查看“ADC Linux driver”的源代码

== Article purpose ==
本文介绍了用于ADC <ref name="ADC internal peripheral">[[ADC internal peripheral]]</ref>内部外围设备的Linux<sup>&reg;</sup>驱动程序：
* 驱动程序支持哪些ADC功能
* 如何配置，使用和调试驱动程序
* 驱动程序的结构是什么，以及在哪里可以找到源代码。

== Short description ==
ADC Linux<sup>&reg;</sup>驱动程序(内核空间)基于 [[IIO overview|IIO]] 框架。
它支持两种模式：
# '''IIO直接模式'''：在通道上单次捕获（使用中断）
# '''IIO触发缓冲模式'''：在一个或多个通道上捕获（最好使用DMA）。<br/>它使用IIO中提供的硬件触发器。 请参阅[[TIM Linux driver]] and [[LPTIM Linux driver]].

== Configuration ==
=== Kernel configuration ===
使用Linux Menuconfig工具在内核配置中激活ADC <ref name="ADC internal peripheral"/> Linux<sup>&reg;</sup> 驱动程序: [[Menuconfig or how to configure kernel]] (同时启用CONFIG_STM32_ADC_CORE和CONFIG_STM32_ADC).
<pre>
Device Drivers  --->
   <*> Industrial I/O support  --->
      Analog to digital converters  --->
         <*> STMicroelectronics STM32 adc core
         <*>   STMicroelectronics STM32 adc
</pre>

=== Device tree ===
在配置ADC Linux内核驱动程序时，请参考[[ADC device tree configuration]] 文章。

== How to use ==
在“'''IIO直接模式'''”中，可以直接从'''sysfs'''读取转换结果 (请参阅
[[How to use the IIO user space interface#How to do a simple ADC conversion using the sysfs interface|How to do a simple ADC conversion using the sysfs interface]]).

在“'''IIO触发缓冲区模式'''”中，必须先使用'''sysfs'''执行配置。 然后，使用“字符设备”（/ dev / iio：deviceX）读取数据 (请参阅[[How to use the IIO user space interface#Convert one or more channels using triggered buffer mode|Convert one or more channels using triggered buffer mode]]).

== How to trace and debug ==
Refer to [[IIO_overview#How_to_trace_with_dynamic_debug|How to trace with dynamic debug]] for how to '''enable the debug logs''' in the driver and in the framework.

Refer to [[IIO_overview#How_to_debug_with_debugfs|How to debug with debugfs]] for how to '''access the ADC registers'''.

The ADC has system wide dependencies towards other key resources:
* '''runtime power management''' can be disabled, for example it may be forced '''on''' via ''power/control'' sysfs entry:
 {{Board$}} cd /sys/devices/platform/soc/48003000.adc/48003000.adc:adc@0
 {{Board$}} cat power/autosuspend_delay_ms
 2000
 {{Board$}} cat power/control
 auto                                     # kernel is allowed to automatically suspend the ADC device after autosuspend_delay_ms
 {{Board$}} {{highlight|echo on > power/control}}         # force the kernel to resume the ADC device (e.g. keep clocks and regulators enabled)
{{Info| It might be useful to disable runtime power management, in order to dump registers by any means or to check clock and regulator usage (see example below).}}

* '''clock'''<ref name="Clock overview">[[Clock overview]]</ref> usage can be verified by reading ''clk_summary'':
 {{Board$}} {{highlight|cat /sys/kernel/debug/clk/clk_summary}} | grep adc
          adc12_k                     1        1        0    24000000          0 0
                   adc12              1        1        0   196607910          0 0

* '''regulator'''<ref name="Regulator overview">[[Regulator overview]]</ref> tree and usage can be verified (e.g. use count, open count or regulator reference voltage) as follows:
 {{Board$}} {{highlight|cat /sys/kernel/debug/regulator/regulator_summary}}
  regulator                      use open bypass voltage current     min     max
 -------------------------------------------------------------------------------
     v3v3                          4    5      0  3300mV     0mA  3300mV  3300mV
        vdda                       1    2      0  2900mV     0mA  2900mV  2900mV 
           40017000.dac                                              0mV     0mV
           48003000.adc                                              0mV     0mV

* '''pinctrl'''<ref name="Pinctrl_overview">[[Pinctrl overview]]</ref> usage can be verified by reading ''pinmux-pins'':
 {{Board$}} cd /sys/kernel/debug/pinctrl/soc\:pin-controller@50002000/
 {{Board$}} {{highlight|cat pinmux-pins}} | grep adc
 pin 92 (PF12): device 48003000.adc function {{highlight|analog}} group PF12   # check pin is assigned to ADC and is configured as "analog"

* '''interrupts''' can be verified by reading "interrupts":
 {{Board$}} {{highlight|cat /proc/interrupts}}
            CPU0       CPU1
  56:          2          0     dummy   0 Edge      48003000.adc:adc@0

== Source code location ==
The ADC source code is composed of:
* {{CodeSource | Linux kernel | drivers/iio/adc/stm32-adc-core.c | stm32-adc-core driver}} to handle common resources such as clock (selection, prescaler), [[Regulator overview|regulator]] used as reference voltage, interrupt and common registers.
* {{CodeSource | Linux kernel | drivers/iio/adc/stm32-adc.c | stm32-adc driver}} to handle the resources available for each ADC such as  channel configuration and buffer handling.

==References==
<references />

<noinclude>
[[Category:IIO]]
{{PublicationRequestId | 9337 | 2018-10-23 | AnneJ}}
{{ArticleBasedOnModel | Linux driver article model}}
</noinclude>