Jassi Brar Wrote:
> Sent: Tuesday, August 09, 2011 4:28 AM
> To: Boojin Kim
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-samsung-
> soc@xxxxxxxxxxxxxxx; Vinod Koul; Dan Williams; Kukjin Kim; Mark Brown;
> Grant Likely; Russell King; Liam Girdwood
> Subject: Re: [PATCH 14/15] ASoC: Samsung: Update DMA interface
>
> On Wed, Jul 27, 2011 at 11:01 AM, Boojin Kim <boojin.kim@xxxxxxxxxxx>
> 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.
You're right. I will remove it in next cleanup patch
>
> > 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.
Yes, This code makes the DMA position less accurately. But, This position is
enough for audio DMA activity. Other drivers also use similar method to get
the position.
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