The dma channel has been requested by Back-End cpu dai driver already.
If fsl_asrc_dma requests dma chan with same dma:tx symlink, then
there will be below warning with SDMA.

[   48.174236] fsl-esai-dai 2024000.esai: Cannot create DMA dma:tx symlink

or with EDMA the request operation will fail for EDMA channel
can only be requested once.

So If we can reuse the dma channel of Back-End, then the issue can be
fixed.

In order to get the dma channel which is already requested in Back-End.
we use the exported two functions (snd_soc_lookup_component_nolocked
and soc_component_to_pcm). If we can get the dma channel, then reuse it,
if can't, then request a new one.

Signed-off-by: Shengjiu Wang <shengjiu.w...@nxp.com>
---
 sound/soc/fsl/fsl_asrc_common.h |  2 ++
 sound/soc/fsl/fsl_asrc_dma.c    | 52 +++++++++++++++++++++++++--------
 2 files changed, 42 insertions(+), 12 deletions(-)

diff --git a/sound/soc/fsl/fsl_asrc_common.h b/sound/soc/fsl/fsl_asrc_common.h
index 77665b15c8db..09512bc79b80 100644
--- a/sound/soc/fsl/fsl_asrc_common.h
+++ b/sound/soc/fsl/fsl_asrc_common.h
@@ -32,6 +32,7 @@ enum asrc_pair_index {
  * @dma_chan: inputer and output DMA channels
  * @dma_data: private dma data
  * @pos: hardware pointer position
+ * @req_dma_chan_dev_to_dev: flag for release dev_to_dev chan
  * @private: pair private area
  */
 struct fsl_asrc_pair {
@@ -45,6 +46,7 @@ struct fsl_asrc_pair {
        struct dma_chan *dma_chan[2];
        struct imx_dma_data dma_data;
        unsigned int pos;
+       bool req_dma_chan_dev_to_dev;
 
        void *private;
 };
diff --git a/sound/soc/fsl/fsl_asrc_dma.c b/sound/soc/fsl/fsl_asrc_dma.c
index d6a3fc5f87e5..5ecb77d466d3 100644
--- a/sound/soc/fsl/fsl_asrc_dma.c
+++ b/sound/soc/fsl/fsl_asrc_dma.c
@@ -133,6 +133,7 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component 
*component,
        bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
        struct snd_dmaengine_dai_dma_data *dma_params_fe = NULL;
        struct snd_dmaengine_dai_dma_data *dma_params_be = NULL;
+       struct dma_chan *tmp_chan = NULL, *tmp_chan_new = NULL;
        struct snd_pcm_runtime *runtime = substream->runtime;
        struct fsl_asrc_pair *pair = runtime->private_data;
        struct fsl_asrc *asrc = pair->asrc;
@@ -142,7 +143,6 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component 
*component,
        int stream = substream->stream;
        struct imx_dma_data *tmp_data;
        struct snd_soc_dpcm *dpcm;
-       struct dma_chan *tmp_chan;
        struct device *dev_be;
        u8 dir = tx ? OUT : IN;
        dma_cap_mask_t mask;
@@ -152,6 +152,7 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component 
*component,
        for_each_dpcm_be(rtd, stream, dpcm) {
                struct snd_soc_pcm_runtime *be = dpcm->be;
                struct snd_pcm_substream *substream_be;
+               struct snd_soc_component *component_be;
                struct snd_soc_dai *dai = asoc_rtd_to_cpu(be, 0);
 
                if (dpcm->fe != rtd)
@@ -160,6 +161,9 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component 
*component,
                substream_be = snd_soc_dpcm_get_substream(be, stream);
                dma_params_be = snd_soc_dai_get_dma_data(dai, substream_be);
                dev_be = dai->dev;
+               component_be = snd_soc_lookup_component_nolocked(dev_be, 
SND_DMAENGINE_PCM_DRV_NAME);
+               if (component_be)
+                       tmp_chan = 
soc_component_to_pcm(component_be)->chan[substream->stream];
                break;
        }
 
@@ -205,10 +209,14 @@ static int fsl_asrc_dma_hw_params(struct 
snd_soc_component *component,
         */
        if (!asrc->use_edma) {
                /* Get DMA request of Back-End */
-               tmp_chan = dma_request_slave_channel(dev_be, tx ? "tx" : "rx");
+               if (!tmp_chan) {
+                       tmp_chan_new = dma_request_slave_channel(dev_be, tx ? 
"tx" : "rx");
+                       tmp_chan = tmp_chan_new;
+               }
                tmp_data = tmp_chan->private;
                pair->dma_data.dma_request = tmp_data->dma_request;
-               dma_release_channel(tmp_chan);
+               if (tmp_chan_new)
+                       dma_release_channel(tmp_chan_new);
 
                /* Get DMA request of Front-End */
                tmp_chan = asrc->get_dma_channel(pair, dir);
@@ -220,9 +228,26 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component 
*component,
 
                pair->dma_chan[dir] =
                        dma_request_channel(mask, filter, &pair->dma_data);
+               pair->req_dma_chan_dev_to_dev = true;
        } else {
-               pair->dma_chan[dir] =
-                       asrc->get_dma_channel(pair, dir);
+               /*
+                * With EDMA, there is two dma channels can be used for p2p,
+                * one is from ASRC, one is from another peripheral
+                * (ESAI or SAI). Previously we select the dma channel of ASRC,
+                * but find an issue for ideal ratio case, there is no control
+                * for data copy speed, the speed is faster than sample
+                * frequency.
+                *
+                * So we switch to use dma channel of peripheral (ESAI or SAI),
+                * that copy speed of DMA is controlled by data consumption
+                * speed in the peripheral FIFO.
+                */
+               pair->req_dma_chan_dev_to_dev = false;
+               pair->dma_chan[dir] = tmp_chan;
+               if (!pair->dma_chan[dir]) {
+                       pair->dma_chan[dir] = dma_request_slave_channel(dev_be, 
tx ? "tx" : "rx");
+                       pair->req_dma_chan_dev_to_dev = true;
+               }
        }
 
        if (!pair->dma_chan[dir]) {
@@ -261,7 +286,8 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component 
*component,
        ret = dmaengine_slave_config(pair->dma_chan[dir], &config_be);
        if (ret) {
                dev_err(dev, "failed to config DMA channel for Back-End\n");
-               dma_release_channel(pair->dma_chan[dir]);
+               if (pair->req_dma_chan_dev_to_dev)
+                       dma_release_channel(pair->dma_chan[dir]);
                return ret;
        }
 
@@ -273,19 +299,21 @@ static int fsl_asrc_dma_hw_params(struct 
snd_soc_component *component,
 static int fsl_asrc_dma_hw_free(struct snd_soc_component *component,
                                struct snd_pcm_substream *substream)
 {
+       bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
        struct snd_pcm_runtime *runtime = substream->runtime;
        struct fsl_asrc_pair *pair = runtime->private_data;
+       u8 dir = tx ? OUT : IN;
 
        snd_pcm_set_runtime_buffer(substream, NULL);
 
-       if (pair->dma_chan[IN])
-               dma_release_channel(pair->dma_chan[IN]);
+       if (pair->dma_chan[!dir])
+               dma_release_channel(pair->dma_chan[!dir]);
 
-       if (pair->dma_chan[OUT])
-               dma_release_channel(pair->dma_chan[OUT]);
+       if (pair->dma_chan[dir] && pair->req_dma_chan_dev_to_dev)
+               dma_release_channel(pair->dma_chan[dir]);
 
-       pair->dma_chan[IN] = NULL;
-       pair->dma_chan[OUT] = NULL;
+       pair->dma_chan[!dir] = NULL;
+       pair->dma_chan[dir] = NULL;
 
        return 0;
 }
-- 
2.21.0

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