I2S Simple sound card issues from firmware version 6.6.20 and up

[rhysmorgan134]

Describe the bug

I have a dtoverlay utilising simple soundcard that has been working fine for some time. When the Pi5 was released I had some issues but resolved this by point the overlay to <&i2s_clk_consumer> and all was working well. Now since version 6.6.20 I get the following error with the same overlay that was working

[    6.398476] designware-i2s 1f000a4000.i2s: ASoC: error at snd_soc_dai_set_tdm_slot on 1f000a4000.i2s: -22
[    6.398485] designware-i2s 1f000a4000.i2s: simple-card: set_tdm_slot error
[    6.398487]  1f000a4000.i2s-dit-hifi: ASoC: error at snd_soc_link_init on 1f000a4000.i2s-dit-hifi: -22

The overlay in question is below

//Device tree overlay for generic stereo audio codec. ex) Asahi kasei AK4556
/dts-v1/;
/plugin/;

/ {
    compatible = "brcm,bcm2835";

    fragment@0 {
        target = <&sound>;
        __overlay__ {
            compatible = "simple-audio-card";
            simple-audio-card,name = "PiMost";
            status="okay";

            capture_link: simple-audio-card,dai-link@0 {
                format = "i2s";

                // Set RasPi to I2S slave
                bitclock-master = <&r_codec_dai>;
                frame-master = <&r_codec_dai>;

                r_cpu_dai: cpu {
                    sound-dai = <&i2s_clk_consumer>;

                // TDM slot configuration for stereo
                    dai-tdm-slot-num = <2>;
                    dai-tdm-slot-width = <16>;
                };

                r_codec_dai: codec {
                    sound-dai = <&codec_in>;
                };
            };

            playback_link: simple-audio-card,dai-link@1 {
                format = "i2s";

                // Set RasPi to I2S slave
                bitclock-master = <&p_codec_dai>;
                frame-master = <&p_codec_dai>;

                p_cpu_dai: cpu {
                    sound-dai = <&i2s_clk_consumer>;

                // TDM slot configuration for stereo
                    dai-tdm-slot-num = <2>;
                    dai-tdm-slot-width = <16>;
                };

                p_codec_dai: codec {
                    sound-dai = <&codec_out>;
                };
            };
        };
    };

    fragment@1 {
        target-path = "/";
        __overlay__ {
            codec_out: spdif-transmitter {
                #address-cells = <0>;
                #size-cells = <0>;
                #sound-dai-cells = <0>;
                /*
                    "linux,spdif-dit" is used in generic I2S(transmitter) driver.
                    You can see details "linux,spdif-dit" by bellow command
                    modinfo snd_soc_spdif_tx
                */
                compatible = "linux,spdif-dit";
                status = "okay";
            };
            codec_in: spdif-receiver {
                #address-cells = <0>;
                #size-cells = <0>;
                #sound-dai-cells = <0>;
                /*
                    "linux,spdif-dir" is used in generic I2S(receiver) driver.
                    You can see details "linux,spdif-dir" by bellow command
                    modinfo snd_soc_spdif_rx
                */
                compatible = "linux,spdif-dir";
                status = "okay";
            };
        };
    };

    fragment@2 {
        target = <&i2s_clk_consumer>;
        __overlay__ {
            #sound-dai-cells = <0>;
            status = "okay";
        };
    };
};

If I remove all occurances of these two lines then the overlay loads ok.

dai-tdm-slot-num = <2>;
dai-tdm-slot-width = <16>;

Is this expected? I am concerned as to whether it is going to cause issues by not specifying the channels and slot widths?

Thanks

Rhys

Steps to reproduce the behaviour

• Install overlay
• reboot the pi
• run dmesg | grep i2s
• see the error logs

Device (s)

Raspberry Pi 5

System

Raspberry Pi reference 2024-11-19
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 891df1e21ed2b6099a2e6a13e26c91dea44b34d4, stage4

Logs

[    6.398476] designware-i2s 1f000a4000.i2s: ASoC: error at snd_soc_dai_set_tdm_slot on 1f000a4000.i2s: -22
[    6.398485] designware-i2s 1f000a4000.i2s: simple-card: set_tdm_slot error
[    6.398487]  1f000a4000.i2s-dit-hifi: ASoC: error at snd_soc_link_init on 1f000a4000.i2s-dit-hifi: -22

Additional context

If I install this version of raspi-os then it all still works flawlessly

https://downloads.raspberrypi.org/raspios_arm64/images/raspios_arm64-2023-12-06/

[pelwell]

As of kernel 6.5, the driver for the I2S blocks found in RP1 has required between 0 and 16 slots of 32 bits, and that tx_mask and rx_mask are the same and not zero. More than that, there is code elsewhere in the driver that if the number of TDM slots is non-zero then the data width is forced to 32-bits.

In the kernel you say worked fine (6.1.x), the I2S driver had no set_tdm_slot method. By my reading, this means that snd_soc_dai_set_tdm_slot would return -ENOTSUPP, an error which does not result in a log message but also ends up doing nothing useful.

Have you tried without the TDM configuration? How does 2 channels of 16-bit TDM differ from regular 2 channel 16-bit usage?

[pelwell]

As far as I can tell, the RP1 I2S hardware has no explicit support for TDM mode: the WS clock always has a 50:50 duty cycle, and there is no support for arbitrary positioning of data within the frame. If it happened to work for you before then I think you don't actually need TDM mode. Which device are you interfacing to?

[rhysmorgan134]

Thanks Phil, I can confirm it works by removing all tdm references. I've done a bit of further research and reading since your first reply and it makes sense for it to be omitted.

It's talking to a MOST bus HAT I've developed that runs at 44.1khz or 48khz 2 Channel out and in (which from my new understanding tdm is not required), with the HAT acting as master and clock source coming from the fibre optic network.

Thanks a lot for your assistance with this, it's hugely appreciated!

[pelwell]

Thanks for the confirmation, and for forcing me to understand TDM mode.