[alsa-devel] Simple-card without codec for testing purpose

[arnaud.mouiche at invoxia.com]

To answer to myself:
- there are some "virtual" codecs available : "bt-sco", 
"linux,spdif-dit" and "linux,spdif-dir". but none of them is fully generic.
- a "snd-soc-dummy-dai" codec is implemented in soc-utils.c. yet, no 
device-tree bindings are available, except if a patch like the following 
one is applied

--- a/sound/soc/soc-utils.c
+++ b/sound/soc/soc-utils.c
@@ -19,6 +19,7 @@
  #include <sound/pcm.h>
  #include <sound/pcm_params.h>
  #include <sound/soc.h>
+#include <linux/module.h>

  int snd_soc_calc_frame_size(int sample_size, int channels, int tdm_slots)
  {
@@ -151,9 +152,18 @@ static int snd_soc_dummy_remove(struct 
platform_device *pdev)
      return 0;
  }

+#ifdef CONFIG_OF
+static const struct of_device_id soc_dummy_ids[] = {
+    { .compatible = "linux,snd-soc-dummy", },
+    { }
+};
+MODULE_DEVICE_TABLE(of, soc_dummy_ids);
+#endif
+
  static struct platform_driver soc_dummy_driver = {
      .driver = {
          .name = "snd-soc-dummy",
+        .of_match_table = of_match_ptr(soc_dummy_ids),
      },
      .probe = snd_soc_dummy_probe,
      .remove = snd_soc_dummy_remove,



Once done, here is a DTS example for imx6sl:

&audmux {
     ssi3 {
         fsl,audmux-port = <6>;
         fsl,port-config = <
#ifdef SSI_TEST_MASTER
             0x00000000
#else
             (IMX_AUDMUX_V2_PTCR_TFSDIR |
             IMX_AUDMUX_V2_PTCR_TFSEL(4) |
             IMX_AUDMUX_V2_PTCR_TCLKDIR |
             IMX_AUDMUX_V2_PTCR_TCSEL(4))
#endif
             IMX_AUDMUX_V2_PDCR_RXDSEL(4)
         >;
     };

     port5 {
         fsl,audmux-port = <4>;
         fsl,port-config = <
#ifdef SSI_TEST_MASTER
             (IMX_AUDMUX_V2_PTCR_TFSDIR |
             IMX_AUDMUX_V2_PTCR_TFSEL(6) |
             IMX_AUDMUX_V2_PTCR_TCLKDIR |
             IMX_AUDMUX_V2_PTCR_TCSEL(6))
#else
             0x00000000
#endif
             IMX_AUDMUX_V2_PDCR_RXDSEL(6)
         >;
     };
};


&ssi3 {
     status = "okay";

     // select the a clock parent suitable for 48000 Hz sampling rate
     assigned-clocks = <&clks IMX6SL_CLK_SSI3_SEL>, <&clks IMX6SL_CLK_SSI3>;
     assigned-clock-parents = <&clks IMX6SL_CLK_PLL4_AUDIO_DIV>;
     assigned-clock-rates = <0>, <49152000>;
};

/ {
     codec_test: codec_test {
         compatible = "linux,snd-soc-dummy";
         #sound-dai-cells = <0>;
     };


     sound at 2 {
         compatible = "simple-audio-card";
         simple-audio-card,name = "test";
         simple-audio-card,format="dsp_a";

#ifdef SSI_TEST_MASTER
         simple-audio-card,frame-master = <&sound2_ssi>;
         simple-audio-card,bitclock-master = <&sound2_ssi>;
#else
         simple-audio-card,frame-master = <&codec_test>;
         simple-audio-card,bitclock-master = <&codec_test>;
#endif
             sound2_ssi: simple-audio-card,cpu {
                 sound-dai = <&ssi3>;
                 system-clock-frequency = <1536000>;
                 dai-tdm-slot-num = <2>;
                 dai-tdm-slot-width = <16>;
             };
             sound2codec: simple-audio-card,codec {
                 sound-dai = <&codec_test>;
             };
     };

};




Le 20/11/2015 02:24, Caleb Crome a écrit :
> I've been wondering about that too. I don't know how to do it easily.
>
> -Caleb
>
>
> On Thu, Nov 19, 2015 at 9:26 AM, arnaud.mouiche at invoxia.com
> <arnaud.mouiche at invoxia.com> wrote:
>> Hello,
>>
>> I'm starting debugging / testing all the fsl_ssi issues (see Caleb's
>> previous post).
>>
>> First step I just need to setup a DTS entry for  "simple-card" + fake codec
>> to generate arbitrary PCM bus output (1 to 16 channels, various TDM, various
>> sampling rate and format and master/slave role)
>> I will then plug my logical analyser, or do some loopback, or plug a FPGA to
>> generate/check some patterns.
>>
>> Is there such "fake codec" somewhere.  Indeed, something that look like the
>> bt-sco codec, but without rate/format/channel limitations ?
>> Or does the "simple-card" even needs one ?
>>
>> Regards,
>> Arnaud