SPDIFRX Linux driver

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1 Article purpose

This article introduces the SPDIFRX Linux^® driver for the SPDIFRX internal peripheral.

2 Short Description

The SPDIFRX Linux driver is an ASoC CPU DAI driver implemented in the Linux ALSA framework.

3 Configuration

3.1 Kernel Configuration

Activate the SPDIFRX Linux driver in the kernel configuration using the Linux Menuconfig tool: 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 S/PDIF receiver (SPDIFRX) support

3.2 Device tree

Refer to the SPDIFRX device tree configuration article when configuring the SPDIFRX Linux kernel driver.

4 How to use

The SAI driver is accessed from userland through an ALSA device. Refer to ALSA overview to see how to list and use ALSA devices.

5 How to debug

The debugfs and procfs file systems can be checked to get information about the SPDFIRX driver and the resources it uses. A none exhaustive list of these file system entries is provided below. Refer to ALSA overview to get more details about 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 SPDIFRX 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

6 Source code location

sound/soc/stm/stm32_spdifrx.c : implements the SPDIFRX driver.