HDL AXI SPIDF

HDL AXI SPIDF Linux Driver.

Supported IP Cores

HDL AXI SPDIF

Source Code

Status

Source	Mainlined?
git	Yes

Files

Function	File
driver	sound/soc/adi/axi-spdif.c

Adding Linux driver support

Devicetree configuration

Example device initialization

The AXI SPDIF driver is a platform driver and can currently only be instantiated via device tree.

Required devicetree properties:

compatible: Should always be adi,axi-spdif-tx-1.00.a
reg: Base address and register area size
clocks: AXI bus clock and reference clock.
clock-names: axi and ref, respectively.
dmas: Transmit DMA channel.
dma-names: tx.

Example:

axi_spdif_tx_0: axi-spdif-tx@75c00000 {
    compatible = "adi,axi-spdif-tx-1.00.a";
    reg = <0x75c00000 0x1000>;
    clocks = <&clkc 15>, <&audio_clock>;
    clock-names = "axi", "ref";
    dmas = <&dmac_s 0>;
    dma-names = "tx";
};

Board integration

ADV7511 HDMI + SPDIF sound card

The HDL AXI SPDIF core is used in conjunction with the ADV7511 HDMI transmitter on various FPGA platforms. The sound card is described with the generic simple-audio-card binding, linking the AXI SPDIF CPU DAI with the ADV7511 HDMI audio codec DAI.

Kernel configuration

Device Drivers  --->
    <*> Sound card support  --->
        <*>   Advanced Linux Sound Architecture  --->
            <*>     ALSA for SoC audio support  --->
                <*>   Audio support for Analog Devices reference designs
                <*>     AXI-SPDIF support
                [--snip--]
                <*>   ASoC Simple sound card support
    Graphics support  --->
        Display Interface Bridges  --->
            <*> ADV7511 encoder
            [*]   ADV7511 HDMI Audio driver

Example device initialization

Required properties:

The AXI SPDIF node must define #sound-dai-cells = <0>.
The ADV7511 node must define #sound-dai-cells = <1>; DAI index 1 selects its SPDIF audio input.

Example (from arch/arm/boot/dts/xilinx/zynq-zed-adv7511.dtsi):

axi_spdif_tx_0: axi-spdif-tx@75c00000 {
    compatible = "adi,axi-spdif-tx-1.00.a";
    reg = <0x75c00000 0x1000>;
    dmas = <&dmac_s 0>;
    dma-names = "tx";
    clocks = <&clkc 15>, <&audio_clock>;
    clock-names = "axi", "ref";

    #sound-dai-cells = <0>;
};

adv7511_hdmi_snd {
    compatible = "simple-audio-card";
    simple-audio-card,name = "HDMI monitor";
    simple-audio-card,widgets =
        "Speaker", "Speaker";
    simple-audio-card,routing =
        "Speaker", "TX";

    simple-audio-card,dai-link@0 {
        cpu {
            sound-dai = <&axi_spdif_tx_0>;
            frame-master;
            bitclock-master;
        };
        codec {
            sound-dai = <&adv7511 1>;
        };
    };
};

Driver testing

Make sure the sound card is properly instantiated.

root:/> aplay -l
card 0: monitor [HDMI monitor], device 0: HDMI adv7511-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0

To test audio playback you can use the speaker-test utility, which allows to playback several different test patterns. For a extensive description on the speaker-test utility and the different options it supports please refer to the speaker-test man page.

root:/> speaker-test -c 2
speaker-test 1.0.24.2

Playback device is default
Stream parameters are 48000Hz, S16_LE, 2 channels
Using 16 octaves of pink noise
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 512 to 2097152
Period size range from 256 to 262143
Requested buffer time 20000 us
Periods = 4
was set period_size = 320
was set buffer_size = 960
 0 - Front Left
 1 - Front Right
....

This AXI SPDIF driver provides stereo S16_LE playback only. The following arecord and record-to-playback loopback examples require a separate capture device and do not test capture through this transmitter.

root:/> arecord -f S16 -r 48000 -c 2 > test.wav
...

To playback a wav file you can use the aplay utility. You can also create a audio loop-back by sending the output of arecord to aplay. This will send the incoming audio stream back via the outgoing audio stream.

root:/> arecord -f S16 -r 48000 -c 2 | aplay
...

For more information on the the aplay and arecord utilities please refer to the aplay and arecord man page.

More information

Need Help?

Analog Devices Linux Device Drivers Help Forum

Driver testing

DAI formats and clocks

DAI configuration

The driver will register one CPU-DAI named after the device itself.

Supported DAI formats

Name	Supported by driver	Description
SND_SOC_DAIFMT_I2S	no	I2S mode
SND_SOC_DAIFMT_RIGHT_J	no	Right Justified mode
SND_SOC_DAIFMT_LEFT_J	no	Left Justified mode
SND_SOC_DAIFMT_DSP_A	no	data MSB after FRM LRC
SND_SOC_DAIFMT_DSP_B	no	data MSB during FRM LRC
SND_SOC_DAIFMT_AC97	no	AC97 mode
SND_SOC_DAIFMT_PDM	no	Pulse density modulation
SND_SOC_DAIFMT_SPDIF	yes	SPDIF mode

SND_SOC_DAIFMT_NB_NF	yes	Normal bit- and frameclock
SND_SOC_DAIFMT_NB_IF	no	Normal bitclock, inverted frameclock
SND_SOC_DAIFMT_IB_NF	no	Inverted frameclock, normal bitclock
SND_SOC_DAIFMT_IB_IF	no	Inverted bit- and frameclock

SND_SOC_DAIFMT_CBM_CFM	no	Codec bit- and frameclock master
SND_SOC_DAIFMT_CBS_CFM	no	Codec bitclock slave, frameclock master
SND_SOC_DAIFMT_CBM_CFS	no	Codec bitclock master, frameclock slave
SND_SOC_DAIFMT_CBS_CFS	yes	Codec bit- and frameclock slave

Example DAI configuration

static struct snd_soc_dai_link hdmi_dai_link = {
    .name = "HDMI",
    .stream_name = "HDMI",
    .cpu_dai_name = "75c00000.axi-spdif-tx",
    .platform_name = "xilinx_pcm_audio.2",
    .codec_name = "adv7511.0-0039",
    .codec_dai_name = "adv7511",
    .dai_fmt = SND_SOC_DAIFMT_SPDIF |
            SND_SOC_DAIFMT_NB_NF |
            SND_SOC_DAIFMT_CBS_CFS,
};

static struct snd_soc_card hdmi_card = {
    .name = "HDMI monitor",
    .owner = THIS_MODULE,
    .dai_link = &hdmi_dai_link,
    .num_links = 1,
};