ASoC: fsl_asrc_dma: Fix warning "Cannot create DMA dma:tx symlink"

The issue log is:

[   48.021506] CPU: 0 PID: 664 Comm: aplay Not tainted 5.7.0-rc1-13120-g12b434cbbea0 torvalds#343
[   48.031063] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
[   48.037638] [<c0110dd8>] (unwind_backtrace) from [<c010b8ec>] (show_stack+0x10/0x14)
[   48.045413] [<c010b8ec>] (show_stack) from [<c0557fc0>] (dump_stack+0xe4/0x118)
[   48.052757] [<c0557fc0>] (dump_stack) from [<c032aeb4>] (sysfs_warn_dup+0x50/0x64)
[   48.060357] [<c032aeb4>] (sysfs_warn_dup) from [<c032b1a8>] (sysfs_do_create_link_sd+0xc8/0xd4)
[   48.069086] [<c032b1a8>] (sysfs_do_create_link_sd) from [<c05dc668>] (dma_request_chan+0xb0/0x210)
[   48.078068] [<c05dc668>] (dma_request_chan) from [<c05dc7d0>] (dma_request_slave_channel+0x8/0x14)
[   48.087060] [<c05dc7d0>] (dma_request_slave_channel) from [<c09d5cd4>] (fsl_asrc_dma_hw_params+0x1dc/0x434)
[   48.096831] [<c09d5cd4>] (fsl_asrc_dma_hw_params) from [<c09c143c>] (soc_pcm_hw_params+0x4b0/0x650)
[   48.105903] [<c09c143c>] (soc_pcm_hw_params) from [<c09c36a8>] (dpcm_fe_dai_hw_params+0x70/0xe4)
[   48.114715] [<c09c36a8>] (dpcm_fe_dai_hw_params) from [<c099b274>] (snd_pcm_hw_params+0x158/0x418)
[   48.123701] [<c099b274>] (snd_pcm_hw_params) from [<c099c5a0>] (snd_pcm_ioctl+0x734/0x183c)
[   48.132079] [<c099c5a0>] (snd_pcm_ioctl) from [<c029ff94>] (ksys_ioctl+0x2ac/0xb98)
[   48.139765] [<c029ff94>] (ksys_ioctl) from [<c0100080>] (ret_fast_syscall+0x0/0x28)
[   48.147440] Exception stack(0xed3c5fa8 to 0xed3c5ff0)
[   48.152515] 5fa0:                   bec28670 00e92870 00000004 c25c4111 bec28670 0002000f
[   48.160716] 5fc0: bec28670 00e92870 00e92820 00000036 0000bb80 00000000 0002c2f8 00000003
[   48.168913] 5fe0: b6f4d3fc bec2853c b6ee7655 b6e22cf8
[   48.174236] fsl-esai-dai 2024000.esai: Cannot create DMA dma:tx symlink

The dma channel is already requested by Back-End cpu dai driver,
if fsl_asrc_dma requests dma chan with same dma:tx symlink, then
this warning comes out.

The warning is added by
commit 71723a9 ("dmaengine: Create symlinks between DMA channels and slaves")
commit bad8356 ("dmaengine: Cleanups for the slave <-> channel symlink support")

As the dma channel is requested by Back-End, we need to reuse the channel
and avoid to request a new one, then the issue can be fixed.

In order to get the dma channel which is already requested in Back-End.
we export 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.wang@nxp.com>

include/sound/dmaengine_pcm.h

@@ -161,4 +161,15 @@ int snd_dmaengine_pcm_prepare_slave_config(struct snd_pcm_substream *substream,
 
 #define SND_DMAENGINE_PCM_DRV_NAME "snd_dmaengine_pcm"
 
+struct dmaengine_pcm {
+	struct dma_chan *chan[SNDRV_PCM_STREAM_LAST + 1];
+	const struct snd_dmaengine_pcm_config *config;
+	struct snd_soc_component component;
+	unsigned int flags;
+};
+
+static inline struct dmaengine_pcm *soc_component_to_pcm(struct snd_soc_component *p)
+{
+	return container_of(p, struct dmaengine_pcm, component);
+}
 #endif

include/sound/soc.h

@@ -444,6 +444,8 @@ int devm_snd_soc_register_component(struct device *dev,
 			 const struct snd_soc_component_driver *component_driver,
 			 struct snd_soc_dai_driver *dai_drv, int num_dai);
 void snd_soc_unregister_component(struct device *dev);
+struct snd_soc_component *snd_soc_lookup_component_nolocked(struct device *dev,
+							    const char *driver_name);
 struct snd_soc_component *snd_soc_lookup_component(struct device *dev,
 						   const char *driver_name);
 

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;
 };

sound/soc/fsl/fsl_asrc_dma.c

@@ -135,14 +135,15 @@ static int fsl_asrc_dma_hw_params(struct snd_soc_component *component,
 	struct snd_dmaengine_dai_dma_data *dma_params_be = NULL;
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct fsl_asrc_pair *pair = runtime->private_data;
+	struct snd_soc_component *component_be = NULL;
 	struct fsl_asrc *asrc = pair->asrc;
 	struct dma_slave_config config_fe, config_be;
 	enum asrc_pair_index index = pair->index;
 	struct device *dev = component->dev;
 	int stream = substream->stream;
 	struct imx_dma_data *tmp_data;
 	struct snd_soc_dpcm *dpcm;
-	struct dma_chan *tmp_chan;
+	struct dma_chan *tmp_chan = NULL, *tmp_chan_new = NULL;
 	struct device *dev_be;
 	u8 dir = tx ? OUT : IN;
 	dma_cap_mask_t mask;
@@ -160,6 +161,7 @@ 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);
 		break;
 	}
 
@@ -205,10 +207,16 @@ 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 (component_be)
+			tmp_chan = soc_component_to_pcm(component_be)->chan[substream->stream];
+		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 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;
+		if (component_be)
+			pair->dma_chan[dir] = soc_component_to_pcm(component_be)->chan[substream->stream];;
+		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]) {
@@ -273,19 +298,21 @@ 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;
 }

sound/soc/soc-core.c

@@ -310,7 +310,7 @@ struct snd_soc_component *snd_soc_rtdcom_lookup(struct snd_soc_pcm_runtime *rtd,
 }
 EXPORT_SYMBOL_GPL(snd_soc_rtdcom_lookup);
 
-static struct snd_soc_component
+struct snd_soc_component
 *snd_soc_lookup_component_nolocked(struct device *dev, const char *driver_name)
 {
 	struct snd_soc_component *component;
@@ -329,6 +329,7 @@ static struct snd_soc_component
 
 	return found_component;
 }
+EXPORT_SYMBOL_GPL(snd_soc_lookup_component_nolocked);
 
 struct snd_soc_component *snd_soc_lookup_component(struct device *dev,
 						   const char *driver_name)

sound/soc/soc-generic-dmaengine-pcm.c

@@ -21,18 +21,6 @@
  */
 #define SND_DMAENGINE_PCM_FLAG_NO_RESIDUE BIT(31)
 
-struct dmaengine_pcm {
-	struct dma_chan *chan[SNDRV_PCM_STREAM_LAST + 1];
-	const struct snd_dmaengine_pcm_config *config;
-	struct snd_soc_component component;
-	unsigned int flags;
-};
-
-static struct dmaengine_pcm *soc_component_to_pcm(struct snd_soc_component *p)
-{
-	return container_of(p, struct dmaengine_pcm, component);
-}
-
 static struct device *dmaengine_dma_dev(struct dmaengine_pcm *pcm,
 	struct snd_pcm_substream *substream)
 {