ref>: | ||
| Line 5: | Line 4: | ||
* How to configure, use and debug the driver | * How to configure, use and debug the driver | ||
* What is the driver structure, and where the source code can be found. | * What is the driver structure, and where the source code can be found. | ||
== Short description == | == Short description == | ||
The ''TIM''<ref name="TIM internal peripheral"/> Linux driver (kernel space) is based on the [[PWM overview|PWM]] | The ''TIM''<ref name="TIM internal peripheral"/> Linux driver (kernel space) is based on the [[PWM overview|PWM]], [[IIO overview|IIO]] and <span style="color: {{STLightBlue}};">counter</span> frameworks. It provides several functionalities: | ||
'''MFD driver''': | '''MFD driver''': | ||
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'''IIO driver''': | '''IIO driver''': | ||
* handles hardware '''trigger sources''' (synchronously with PWM) for other internal peripherals such as ADC<ref name="adc_internal">[[ADC internal peripheral]]</ref>, DAC<ref name="dac_internal">[[DAC internal peripheral]]</ref>, DFSDM<ref name="dfsdm_internal">[[DFSDM internal peripheral]]</ref>. | * handles hardware '''trigger sources''' (synchronously with PWM) for other internal peripherals such as ADC<ref name="adc_internal">[[ADC internal peripheral]]</ref>, DAC<ref name="dac_internal">[[DAC internal peripheral]]</ref>, DFSDM<ref name="dfsdm_internal">[[DFSDM internal peripheral]]</ref>. | ||
'''counter driver''': | |||
* handles the '''quadrature encoder''' interface<ref>[https://en.wikipedia.org/wiki/Rotary_encoder#Incremental_encoder Incremental encoder] Incremental encoder overview</ref>. | * handles the '''quadrature encoder''' interface<ref>[https://en.wikipedia.org/wiki/Rotary_encoder#Incremental_encoder Incremental encoder] Incremental encoder overview</ref>. | ||
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* CONFIG_PWM_STM32 | * CONFIG_PWM_STM32 | ||
* CONFIG_IIO_STM32_TIMER_TRIGGER | * CONFIG_IIO_STM32_TIMER_TRIGGER | ||
* CONFIG_STM32_TIMER_CNT | |||
Device Drivers ---> | Device Drivers ---> | ||
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-> Triggers - standalone ---> | -> Triggers - standalone ---> | ||
<*> STM32 timer trigger | <*> STM32 timer trigger | ||
-> Counter support ---> | |||
<*> STM32 Timer encoder counter driver | |||
=== Device tree === | === Device tree === | ||
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* {{CodeSource | Linux kernel | drivers/mfd/stm32-timers.c | stm32-timers.c MFD driver}} to handle common resources: registers, clock, dmas. | * {{CodeSource | Linux kernel | drivers/mfd/stm32-timers.c | stm32-timers.c MFD driver}} to handle common resources: registers, clock, dmas. | ||
* {{CodeSource | Linux kernel | drivers/pwm/pwm-stm32.c | pwm-stm32.c PWM driver}} to handle PWM channel(s). | * {{CodeSource | Linux kernel | drivers/pwm/pwm-stm32.c | pwm-stm32.c PWM driver}} to handle PWM channel(s). | ||
* {{CodeSource | Linux kernel | drivers/iio/trigger/stm32-timer-trigger.c | stm32-timer-trigger.c IIO driver}} to handle trigger source for other internal peripherals | * {{CodeSource | Linux kernel | drivers/iio/trigger/stm32-timer-trigger.c | stm32-timer-trigger.c IIO driver}} to handle trigger source for other internal peripherals. | ||
* {{CodeSource | Linux kernel | drivers/counter/stm32-timer-cnt.c | stm32-timer-cnt.c counter driver}} to handle the quadrature encoder interface. | |||
* {{CodeSource | Linux kernel | include/linux/mfd/stm32-timers.h}} and {{CodeSource | Linux kernel | include/linux/iio/timer/stm32-timer-trigger.h}} header files | * {{CodeSource | Linux kernel | include/linux/mfd/stm32-timers.h}} and {{CodeSource | Linux kernel | include/linux/iio/timer/stm32-timer-trigger.h}} header files | ||
Latest revision as of 15:55, 18 March 2021
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].
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
- CONFIG_STM32_TIMER_CNT
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
...
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.
- stm32-timer-cnt.c counter driver to handle the 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