查看“TIM Linux driver”的源代码

== Article purpose ==
This article introduces the TIM Linux<sup>&reg;</sup> driver for the TIM internal peripheral<ref name="TIM internal peripheral">[[TIM internal peripheral]]</ref>:
* 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.

== Short description ==
The ''TIM''<ref name="TIM internal peripheral"/> Linux driver (kernel space) is based on the [[PWM overview|PWM]] and [[IIO overview|IIO]] frameworks. It provides several functionalities:

'''MFD driver''':
* handles registers, clock and DMA<ref name="DMA internal peripheral">[[DMA_internal_peripheral]]</ref> 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<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 the '''quadrature encoder''' interface<ref>[https://en.wikipedia.org/wiki/Rotary_encoder#Incremental_encoder Incremental encoder] Incremental encoder overview</ref>.

== Configuration ==
=== Kernel configuration ===
Activate the TIM<ref name="TIM internal peripheral"/> 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 use ==
[[PWM_overview#How_to_use_PWM_with_sysfs_interface|How to use PWM with sysfs interface]]

[[How to use the IIO user space interface#How to set up a TIM or LPTIM trigger using the sysfs interface|How to set up a TIM or LPTIM trigger using the sysfs interface]]

[[How to use the IIO user space interface#How to use the quadrature encoder with the sysfs interface|How to use the quadrature encoder with the sysfs interface]]

== How to trace and debug ==
The ''TIM''<ref name="TIM internal peripheral"/> Linux driver can access the timer registers through REGMAP.

It comes with debugfs<ref name="debugfs">[[Debugfs]]</ref> 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<ref name="ftrace">[[Ftrace]]</ref>:
 $ 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:
* {{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/iio/trigger/stm32-timer-trigger.c | stm32-timer-trigger.c IIO driver}} to handle trigger source for other internal peripherals and 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

==References==
<references />

<noinclude>
[[Category:Timers]]
[[Category:IIO]]
{{PublicationRequestId | 9233 | 2018-10-15 | AnneJ}}
{{ArticleBasedOnModel | Linux driver article model}}
</noinclude>