[alsa-devel] [ASoC]Changing the order of trigger in soc_pcm_trigger

[Liam Girdwood]

On Wed, 2007-06-06 at 18:36 +0530, Nobin Mathew wrote:
> Liam,
> 
> I have one suggestion.
> 
> Can we use this
> 
> if (rtd->codec_dai->ops.trigger) {
> 		ret = rtd->codec_dai->ops.trigger(substream, cmd);
> 		if (ret < 0)
> 			return ret;
> 	}
> 
> if (rtd->cpu_dai->ops.trigger) {
> 	ret = rtd->cpu_dai->ops.trigger(substream, cmd);
> 	if (ret < 0)
> 		return ret;
> }
> if (platform->pcm_ops->trigger) {
> 	ret = platform->pcm_ops->trigger(substream, cmd);
> 	if (ret < 0)
> 		return ret;
> }
> 
> Instead of
> 
> if (rtd->codec_dai->ops.trigger) {
> 		ret = rtd->codec_dai->ops.trigger(substream, cmd);
> 		if (ret < 0)
> 			return ret;
> 	}
> 
> if (platform->pcm_ops->trigger) {
> 	ret = platform->pcm_ops->trigger(substream, cmd);
> 	if (ret < 0)
> 		return ret;
> }
> 
> if (rtd->cpu_dai->ops.trigger) {
> 	ret = rtd->cpu_dai->ops.trigger(substream, cmd);
> 	if (ret < 0)
> 		return ret;
> }
> 
> 
> That means trigger the Cpu before pcm. Because most of the controllers
> needs to be initialized and triggered before external DMA is
> triggered.
> 
> Correct me if i am going wrong.


The current ordering allows the DMA to trigger before the I2S/PCM
controller triggers. This means that the DMA should be ready before the
controller generates any FIFO DMA interrupt requests. Fwiw, this seems
to work well on most machines atm. 

> This was causing so many problems in my hardware.

What sort of problems. Underruns ? What does your trigger do in each
case ?

Is it possible to set some of your controller up in prepare() and then
hit it's enable bit in trigger ?

Liam