ASoC: SOF: Intel: hda: reserve link/host DMA channels with same ID

The sequence of PCM ops upon starting a PCM stream in SOF is as
follows (Showing only the hw_params and trigger ops):

Host hw_params -> Link hw_params -> Host START -> Link START

For HDA streams, the host DMA channel would be assigned during
host hw_params and the corresponding link DMA channel would be
assigned in link hw_params.

But for non-HDA streams such as I2S, DMIC and trace DMA,
only the host DMA is used. Therefore, the link DMA channel
corresponding to the host DMA channel will not be
assigned as there is no link hw_params as shown in the sequence above
The recommended HDA HW programming sequence requires that the host DMA
channel and link DMA channel with the same ID be coupled before DMA
format setting and decoupled right after. This would lead to issues
with concurrent usecases when the host DMA and link DMA channels for
a HDA stream do not match. Therefore, when the link DMA channel
corresponding to the host DMA channel for non-HDA streams
must be reserved by setting link_locked in the host START
trigger op to prevent it from being assigned to another stream.

Similar logic applies to hostless streams, where the link DMA
is in use but the host DMA is not in use. The host DMA
channel corresponding to the link DMA channel must be reserved
to prevent it from being assigned to another stream.

Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>

Author: ranj063

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

@@ -145,6 +145,8 @@ static int hda_link_pcm_trigger(struct snd_pcm_substream *substream,
 {
 	struct hdac_ext_stream *link_dev =
 				snd_soc_dai_get_dma_data(dai, substream);
+	struct hdac_stream stream = link_dev->hstream;
+
 	int ret;
 
 	dev_dbg(dai->dev, "In %s cmd=%d\n", __func__, cmd);
@@ -161,11 +163,25 @@ static int hda_link_pcm_trigger(struct snd_pcm_substream *substream,
 		/* fallthrough */
 	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+		/*
+		 * The recommended HDA HW programming sequence requires host
+		 * DMA and link DMA with the same IDs to be coupled before
+		 * setting the DMA format. For PCM streams, the host
+		 * DMA channel corresponding to the link DMA channel would
+		 * be assigned. But hostless pipelines (Ex: tone) do not use
+		 * host DMA. So, the host DMA channel with the same ID as the
+		 * link DMA must be reserved to prevent it from being assigned
+		 * to another stream.
+		 */
+		stream.opened = 1;
 		snd_hdac_ext_link_stream_start(link_dev);
 		break;
-	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_STOP:
+		stream.opened = 0;
+
+		/* fallthrough */
+	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 		snd_hdac_ext_link_stream_clear(link_dev);
 		break;
 	default:

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

@@ -213,8 +213,23 @@ int hda_dsp_stream_trigger(struct snd_sof_dev *sdev,
 	/* cmd must be for audio stream */
 	switch (cmd) {
 	case SNDRV_PCM_TRIGGER_RESUME:
-	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
 	case SNDRV_PCM_TRIGGER_START:
+		/*
+		 * The recommended HDA HW programming sequence requires host
+		 * DMA and link DMA with the same IDs to be coupled before
+		 * setting the DMA format. Both HDA and non-HDA streams utilize
+		 * host DMA but non-HDA streams (ex: I2S, DMIC etc) do not use
+		 * link DMA. In the case of HDA streams, the link hw_params
+		 * ioctl would handle handle locking the link DMA channel in
+		 * use. But for non-HDA streams, since link DMA is not used,
+		 * the link DMA channel with the same ID as the host DMA must
+		 * be reserved to prevent it from being assigned to another
+		 * stream.
+		 */
+		stream->link_locked = 1;
+
+		/* fallthrough */
+	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
 		snd_sof_dsp_update_bits(sdev, HDA_DSP_HDA_BAR, SOF_HDA_INTCTL,
 					1 << hstream->index,
 					1 << hstream->index);
@@ -229,8 +244,12 @@ int hda_dsp_stream_trigger(struct snd_sof_dev *sdev,
 		hstream->running = true;
 		break;
 	case SNDRV_PCM_TRIGGER_SUSPEND:
-	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 	case SNDRV_PCM_TRIGGER_STOP:
+		/* unlock link DMA channel */
+		stream->link_locked = 0;
+
+		/* fallthrough */
+	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 		snd_sof_dsp_update_bits(sdev, HDA_DSP_HDA_BAR,
 					sd_offset,
 					SOF_HDA_SD_CTL_DMA_START |
@@ -241,6 +260,7 @@ int hda_dsp_stream_trigger(struct snd_sof_dev *sdev,
 				  SOF_HDA_CL_DMA_SD_INT_MASK);
 
 		hstream->running = false;
+
 		snd_sof_dsp_update_bits(sdev, HDA_DSP_HDA_BAR, SOF_HDA_INTCTL,
 					1 << hstream->index, 0x0);
 		break;

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

@@ -51,6 +51,15 @@ int hda_dsp_trace_init(struct snd_sof_dev *sdev, u32 *stream_tag)
 		return -ENODEV;
 	}
 
+	/*
+	 * The recommended HDA HW programming sequence requires host DMA and
+	 * link DMA with the same IDs to be coupled before setting the
+	 * DMA format. Therefore, even though trace utilizes only host DMA
+	 * in decoupled mode, the link DMA channel with the same ID must be
+	 * reserved to avoid it being assigned to another stream.
+	 */
+	hda->dtrace_stream->link_locked = 1;
+
 	*stream_tag = hda->dtrace_stream->hstream.stream_tag;
 
 	/*
@@ -78,6 +87,7 @@ int hda_dsp_trace_release(struct snd_sof_dev *sdev)
 		hda_dsp_stream_put(sdev,
 				   SNDRV_PCM_STREAM_CAPTURE,
 				   hstream->stream_tag);
+		hda->dtrace_stream->link_locked = 0;
 		hda->dtrace_stream = NULL;
 		return 0;
 	}