On 03/23/2013 02:28 PM, Laxman Dewangan wrote:

On Saturday 23 March 2013 06:59 PM, Lars-Peter Clausen wrote:

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On 03/23/2013 02:16 PM, Laxman Dewangan wrote:

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On Saturday 23 March 2013 05:05 AM, Stephen Warren wrote:

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On 03/22/2013 10:26 AM, Lars-Peter Clausen wrote:

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Hi,

The tegra pcm driver tries to emulate SNDRV_PCM_TRIGGER_PAUSE and SNDRV_PCM_TRIGGER_RESUME. By passing SNDRV_PCM_TRIGGER_START and SNDRV_PCM_TRIGGER_STOP to snd_dmaengine_pcm_trigger. But does this really work? The old non-dmaengine based driver implemented this properly. I'd reset the dma position pointer for SNDRV_PCM_TRIGGER_START, but keep it where it was for SNDRV_PCM_TRIGGER_RESUME. But as far as I can see with the dmaengine based driver the pointer always gets reset to 0 for both SNDRV_PCM_TRIGGER_START and SNDRV_PCM_TRIGGER_RESUME.

It's quite possible this hasn't been tested, or tested recently. I don't recall how to test PAUSE/RESUME. Can you enlighten me?

Laxman, can you comment here?

The tegra20/Tegra30 does not support the pause of the channel. It was through global pause. hence the pause and resume is implemented like stop transfer and again restart transfer. hence you are seeing this as the reset pointer as 0.

Yea, but in that case you shouldn't implement pause/resume at all. You've changed the semantics on pause/resume on which applications rely. If pause/resume are not implemented applications usually workaround it.

• Lars

So should we return -EINVAL in case of following?

    case SNDRV_PCM_TRIGGER_RESUME:
    case SNDRV_PCM_TRIGGER_PAUSE_PUSH:

Don't set the SNDRV_PCM_INFO_PAUSE and SNDRV_PCM_INFO_RESUME bits in the pcm_hardware struct and use snd_dmaengine_pcm_trigger as your trigger callback. The ALSA core will take care of everything else.

- Lars