ARM: S3C: Add info for supporting circular DMA buffers

The S3C64XX DMA implementation will work a lot better with the ability
to enqueue circular buffers as the hardware can do it's own linked-list
management.

Add a function s3c_dma_has_circular() to show that the system can do this
and a flag for the channel.

Update the s3c24xx/s3c64xx I2S DMA code to deal with this.

Signed-off-by: Ben Dooks <ben@simtec.co.uk>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Acked-by: Mark Brown <broonie@@opensource.wolfsonmicro.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/sound/soc/s3c24xx/s3c24xx-pcm.c b/sound/soc/s3c24xx/s3c24xx-pcm.c
index 5cbbdc80fde3..1f35c6fcf5fd 100644
--- a/sound/soc/s3c24xx/s3c24xx-pcm.c
+++ b/sound/soc/s3c24xx/s3c24xx-pcm.c
@@ -75,11 +75,19 @@ static void s3c24xx_pcm_enqueue(struct snd_pcm_substream *substream)
 {
         struct s3c24xx_runtime_data *prtd = substream->runtime->private_data;
         dma_addr_t pos = prtd->dma_pos;
+        unsigned int limit;
         int ret;
 
         pr_debug("Entered %s\n", __func__);
 
-        while (prtd->dma_loaded < prtd->dma_limit) {
+        if (s3c_dma_has_circular()) {
+                limit = (prtd->dma_end - prtd->dma_start) / prtd->dma_period;
+        } else
+                limit = prtd->dma_limit;
+
+        pr_debug("%s: loaded %d, limit %d\n", __func__, prtd->dma_loaded, limit);
+
+        while (prtd->dma_loaded < limit) {
                 unsigned long len = prtd->dma_period;
 
                 pr_debug("dma_loaded: %d\n", prtd->dma_loaded);
@@ -123,7 +131,7 @@ static void s3c24xx_audio_buffdone(struct s3c2410_dma_chan *channel,
                 snd_pcm_period_elapsed(substream);
 
         spin_lock(&prtd->lock);
-        if (prtd->state & ST_RUNNING) {
+        if (prtd->state & ST_RUNNING && !s3c_dma_has_circular()) {
                 prtd->dma_loaded--;
                 s3c24xx_pcm_enqueue(substream);
         }
@@ -164,6 +172,11 @@ static int s3c24xx_pcm_hw_params(struct snd_pcm_substream *substream,
                         printk(KERN_ERR "failed to get dma channel\n");
                         return ret;
                 }
+
+                /* use the circular buffering if we have it available. */
+                if (s3c_dma_has_circular())
+                        s3c2410_dma_setflags(prtd->params->channel,
+                                             S3C2410_DMAF_CIRCULAR);
         }
 
         s3c2410_dma_set_buffdone_fn(prtd->params->channel,