Difference between revisions of "SPDIFRX Linux driver"

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1 Article purpose[edit]

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

2 Short Description[edit]

The SPDIFRX[1] Linux driver is an ASoC CPU DAI driver implemented in the Linux ALSA framework.

3 Configuration[edit]

3.1 Kernel Configuration[edit]

Activate the SPDIFRX[1] 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[edit]

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

4 How to use[edit]

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

The SPDFIRX driver exposes an alsa control, which allows to retrieve the IEC 958 status bits from the input audio stream. A sleep state can be configured for SPDIFRX input pin, in the device tree, to save power. If this sleep state is defined, the control can be used to retrieve IEC status bits, only when a record of the audio stream is active.

5 How to debug[edit]

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:
$ cat /sys/kernel/debug/regmap/xxx.audio-controller/registers
  • procfs entries:
$ cat /proc/interrupts

6 Source code location[edit]

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

7 References[edit]

<noinclude>

{{ArticleBasedOnModel | [[Linux driver article model]]}}
{{ArticleMainWriter | OlivierM}}
{{ ArticleApprovedVersion| OlivierM | ArnaudP |<No previous approved version>| BrunoB - 16Oct'18 - 9234 | 22Oct'18 }}

[[Category:ALSA]]</noinclude>


== Article purpose ==
This article introduces the SPDIFRX Linux<sup>&reg;</sup> driver for the [[SPDIFRX internal peripheral]].

== Short Description ==
The SPDIFRX<ref name="SPDIFRX internal peripheral">[[SPDIFRX internal peripheral]]</ref> Linux driver is an ASoC CPU DAI driver implemented in the Linux [[ALSA_overview|ALSA framework]].

== Configuration ==

=== Kernel Configuration ===
Activate the SPDIFRX<ref name="SPDIFRX internal peripheral"/> Linux driver in the kernel configuration using the Linux Menuconfig tool: [[Menuconfig or how to configure kernel]]<pre>

[*] 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</pre>


=== Device tree ===
Refer to the [[SPDIFRX device tree configuration]] article when configuring the SPDIFRX Linux kernel driver.

== How to use ==
The SAISPDIFRX driver is accessed from userland through an ALSA device. Refer to [[ALSA_overview#How_to_use|ALSA overview]] to see how to list and use ALSA devices.
The SPDFIRX driver exposes an alsa control, which allows to retrieve the IEC 958 status bits from
the input audio stream. A sleep state can be configured for SPDIFRX input pin, in the device tree, to save power. If this sleep state is defined, the control can be used to retrieve IEC status bits, only when a record of the audio stream is active.
== How to debug ==
The [[Debugfs|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#How_to_trace_and_debug_the_framework|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.<div style="margin-left: 2em;">

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

* procfs entries:
:* '''asound''': refer to [[ALSA_overview#How_to_debug]]
:* '''interrupts''': allow to check interrupts.<div style="margin-left: 2em;">

 $ cat /proc/interrupts</div>


== Source code location ==
{{CodeSource | Linux kernel | sound/soc/stm/stm32_spdifrx.c}}: implements the SPDIFRX driver.

==References==<references />
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== How to use ==
 
== How to use ==
The SAI driver is accessed from userland through an ALSA device. Refer to [[ALSA_overview#How_to_use|ALSA overview]] to see how to list and use ALSA devices.
+
The SPDIFRX driver is accessed from userland through an ALSA device. Refer to [[ALSA_overview#How_to_use|ALSA overview]] to see how to list and use ALSA devices.
  +
 
  +
The SPDFIRX driver exposes an alsa control, which allows to retrieve the IEC 958 status bits from
  +
the input audio stream. A sleep state can be configured for SPDIFRX input pin, in the device tree, to save power. If this sleep state is defined, the control can be used to retrieve IEC status bits, only when a record of the audio stream is active.
   
 
== How to debug ==
 
== How to debug ==