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<noinclude>{{ApplicableFor | <noinclude>{{ApplicableFor | ||
|MPUs list=STM32MP13x, STM32MP15x | |MPUs list=STM32MP13x, STM32MP15x, STM32MP25x | ||
|MPUs checklist=STM32MP13x,STM32MP15x | |MPUs checklist=STM32MP13x,STM32MP15x, STM32MP25x | ||
}}</noinclude> | }}</noinclude> | ||
== Article purpose == | == Article purpose == | ||
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{{ReviewsComments|-- NathalieS , Fabrice G<br />Article to be updated to be compliant with ecosystem v2.1.0 (BZ 95795), some example on ''clock event'' must be added}} | {{ReviewsComments|-- NathalieS , Fabrice G<br />Article to be updated to be compliant with ecosystem v2.1.0 (BZ 95795), some example on ''clock event'' must be added}} | ||
{{ReviewsComments|-- [[User:Fabrice Gasnier|Fabrice Gasnier]] ([[User talk:Fabrice Gasnier|talk]]) 16:11, 16 October 2023 (CEST)<br />Could document here the OPTEE driver (similarly as done for [[ADC OpenSTLinux drivers]]) and update model to [[Contributors:OpenSTLinux_drivers_article_model]]. See Bz 163907.}} | |||
== Short description == | == Short description == | ||
The ''LPTIM''<ref name="LPTIM 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: | The ''LPTIM''<ref name="LPTIM 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: | ||
Revision as of 16:11, 16 October 2023
1. Article purpose[edit | edit source]
This article introduces the LPTIM Linux® driver for the LPTIM internal peripheral[1]:
- Which LPTIM 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 | edit source]
The LPTIM[1] Linux driver (kernel space) is based on the PWM, IIO and counter frameworks. It provides several functionalities:
MFD driver:
- handles common resources (registers, clock)
PWM driver:
- handles the PWM output channel (single channel)
IIO hardware trigger driver:
- handles hardware trigger sources (synchronously with PWM) for other internal peripherals such as ADC[2], DAC[3], DFSDM[4]
Counter driver:
- handles the quadrature encoder interface[5] as well as the external event counter.
3. Configuration[edit | edit source]
3.1. Kernel configuration[edit | edit source]
Activate the LPTIM[1] Linux driver in the kernel configuration using the Linux Menuconfig tool: Menuconfig or how to configure kernel.
Enable the following configurations (as well as their dependencies):
- CONFIG_MFD_STM32_LPTIMER
- CONFIG_PWM_STM32_LP
- CONFIG_IIO_STM32_LPTIMER_TRIGGER
- CONFIG_STM32_LPTIMER_CNT
Device Drivers ---> -> Multifunction device drivers ---> <*> Support for STM32 Low-Power Timer -> Pulse-width modulation (PWM) support ---> <*> STMicroelectronics STM32 PWM LP -> Industrial I/O support ---> -> Triggers - standalone ---> <*> STM32 Low-Power Timer Trigger -> Counter support ---> <*> STM32 LP Timer encoder counter driver
3.2. Device tree[edit | edit source]
Refer to the LPTIM device tree configuration article when configuring the LPTIM Linux kernel driver.
4. How to use[edit | 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 | edit source]
The LPTIM Linux driver can access LPTIM registers through REGMAP.
It comes with debugfs[6] entries, which allow dumping registers:
$ cd /sys/kernel/debug/regmap
$ ls
40004000.timer 40009000.timer
$ cd 40009000.timer
$ cat registers
000: 00000003
004: 00000000
008: 00000000
...
It also comes with tracepoints[7]:
$ cd /sys/kernel/debug/tracing
$ cat available_events | grep regmap
...
regmap:regmap_reg_read
regmap:regmap_reg_write
6. Source code location[edit | edit source]
The LPTIM Linux driver is composed of:
- stm32-lptimer.c driver to handle common resources, such as registers and clock.
- pwm-stm32-lp.c driver to handle PWM channel
- stm32-lptimer-trigger.c driver to handle trigger sources for other internal peripherals
- stm32-lptimer-cnt.c driver to handle quadrature encoder and external event counter
- include/linux/mfd/stm32-lptimer.h and include/linux/iio/timer/stm32-lptim-trigger.h header files
7. References[edit | edit source]