[PATCH 14/15] ASoC: Samsung: Update DMA interface

[Jassi Brar]

On Wed, Jul 27, 2011 at 11:01 AM, Boojin Kim <boojin.kim at samsung.com> wrote:

>  static void dma_enqueue(struct snd_pcm_substream *substream)
>  {
>        struct runtime_data *prtd = substream->runtime->private_data;
>        dma_addr_t pos = prtd->dma_pos;
>        unsigned int limit;
> -       int ret;
> +       struct samsung_dma_prep_info dma_info;
>
>        pr_debug("Entered %s\n", __func__);
>
> -       if (s3c_dma_has_circular())
> -               limit = (prtd->dma_end - prtd->dma_start) / prtd->dma_period;
> -       else
> -               limit = prtd->dma_limit;
> +       limit = (prtd->dma_end - prtd->dma_start) / prtd->dma_period;

'dma_limit' is rendered useless, so you might want to remove it from
'struct runtime_data'
as well.

>        pr_debug("%s: loaded %d, limit %d\n",
>                                __func__, prtd->dma_loaded, limit);
>
> -       while (prtd->dma_loaded < limit) {
> -               unsigned long len = prtd->dma_period;
> +       dma_info.cap = (samsung_dma_has_circular() ? DMA_CYCLIC : DMA_SLAVE);
> +       dma_info.direction =
> +               (substream->stream == SNDRV_PCM_STREAM_PLAYBACK
> +               ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
> +       dma_info.fp = audio_buffdone;
> +       dma_info.fp_param = substream;
> +       dma_info.period = prtd->dma_period;
> +       dma_info.len = prtd->dma_period*limit;
>
> +       while (prtd->dma_loaded < limit) {
>                pr_debug("dma_loaded: %d\n", prtd->dma_loaded);
>
> -               if ((pos + len) > prtd->dma_end) {
> -                       len  = prtd->dma_end - pos;
> -                       pr_debug("%s: corrected dma len %ld\n", __func__, len);
> +               if ((pos + dma_info.period) > prtd->dma_end) {
> +                       dma_info.period  = prtd->dma_end - pos;
> +                       pr_debug("%s: corrected dma len %ld\n",
> +                                       __func__, dma_info.period);
>                }
>
> -               ret = s3c2410_dma_enqueue(prtd->params->channel,
> -                       substream, pos, len);
> +               dma_info.buf = pos;
> +               prtd->params->ops->prepare(prtd->params->ch, &dma_info);
>
> -               if (ret == 0) {
> -                       prtd->dma_loaded++;
> -                       pos += prtd->dma_period;
> -                       if (pos >= prtd->dma_end)
> -                               pos = prtd->dma_start;
> -               } else
> -                       break;
> +               prtd->dma_loaded++;
> +               pos += prtd->dma_period;
> +               if (pos >= prtd->dma_end)
> +                       pos = prtd->dma_start;
>        }
>
>        prtd->dma_pos = pos;
>  }
>
> -static void audio_buffdone(struct s3c2410_dma_chan *channel,
> -                               void *dev_id, int size,
> -                               enum s3c2410_dma_buffresult result)
> +static void audio_buffdone(void *data)
>  {
> -       struct snd_pcm_substream *substream = dev_id;
> -       struct runtime_data *prtd;
> +       struct snd_pcm_substream *substream = data;
> +       struct runtime_data *prtd = substream->runtime->private_data;
>
>        pr_debug("Entered %s\n", __func__);
>
> -       if (result == S3C2410_RES_ABORT || result == S3C2410_RES_ERR)
> -               return;
> -
> -       prtd = substream->runtime->private_data;
> +       if (prtd->state & ST_RUNNING) {
> +               prtd->dma_pos += prtd->dma_period;
> +               if (prtd->dma_pos >= prtd->dma_end)
> +                       prtd->dma_pos = prtd->dma_start;
>
> -       if (substream)
> -               snd_pcm_period_elapsed(substream);
> +               if (substream)
> +                       snd_pcm_period_elapsed(substream);
>
> -       spin_lock(&prtd->lock);
> -       if (prtd->state & ST_RUNNING && !s3c_dma_has_circular()) {
> -               prtd->dma_loaded--;
> -               dma_enqueue(substream);
> +               spin_lock(&prtd->lock);
> +               if (!samsung_dma_has_circular()) {
> +                       prtd->dma_loaded--;
> +                       dma_enqueue(substream);
> +               }
> +               spin_unlock(&prtd->lock);
>        }
> -
> -       spin_unlock(&prtd->lock);
>  }

Since we set integer-constraint on number of periods, you could also
discard bothering fractional boundaries. That would make things a lot
simpler.



> @@ -265,14 +250,14 @@ static int dma_trigger(struct snd_pcm_substream *substream, int cmd)
>        case SNDRV_PCM_TRIGGER_RESUME:
>        case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
>                prtd->state |= ST_RUNNING;
> -               s3c2410_dma_ctrl(prtd->params->channel, S3C2410_DMAOP_START);
> +               prtd->params->ops->trigger(prtd->params->ch);
>                break;
>
>        case SNDRV_PCM_TRIGGER_STOP:
>        case SNDRV_PCM_TRIGGER_SUSPEND:
>        case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
>                prtd->state &= ~ST_RUNNING;
> -               s3c2410_dma_ctrl(prtd->params->channel, S3C2410_DMAOP_STOP);
> +               prtd->params->ops->stop(prtd->params->ch);
>                break;

I wish you agreed and used
       prtd->params->ops->cmd(ch, enum some_cmd_options)
rather than having 4 separate callbacks
      prtd->params->ops->trigger(prtd->params->ch)
      prtd->params->ops->stop(prtd->params->ch)
     prtd->params->ops->flush(prtd->params->ch)
     prtd->params->ops->started(prtd->params->ch)


> @@ -291,21 +276,12 @@ dma_pointer(struct snd_pcm_substream *substream)
>        struct snd_pcm_runtime *runtime = substream->runtime;
>        struct runtime_data *prtd = runtime->private_data;
>        unsigned long res;
> -       dma_addr_t src, dst;
>
>        pr_debug("Entered %s\n", __func__);
>
> -       spin_lock(&prtd->lock);
> -       s3c2410_dma_getposition(prtd->params->channel, &src, &dst);
> -
> -       if (substream->stream == SNDRV_PCM_STREAM_CAPTURE)
> -               res = dst - prtd->dma_start;
> -       else
> -               res = src - prtd->dma_start;
> -
> -       spin_unlock(&prtd->lock);
> +       res = prtd->dma_pos - prtd->dma_start;
>
> -       pr_debug("Pointer %x %x\n", src, dst);
> +       pr_debug("Pointer offset: %lu\n", res);
>
>        /* we seem to be getting the odd error from the pcm library due
>         * to out-of-bounds pointers. this is maybe due to the dma engine

Isn't this a regression ?
dma_pointer() doesn't really return actual location of DMA activity anymore.
Now it simply tells the last period done.
This would affect latencies in a bad way.