ASoC: SOF: Intel: hda: reserve host DMA channel for hostless streams

Due to the HW programming sequence requirement that the host
and link DMA channels need to be coupled/decoupled during pcm
hw_params, the host DMA channel corresponding to the link
DMA channel in use for hostless streams needs to be reserved.
This is achieved by adding a host_reserved flag in the
sof_intel_hda_stream structure which is checked when assigning
a host DMA channel.
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/intel/hda-dai.c

@@ -75,7 +75,7 @@ static struct hdac_ext_stream *
 
 		hda_stream = hstream_to_sof_hda_stream(hstream);
 
-		/* check if available */
+		/* check if link is available */
 		if (!hstream->link_locked) {
 			if (stream->opened) {
 				/*
@@ -89,6 +89,12 @@ static struct hdac_ext_stream *
 				}
 			} else {
 				res = hstream;
+
+				/*
+				 * This must be a hostless stream.
+				 * So reserve the host DMA channel.
+				 */
+				hda_stream->host_reserved = 1;
 				break;
 			}
 		}
@@ -368,6 +374,9 @@ static int hda_link_hw_free(struct snd_pcm_substream *substream,
 	snd_hdac_ext_stream_release(link_dev, HDAC_EXT_STREAM_TYPE_LINK);
 	link_dev->link_prepared = 0;
 
+	/* free the host DMA channel reserved by hostless streams */
+	hda_stream->host_reserved = 0;
+
 	return 0;
 }
 

sound/soc/sof/intel/hda-stream.c

@@ -155,6 +155,7 @@ struct hdac_ext_stream *
 hda_dsp_stream_get(struct snd_sof_dev *sdev, int direction)
 {
 	struct hdac_bus *bus = sof_to_bus(sdev);
+	struct sof_intel_hda_stream *hda_stream;
 	struct hdac_ext_stream *stream = NULL;
 	struct hdac_stream *s;
 
@@ -163,8 +164,15 @@ hda_dsp_stream_get(struct snd_sof_dev *sdev, int direction)
 	/* get an unused stream */
 	list_for_each_entry(s, &bus->stream_list, list) {
 		if (s->direction == direction && !s->opened) {
-			s->opened = true;
 			stream = stream_to_hdac_ext_stream(s);
+			hda_stream = container_of(stream,
+						  struct sof_intel_hda_stream,
+						  hda_stream);
+			/* check if the host DMA channel is reserved */
+			if (hda_stream->host_reserved)
+				continue;
+
+			s->opened = true;
 			break;
 		}
 	}

sound/soc/sof/intel/hda.h

@@ -413,6 +413,7 @@ struct sof_intel_hda_stream {
 	struct hdac_ext_stream hda_stream;
 	struct sof_intel_stream stream;
 	int hw_params_upon_resume; /* set up hw_params upon resume */
+	int host_reserved; /* reserve host DMA channel */
 };
 
 #define hstream_to_sof_hda_stream(hstream) \