ADC Linux driver
目录
Article purpose
本文介绍了用于ADC [1]内部外围设备的Linux®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®驱动程序(内核空间)基于 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）。
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
Activate the ADC[1] Linux® driver in the kernel configuration using the Linux Menuconfig tool: Menuconfig or how to configure kernel (enable both CONFIG_STM32_ADC_CORE and CONFIG_STM32_ADC).
Device Drivers --->
<*> Industrial I/O support --->
Analog to digital converters --->
<*> STMicroelectronics STM32 adc core
<*> STMicroelectronics STM32 adc
Device tree
Refer to the ADC device tree configuration article when configuring the ADC Linux kernel driver.
How to use
In "IIO direct mode", the conversion result can be read directly from sysfs (refer to How to do a simple ADC conversion using the sysfs interface).
In "IIO triggered buffer mode", the configuration must be performed using sysfs first. Then, character device (/dev/iio:deviceX) is used to read data (refer to Convert one or more channels using triggered buffer mode).
How to trace and debug
Refer to How to trace with dynamic debug for how to enable the debug logs in the driver and in the framework.
Refer to 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 $> echo on > power/control # force the kernel to resume the ADC device (e.g. keep clocks and regulators enabled)
 |
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[2] usage can be verified by reading clk_summary:
Board $> 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[3] tree and usage can be verified (e.g. use count, open count or regulator reference voltage) as follows:
Board $> 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[4] usage can be verified by reading pinmux-pins:
Board $> cd /sys/kernel/debug/pinctrl/soc\:pin-controller@50002000/ Board $> cat pinmux-pins | grep adc pin 92 (PF12): device 48003000.adc function analog group PF12 # check pin is assigned to ADC and is configured as "analog"
- interrupts can be verified by reading "interrupts":
Board $> 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:
- drivers/iio/adc/stm32-adc-core.c | |}} stm32-adc-core driver to handle common resources such as clock (selection, prescaler), regulator used as reference voltage, interrupt and common registers.
- 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
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