ASoC: Samsung: Do not queue cyclic buffers multiple times

The legacy S3C-DMA API required every period of a cyclic buffer to be
queued separately. After conversion of Samsung ASoC to Samsung DMA
wrappers somebody made an assumption that the same is needed for DMA
engine API, which is not true.

In effect, Samsung ASoC DMA code was queuing the whole cyclic buffer
multiple times with a shift of one period per iteration, leading to:
  a) severe memory waste - up to 13x times more DMA transfer descriptors
     are allocated than needed,
  b) possible memory corruption, because further cyclic buffers were out
     of the original buffers, due to the offset.

This patch fixes this problem by making the legacy S3C-DMA API use the
same semantics as DMA engine (the whole cyclic buffer is enqueued at
once) and modifying users of Samsung DMA wrappers in cyclic mode to
behave appropriately.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mark Brown <broonie@linaro.org>

diff --git a/arch/arm/plat-samsung/s3c-dma-ops.c b/arch/arm/plat-samsung/s3c-dma-ops.c
index 0cc40aea3f5adbd9a78ff8557f246f476d1b97e2..98b10ba67dc7c84e423be91cf1b868cc422908f1 100644 (file)
--- a/arch/arm/plat-samsung/s3c-dma-ops.c
+++ b/arch/arm/plat-samsung/s3c-dma-ops.c
@@ -82,7 +82,8 @@ static int s3c_dma_config(unsigned ch, struct samsung_dma_config *param)
 static int s3c_dma_prepare(unsigned ch, struct samsung_dma_prep *param)
 {
        struct cb_data *data;
-       int len = (param->cap == DMA_CYCLIC) ? param->period : param->len;
+       dma_addr_t pos = param->buf;
+       dma_addr_t end = param->buf + param->len;
 
        list_for_each_entry(data, &dma_list, node)
                if (data->ch == ch)
@@ -94,7 +95,15 @@ static int s3c_dma_prepare(unsigned ch, struct samsung_dma_prep *param)
                data->fp_param = param->fp_param;
        }
 
-       s3c2410_dma_enqueue(ch, (void *)data, param->buf, len);
+       if (param->cap != DMA_CYCLIC) {
+               s3c2410_dma_enqueue(ch, (void *)data, param->buf, param->len);
+               return 0;
+       }
+
+       while (pos < end) {
+               s3c2410_dma_enqueue(ch, (void *)data, pos, param->period);
+               pos += param->period;
+       }
 
        return 0;
 }

diff --git a/sound/soc/samsung/dma.c b/sound/soc/samsung/dma.c
index a0c67f60f594cdcc1af41958d3c8efa199b9c98d..9338d11e92168c222eae4630228f711bd9cf803c 100644 (file)
--- a/sound/soc/samsung/dma.c
+++ b/sound/soc/samsung/dma.c
@@ -90,6 +90,13 @@ static void dma_enqueue(struct snd_pcm_substream *substream)
        dma_info.period = prtd->dma_period;
        dma_info.len = prtd->dma_period*limit;
 
+       if (dma_info.cap == DMA_CYCLIC) {
+               dma_info.buf = pos;
+               prtd->params->ops->prepare(prtd->params->ch, &dma_info);
+               prtd->dma_loaded += limit;
+               return;
+       }
+
        while (prtd->dma_loaded < limit) {
                pr_debug("dma_loaded: %d\n", prtd->dma_loaded);