ADI Developer

For compile time configuration, it’s common Linux practice to keep board- and application-specific configuration out of the main driver file, instead putting it into the board support file.

For devices on custom boards, as typical of embedded and SoC-(system-on-chip) based hardware, Linux uses platform_data to point to board-specific structures describing devices and how they are connected to the SoC. This can include available ports, chip variants, preferred modes, default initialization, additional pin roles, and so on. This shrinks the board-support packages (BSPs) and minimizes board and application specific #ifdefs in drivers.

Declaring I2C devices

Unlike PCI or USB devices, I2C devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each I2C bus segment, and what address these devices are using. For this reason, the kernel code must instantiate I2C devices explicitly. There are different ways to achieve this, depending on the context and requirements. However the most common method is to declare the I2C devices by bus number.

This method is appropriate when the I2C bus is a system bus, as in many embedded systems, wherein each I2C bus has a number which is known in advance. It is thus possible to pre-declare the I2C devices that inhabit this bus. This is done with an array of struct i2c_board_info, which is registered by calling i2c_register_board_info().

So, to enable such a driver one need only edit the board support file by adding an appropriate entry to i2c_board_info.

For more information see: Documentation/i2c/instantiating-devices.rst

The I2C address of the SSM4567 depends on the setting of the ADDR pin.

ADDR	I2C Address
0	0x34
1	0x35

static struct i2c_board_info __initdata bfin_i2c_board_info[] = {
 
    [--snip--]
    {
        I2C_BOARD_INFO("ssm4567", 0x34),
    },
    [--snip--]
}

static int __init stamp_init(void)
{
    [--snip--]
    i2c_register_board_info(0, bfin_i2c_board_info,
                ARRAY_SIZE(bfin_i2c_board_info));
    [--snip--]
 
    return 0;
}
arch_initcall(board_init);

Devicetree

i2s: i2c@41600000 {
    compatible = "...;
    ...

    #size-cells = <0>;
    #address-cells = <1>;

    ssm4567: ssm4567@34 {
        compatible = "adi,ssm4567";
        reg = <0x34>;
    };
};

ASoC DAPM Widgets

Name	Description
OUT	Class-D Amplifier Output

ALSA Controls

Name	Description
DAC High Pass Filter Switch	Enables/Disables the high-pass filter for the DAC
DAC Low Power Switch	Enables/Disables low-power mode of the DAC
Master Playback Volume	Digital output volume control.
Low-EMI Switch	Enables/Disables low EMI mode.
Limiter Mode	Mode the output limiter is using.
Limiter Attack Rate	Attack rate of the output limiter.
Limiter Release Rate	Release rate of the output limiter.
Limiter Attack Threshold	Attack threshold for the output limiter.
Amplifier Boost Switch	Enables/Disables the output amplifier booster

DAI configuration

The amplifier driver registers one DAIs, one for each serial port. The DAI is named “ssm4567-hifi”

Supported DAI formats

Name	Supported by driver	Description
SND_SOC_DAIFMT_I2S	yes	I2S mode
SND_SOC_DAIFMT_RIGHT_J	no	Right Justified mode
SND_SOC_DAIFMT_LEFT_J	yes	Left Justified mode
SND_SOC_DAIFMT_DSP_A	yes	data MSB after FRM LRC
SND_SOC_DAIFMT_DSP_B	yes	data MSB during FRM LRC
SND_SOC_DAIFMT_AC97	no	AC97 mode
SND_SOC_DAIFMT_PDM	yes	Pulse density modulation
SND_SOC_DAIFMT_NB_NF	yes	Normal bit- and frameclock
SND_SOC_DAIFMT_NB_IF	yes	Normal bitclock, inverted frameclock
SND_SOC_DAIFMT_IB_NF	yes	Inverted frameclock, normal bitclock
SND_SOC_DAIFMT_IB_IF	yes	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

TDM configuration

If you want to use the SSM4567 in TDM mode you can configure it using snd_soc_dai_set_tdm_slot() from you ASoC board driver.

The following restrictions apply to the parameters of snd_soc_dai_set_tdm_slot().

tx_mask specifies the output channel mapping for the serial port. This must either be 0, or the same as rx_mask.
rx_mask specifies the input channel mapping for the serial port. There must be exactly one bit set in this mask which selects the slot that is used.
slots should be between 1 and 8
width must be either 32, 48, 64

Example:

static int ssm4567_link_init(struct snd_soc_pcm_runtime *rtd)
{
    int ret;
 
    ret = snd_soc_dai_set_tdm_slot(rtd->codec_dai, 0x01, 0x01, 8, 32);
    if (ret < 0)
        return ret;
 
    return 0;
}
 
static struct snd_soc_dai_link ssm4567_dai_link = {
    ...,
    .init = ssm4567_link_init,
};

Example DAI configuration

static const struct snd_soc_dapm_widget ssm4567_zed_widgets[] = {
    SND_SOC_DAPM_SPK("Speaker", NULL),
};
 
static const struct snd_soc_dapm_route ssm4567_zed_routes[] = {
    { "Speaker", NULL, "OUT" },
};
 
static struct snd_soc_dai_link ssm4567_zed_dai_link = {
    .name = "ssm4567",
    .stream_name = "ssm4567",
    .codec_dai_name = "ssm4567-hifi",
    .dai_fmt = SND_SOC_DAIFMT_DSP_A |
            SND_SOC_DAIFMT_NB_NF |
            SND_SOC_DAIFMT_CBS_CFS,
    .init = ssm4567_zed_init,
};
 
static struct snd_soc_card ssm4567_zed_card = {
    .name = "ZED SSM4567",
    .owner = THIS_MODULE,
    .dai_link = &zed_ssm4567_dai_link,
    .num_links = 1,
    .dapm_widgets = zed_ssm4567_widgets,
    .num_dapm_widgets = ARRAY_SIZE(zed_ssm4567_widgets),
    .dapm_routes = zed_ssm4567_routes,
    .num_dapm_routes = ARRAY_SIZE(zed_ssm4567_routes),
    .fully_routed = true,
};

Multi SSM4567 Example configuration

This example shows how to setup a ASoC board driver for a system with two SSM4567, one driving the left speaker and the other driving the right speaker. In this example the left SSM4567 is at I2C address 0x34 (ADDR=0) and the right SSM4567 is at I2S address 0x35 (ADDR=1).

Note support for multiple CODECs on a single DAI link requires Linux v3.17 or higher.

static int ssm4567_link_init(struct snd_soc_pcm_runtime *rtd)
{
    int ret;
 
    /* Slot 0 for left */
    ret = snd_soc_dai_set_tdm_slot(rtd->codec_dais[0], 0x01, 0x01, 2, 32);
    if (ret < 0)
        return ret;
 
    /* Slot 2 for right */
    ret = snd_soc_dai_set_tdm_slot(rtd->codec_dais[1], 0x02, 0x02, 2, 32);
    if (ret < 0)
        return ret;
 
    return 0;
}
 
static const struct snd_soc_dapm_widget ssm4567_zed_widgets[] = {
    SND_SOC_DAPM_SPK("Left Speaker", NULL),
    SND_SOC_DAPM_SPK("Right Speaker", NULL),
};
 
static const struct snd_soc_dapm_route ssm4567_zed_routes[] = {
    { "Left Speaker", NULL, "Left OUT" },
    { "Right Speaker", NULL, "Right OUT" },
};
 
static const snd_soc_dai_link_component ssm4567_zed_codec_components[] = {
    { /* Left */
        .name = "ssm4567.0-0034",
        .codec_dai_name = "ssm4567-hifi",
    },
    { /* Right */
        .name = "ssm4567.0-0035",
        .codec_dai_name = "ssm4567-hifi",
    },
 
};
 
/* Assign prefix to avoid name conflicts */
static const struct snd_soc_codec_conf ssm4567_zed_codec_conf[] = {
    {
        .dev_name = "ssm4567.0-0034",
        .name_prefix = "Left",
    },
    {
        .dev_name = "ssm4567.0-0035",
        .name_prefix = "Right",
    },
};
 
static struct snd_soc_dai_link ssm4567_zed_dai_link = {
    .name = "ssm4567",
    .stream_name = "ssm4567",
 
    .codecs = ssm4567_zed_codec_components,
    .num_codecs = ARRAY_SIZE(ssm4567_zed_codec_components),
    .codec_conf = ssm4567_zed_codec_conf,
    .num_configs = ARRAY_SIZE(ssm4567_zed_codec_conf),
 
    .dai_fmt = SND_SOC_DAIFMT_DSP_A |
        SND_SOC_DAIFMT_NB_NF |
        SND_SOC_DAIFMT_CBS_CFS,
    .init = ssm4567_link_init,
};
 
static struct snd_soc_card ssm4567_zed_card = {
    .name = "ZED SSM4567",
    .owner = THIS_MODULE,
    .dai_link = &zed_ssm4567_dai_link,
    .num_links = 1,
    .dapm_widgets = zed_ssm4567_widgets,
    .num_dapm_widgets = ARRAY_SIZE(zed_ssm4567_widgets),
    .dapm_routes = zed_ssm4567_routes,
    .num_dapm_routes = ARRAY_SIZE(zed_ssm4567_routes),
    .fully_routed = true,
};

More information

SSM4329 Linux Driver

SSM4567 Device Driver

Summary

Drivers

Supported Devices

Evaluation Boards

Source Code

Status

Files

Example device initialization