ASoC: SOF: ipc4-topology: Change DeepBuffer from static to dynamic mode

Currently the DeepBuffer results static host DMA buffer and thus static
minimum ALSA period size which can be a limiting factor for user space.
DeepBuffer of static 100ms host DMA buffer can only be opened with at least
110ms ALSA period size, if for the same endpoint there is a need for
smaller (or larger) buffer then a new PCM device must be created with
different DeepBuffer configuration.
This does not scale in real life.

With Dynamic DeepBuffer the host DMA buffer size is calculated based on the
requested ALSA period size using the DEEP_BUFFER token as a maximum limit
for the host DMA buffer.

This way applications can use the same DeepBuffer enabled PCM for different
use cases and still benefit of the power saving of a bigger host DMA
buffer.

As an example, the DEEP_BUFFER in topology is set to 100ms (interpreted as
maximum size with this patch):
ALSA period:    8 -> dma buffer:   4 ms
ALSA period:   10 -> dma buffer:   6 ms
ALSA period:   16 -> dma buffer:  12 ms
ALSA period:   19 -> dma buffer:  15 ms
ALSA period:   20 -> dma buffer:  20 ms
ALSA period:   50 -> dma buffer:  50 ms
ALSA period:  100 -> dma buffer: 100 ms
ALSA period:  150 -> dma buffer: 100 ms
ALSA period: 2000 -> dma buffer: 100 ms

The Dynamic DeepBuffer will give applications the means to choose between
lower latency (small host DMA buffer) or higher power save (big host DMA
buffer) with higher latency on the same device with topology providing a
meaningful upper limit of the buffer size.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>

Author: ujfalusi

sound/soc/sof/ipc4-topology.c

@@ -670,22 +670,15 @@ static int sof_ipc4_widget_setup_pcm(struct snd_sof_widget *swidget)
 		goto free_available_fmt;
 
 	sps = &spcm->stream[dir];
-	sof_update_ipc_object(scomp, &sps->dsp_max_burst_size_in_ms,
-			      SOF_COPIER_DEEP_BUFFER_TOKENS,
-			      swidget->tuples,
-			      swidget->num_tuples, sizeof(u32), 1);
-
-	/* Set default DMA buffer size if it is not specified in topology */
-	if (!sps->dsp_max_burst_size_in_ms) {
+	if (dir == SNDRV_PCM_STREAM_PLAYBACK) {
 		struct snd_sof_widget *pipe_widget = swidget->spipe->pipe_widget;
 		struct sof_ipc4_pipeline *pipeline = pipe_widget->private;
 
-		if (dir == SNDRV_PCM_STREAM_PLAYBACK)
-			sps->dsp_max_burst_size_in_ms = pipeline->use_chain_dma ?
-				SOF_IPC4_CHAIN_DMA_BUFFER_SIZE : SOF_IPC4_MIN_DMA_BUFFER_SIZE;
-		else
-			/* Capture data is copied from DSP to host in 1ms bursts */
-			sps->dsp_max_burst_size_in_ms = 1;
+		sps->dsp_max_burst_size_in_ms = pipeline->use_chain_dma ?
+			SOF_IPC4_CHAIN_DMA_BUFFER_SIZE : SOF_IPC4_MIN_DMA_BUFFER_SIZE;
+	} else {
+		/* Capture data is copied from DSP to host in 1ms bursts */
+		sps->dsp_max_burst_size_in_ms = 1;
 	}
 
 skip_gtw_cfg:
@@ -2043,6 +2036,79 @@ static void sof_ipc4_host_config(struct snd_sof_dev *sdev, struct snd_sof_widget
 	copier_data->gtw_cfg.node_id |=	SOF_IPC4_NODE_INDEX(host_dma_id);
 }
 
+static void
+sof_ipc4_set_host_copier_dma_buffer_size(struct snd_sof_widget *swidget,
+					 unsigned int fe_period_bytes)
+{
+	unsigned int min_size, no_headroom_mark, fw_period_bytes;
+	struct snd_soc_component *scomp = swidget->scomp;
+	struct sof_ipc4_copier_data *copier_data;
+	struct sof_ipc4_copier *ipc4_copier;
+	unsigned int deep_buffer_dma_ms = 0;
+	u32 buffer_bytes;
+	int ret;
+
+	ipc4_copier = (struct sof_ipc4_copier *)swidget->private;
+	copier_data = &ipc4_copier->data;
+
+	if (swidget->id == snd_soc_dapm_aif_in)
+		fw_period_bytes = copier_data->base_config.ibs;
+	else
+		fw_period_bytes = copier_data->base_config.obs;
+
+	/*
+	 * Calculate the minimum size of the host copier DMA host buffer and the
+	 * cut-out watermark when no headroom is needed to be added between the
+	 * host copier buffer size and the ALSA period size
+	 */
+	min_size = SOF_IPC4_MIN_DMA_BUFFER_SIZE * fw_period_bytes;
+	no_headroom_mark = SOF_IPC4_NO_DMA_BUFFER_HEADROOM_MS * fw_period_bytes;
+
+	/* parse the deep buffer dma size */
+	ret = sof_update_ipc_object(scomp, &deep_buffer_dma_ms,
+				    SOF_COPIER_DEEP_BUFFER_TOKENS, swidget->tuples,
+				    swidget->num_tuples, sizeof(u32), 1);
+	if (ret) {
+		dev_dbg(scomp->dev,
+			"Failed to parse deep buffer dma size for %s\n",
+			swidget->widget->name);
+		buffer_bytes = min_size;
+		goto out;
+	}
+
+	/*
+	 * Non Deepbuffer and small ALSA periods must use the minimal host DMA
+	 * buffer size in firmware.
+	 * Note: smaller than 2x the minimum host DMA buffer size for ALSA
+	 * period is not allowed and should be protected by platform code with
+	 * constraint.
+	 *
+	 * Add headroom the between host copier DMA buffer size and the ALSA
+	 * period size if the ALSA period is less than 
+	 * SOF_IPC4_NO_DMA_BUFFER_HEADROOM_MS, otherwise equal the host copier
+	 * DMA buffer size to ALSA period size, capped at the maximum DeepBuffer
+	 * depth specified in topology
+	 */
+	if (deep_buffer_dma_ms <= SOF_IPC4_MIN_DMA_BUFFER_SIZE ||
+	    fe_period_bytes < (min_size * 2))
+		buffer_bytes = min_size;
+	else if (fe_period_bytes < no_headroom_mark)
+		buffer_bytes = fe_period_bytes - min_size;
+	else
+		buffer_bytes = min(deep_buffer_dma_ms * fw_period_bytes,
+				   fe_period_bytes);
+
+out:
+	dev_dbg(scomp->dev,
+		"%s, dma buffer%s: %u ms (max: %u) / %u bytes, ALSA period: %u / %u\n",
+		swidget->widget->name, deep_buffer_dma_ms ? " (using Deep Buffer)" : "",
+		buffer_bytes / fw_period_bytes,
+		deep_buffer_dma_ms ? deep_buffer_dma_ms : SOF_IPC4_MIN_DMA_BUFFER_SIZE,
+		buffer_bytes, fe_period_bytes / fw_period_bytes, fe_period_bytes);
+
+	copier_data->gtw_cfg.dma_buffer_size = buffer_bytes;
+}
+
 static int
 sof_ipc4_prepare_copier_module(struct snd_sof_widget *swidget,
 			       struct snd_pcm_hw_params *fe_params,
@@ -2064,7 +2130,6 @@ sof_ipc4_prepare_copier_module(struct snd_sof_widget *swidget,
 	u32 **data;
 	int ipc_size, ret, out_ref_valid_bits;
 	u32 out_ref_rate, out_ref_channels, out_ref_type;
-	u32 deep_buffer_dma_ms = 0;
 	bool single_output_bitdepth;
 	int i;
 
@@ -2082,16 +2147,6 @@ sof_ipc4_prepare_copier_module(struct snd_sof_widget *swidget,
 			str_yes_no(pipeline->use_chain_dma),
 			platform_params->stream_tag);
 
-		/* parse the deep buffer dma size */
-		ret = sof_update_ipc_object(scomp, &deep_buffer_dma_ms,
-					    SOF_COPIER_DEEP_BUFFER_TOKENS, swidget->tuples,
-					    swidget->num_tuples, sizeof(u32), 1);
-		if (ret) {
-			dev_err(scomp->dev, "Failed to parse deep buffer dma size for %s\n",
-				swidget->widget->name);
-			return ret;
-		}
-
 		ipc4_copier = (struct sof_ipc4_copier *)swidget->private;
 		gtw_attr = ipc4_copier->gtw_attr;
 		copier_data = &ipc4_copier->data;
@@ -2426,34 +2481,19 @@ sof_ipc4_prepare_copier_module(struct snd_sof_widget *swidget,
 	 * in topology.
 	 */
 	switch (swidget->id) {
+	case snd_soc_dapm_aif_in:
+	case snd_soc_dapm_aif_out:
+		sof_ipc4_set_host_copier_dma_buffer_size(swidget,
+							 params_period_bytes(fe_params));
+		break;
 	case snd_soc_dapm_dai_in:
 		copier_data->gtw_cfg.dma_buffer_size =
 			SOF_IPC4_MIN_DMA_BUFFER_SIZE * copier_data->base_config.ibs;
 		break;
-	case snd_soc_dapm_aif_in:
-		copier_data->gtw_cfg.dma_buffer_size =
-			max((u32)SOF_IPC4_MIN_DMA_BUFFER_SIZE, deep_buffer_dma_ms) *
-				copier_data->base_config.ibs;
-		dev_dbg(sdev->dev, "copier %s, dma buffer%s: %u ms (%u bytes)",
-			swidget->widget->name,
-			deep_buffer_dma_ms ? " (using Deep Buffer)" : "",
-			max((u32)SOF_IPC4_MIN_DMA_BUFFER_SIZE, deep_buffer_dma_ms),
-			copier_data->gtw_cfg.dma_buffer_size);
-		break;
 	case snd_soc_dapm_dai_out:
 		copier_data->gtw_cfg.dma_buffer_size =
 			SOF_IPC4_MIN_DMA_BUFFER_SIZE * copier_data->base_config.obs;
 		break;
-	case snd_soc_dapm_aif_out:
-		copier_data->gtw_cfg.dma_buffer_size =
-			max((u32)SOF_IPC4_MIN_DMA_BUFFER_SIZE, deep_buffer_dma_ms) *
-				copier_data->base_config.obs;
-		dev_dbg(sdev->dev, "copier %s, dma buffer%s: %u ms (%u bytes)",
-			swidget->widget->name,
-			deep_buffer_dma_ms ? " (using Deep Buffer)" : "",
-			max((u32)SOF_IPC4_MIN_DMA_BUFFER_SIZE, deep_buffer_dma_ms),
-			copier_data->gtw_cfg.dma_buffer_size);
-		break;
 	default:
 		break;
 	}

sound/soc/sof/ipc4-topology.h

@@ -76,6 +76,17 @@
 /* ChainDMA in fw uses 5ms DMA buffer */
 #define SOF_IPC4_CHAIN_DMA_BUFFER_SIZE	5
 
+/*
+ * When the host DMA buffer size is larger than 8ms, the firmware switches from
+ * a constant fill mode to burst mode, keeping a 4ms threshold to trigger a
+ * transfer of approximately host DMA buffer size - 4ms after the initial burst
+ * to fill the entire buffer.
+ * To simplify the logic, above 20ms ALSA period size use the same size for host
+ * DMA buffer, while if the ALSA period size is smaller than 20ms, then use a
+ * headroom between host DMA buffer and ALSA period size.
+ */
+#define SOF_IPC4_NO_DMA_BUFFER_HEADROOM_MS	20
+
 /*
  * The base of multi-gateways. Multi-gateways addressing starts from
  * ALH_MULTI_GTW_BASE and there are ALH_MULTI_GTW_COUNT multi-sources