DFSDM Linux driver
目录
Article purpose
本文的目的是介绍用于DFSDM internal peripheral的Linux®驱动程序：
- 驱动程序支持哪些DFSDM功能
- 如何配置，使用和调试它
- 驱动程序的结构是什么，在哪里可以找到源代码。
Short Description
DFSDM Linux®驱动程序(内核空间)基于 IIO 和 ALSA框架。 它提供多种模式：
- IIO直接模式: 在一个频道上进行单次捕获
- IIO软件缓冲区: 捕获一个或多个频道
-
IIO触发缓冲模式:使用触发器在一个或多个通道上捕获
它使用IIO中可用的硬件触发器。请参见TIM Linux driver and LPTIM Linux driver.
它提供了扩展的API[1] for audio usage which allows ，它允许通过SPI接口捕获PDM麦克风。
Configuration
Kernel configuration
通过使用menuconfig 工具，在内核配置中激活DFSDMLinux®驱动程序。
IIO driver
配置标志： CONFIG_STM32_DFSDM_ADC
Device Drivers --->
<*> Industrial I/O support --->
Analog to digital converters --->
<*> STMicroelectronics STM32 dfsdm adc
<*> STMicroelectronics STM32 adc # DFSDM ADC IIO driver
使用DFSDM ADC IIO驱动程序(仅限)时，用户还必须使能外部模拟前端的驱动程序(例如Sigma Delta调制器)。 例如，可以使用通用sigma delta调制器驱动程序(CONFIG_SD_ADC_MODULATOR):
Device Drivers --->
<*> Industrial I/O support --->
Analog to digital converters --->
<*> Generic sigma delta modulator # sigma delta modulator driver
Audio driver
配置标志： CONFIG_SND_SOC_STM32_DFSDM (注意：此配置取决于CONFIG_STM32_DFSDM_ADC)
Device Drivers --->
<*> Sound card support --->
<*> Advanced Linux Sound Architecture --->
<*> ALSA for SoC audio support --->
STMicroelectronics STM32 SOC audio support --->
<*> SoC Audio support for STM32 DFSDM # DFSDM Audio driver for digital microphone capture
Device tree
配置DFSDM Linux内核驱动程序时，请参考DFSDM device tree configuration 文章。
How to use
IIO driver
在 "'IIO直接模式"中，可以直接从sysfs中读取转换结果，请参见： 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来执行配置。 然后，使用字符设备(/dev/io：deviceX)读取数据，参见 For information on the standard IIO consumer interface, please refer to How to use IIO kernel API 给出了IIO使用者内核API的示例。
Audio driver
The DFSDM Linux driver can be accessed from userland through an ALSA device. Refer to ALSA overview for information on how to list and use ALSA devices.
How to trace and debug
How to monitor
The DFSDM driver uses resources such as clocks and GPIOs.
- Refer to Pinctrl_overview#How_to_monitor to check DFSDM GPIOs.
- Refer to Clock_overview#How_to_monitor_with_debugfs to check DFSDM clocks.
How to monitor with debugfs
The DFSDM registers are accessed using REGMAP by DFSDM Linux® driver.
It comes with 调试文件系统(debugfs) entries to dump registers:
$ cd /sys/kernel/debug/regmap/4400d000.dfsdm/ $ cat registers 000: 00000000 004: 00000000 008: 00000000
Other ways to monitor
- Man can check the DFSDM interrupts and/or the DFSDM DMA interrupts:
$ cat /proc/interrupts
CPU0 CPU1
...
99: 0 0 GIC-0 142 Level 4400d000.dfsdm:filter@0
100: 0 0 GIC-0 143 Level 4400d000.dfsdm:filter@1
101: 0 0 GIC-0 144 Level 4400d000.dfsdm:filter@2
...
How to trace
IIO driver
Refer to How to trace with dynamic debug for how to enable the debug logs in the driver and in the framework.
Board $> dmesg -n8 Board $> echo "file drivers/iio/adc/stm32-dfsdm* +p" > /sys/kernel/debug/dynamic_debug/control
To enable dynamic debug at boot time, append the following arguments on the kernel command line:
loglevel=8 dyndbg="file drivers/iio/adc/stm32-dfsdm* +p"
Audio driver
Refer to ALSA_overview#How_to_trace for details on trace tools.
How to debug
Audio driver
Refer to ALSA_overview#How_to_debug for details on debugging tools.
Source code location
It is composed of:
- drivers/iio/adc/stm32-dfsdm-core.c | |}} stm32-dfsdm-core.c , core part of DFSDM Linux driver to handle common resources: registers, clock
- drivers/iio/adc/stm32-dfsdm-adc.c | |}} stm32-dfsdm-adc.c , ADC part of DFSDM Linux driver to handle ADC operations
- sound/soc/stm/stm32_adfsdm.c | |}} stm32_adfsdm.c , ASoC DAI part of DFSDM Linux driver to handle audio operations
See also sigma delta modulator driver:
- drivers/iio/adc/sd_adc_modulator.c | |}} sd_adc_modulator.c , sigma delta modulator Linux driver to handle analog front-end
References
- ↑ include/linux/iio/adc/stm32-dfsdm-adc.h| |}} include/linux/iio/adc/stm32-dfsdm-adc.h , DFSDM IIO custom API
