Hi Fabio,

On Sun, Sep 22, 2013 at 11:05:03PM -0300, Fabio Estevam wrote:

Hi,

I am trying to do simultaneous capture and playback on mx6 wandboard and I noticed that it only works if I run 'aplay first'.

Here is the sequence that works:

1. aplay file.wav

2. Run 'alsamixer' and select line-in in the capture tab

3. Connect audio via line-in input

4. arecord -f cd -c 2 | aplay -f cd

Then I am able to hear the playback.

However, if I do not do step 1, and try to do the arecord/aplay directly I get:

$ arecord -f cd | aplay -f cd imx-sgtl5000 sound.13: set sample size in capture stream first

We can pinpoint the issue by the log "set sample size in":

450 if (synchronous) { 451 struct snd_pcm_runtime *first_runtime = 452 ssi_private->first_stream->runtime; 453 /* 454 * This is the second stream open, and we're in 455 * synchronous mode, so we need to impose sample 456 * sample size constraints. This is because STCCR is 457 * used for playback and capture in synchronous mode, 458 * so there's no way to specify different word 459 * lengths. 460 * 461 * Note that this can cause a race condition if the 462 * second stream is opened before the first stream is 463 * fully initialized. We provide some protection by 464 * checking to make sure the first stream is 465 * initialized, but it's not perfect. ALSA sometimes 466 * re-initializes the driver with a different sample 467 * rate or size. If the second stream is opened 468 * before the first stream has received its final 469 * parameters, then the second stream may be 470 * constrained to the wrong sample rate or size. 471 */ 472 if (!first_runtime->sample_bits) { 473 dev_err(substream->pcm->card->dev, 474 "set sample size in %s stream first\n", 475 substream->stream == 476 SNDRV_PCM_STREAM_PLAYBACK 477 ? "capture" : "playback"); 478 return -EAGAIN; 479 } 480 481 snd_pcm_hw_constraint_minmax(substream->runtime, 482 SNDRV_PCM_HW_PARAM_SAMPLE_BITS, 483 first_runtime->sample_bits, 484 first_runtime->sample_bits); 485 }

In freescale internal branch, I had a patch to drop this part of code because the hw_params() in fsl_ssi.c is already considering about the wl configuration, so it won't change the wl value even if two streams' sample bits are different.

But if we think about the benefit of snd_pcm_hw_constraint() for a case like "(arecord -d10 xx.wav &);sleep 1;aplay yy.wav", yea the non-simultaneous case, we might also just turn the dev_err() into dev_warn() from my point of view:

if (first_runtime->sample_bits) snd_pcm_hw_constraint_minmax(substream->runtime, SNDRV_PCM_HW_PARAM_SAMPLE_BITS, first_runtime->sample_bits, first_runtime->sample_bits); else dev_warn(substream->pcm->card->dev, "Not enforcing sample bits due to race\n");

You can try this two solutions and find a better one.

Best regards, Nicolin Chen

fsl-ssi-dai 2028000.ssi: ASoC: can't open interface 2028000.ssi: -11 ALSA lib pcm_dmix.c:1018:(snd_pcm_dmix_ open) unable to open slave aplay: main:660: audio open error: Device or resource busy Recording WAVE 'stdin' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo

I will try to debug this, but if anyone has any suggestions, please let me know.

Thanks,

Fabio Estevam