SAI Linux driver

Article purpose

本文介绍了适用于SAI internal peripheral的SAI Linux^® 驱动程序。

Short Description

SAI Linux驱动程序是在Linux ALSA framework中实现的ASoC CPU DAI驱动程序。

Configuration

Kernel Configuration

使用Linux Menuconfig工具在内核配置中激活SAI Linux驱动程序： Menuconfig or how to configure kernel.

[*] Device Drivers
    [*] Sound card support
        [*] Advanced Linux Sound Architecture
            [*] ALSA for SoC audio support
                STMicroelectronics STM32 SOC audio support
	             [*] STM32 SAI interface (Serial Audio Interface) support

Device tree

配置SAI Linux内核驱动时，请参考SAI device tree configuration 文章。

How to use

可以通过ALSA设备从用户域访问SAI Linux驱动程序。有关如何列出和使用ALSA设备的信息，请参考ALSA overview 。

How to trace and debug

The 调试文件系统(debugfs) and procfs file system can be checked to get information on the SAI driver and the resources it uses. A non-exhaustive list of these file system entries is provided below. Refer to ALSA overview for more details on debugging tools.

• debugfs entries:

• asoc: refer to ALSA_overview#How_to_monitor
• clk: refer to Clock_overview#How_to_monitor_with_debugfs to get information on clocks.
• pinctrl: refer to Pinctrl_overview#How_to_monitor to get information on pins.
• regmap: allow to monitor SAI peripheral registers.

$ cat /sys/kernel/debug/regmap/xxx.audio-controller/registers

• procfs entries:

• asound: refer to ALSA_overview#How_to_debug
• interrupts: allow to check interrupts.

$ cat /proc/interrupts

Source code location

The STM32 SAI peripheral includes two independent audio subblocks that share common resources. The driver source code reflects this architecture.

sound/soc/stm/stm32_sai.c| |}} sound/soc/stm/stm32_sai.c : handles common resources such as clock, interrupt, reset and shared register.

sound/soc/stm/stm32_sai_sub.c| |}} sound/soc/stm/stm32_sai_sub.c : handles the resources dedicated to each subblock.

References