Revert "ASoC: SOF: ipc4/Intel: Rename dsp_max_burst_size_in_ms to dsp_min_burst_size_in_ms"

This reverts commit a3cb9cc.

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

Author: ujfalusi

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

@@ -29,6 +29,8 @@
 #define SDnFMT_BITS(x)	((x) << 4)
 #define SDnFMT_CHAN(x)	((x) << 0)
 
+#define HDA_MAX_PERIOD_TIME_HEADROOM	10
+
 static bool hda_always_enable_dmi_l1;
 module_param_named(always_enable_dmi_l1, hda_always_enable_dmi_l1, bool, 0444);
 MODULE_PARM_DESC(always_enable_dmi_l1, "SOF HDA always enable DMI l1");
@@ -295,19 +297,35 @@ int hda_dsp_pcm_open(struct snd_sof_dev *sdev,
 					     SNDRV_PCM_FMTBIT_S16 | SNDRV_PCM_FMTBIT_S32);
 
 	/*
-	 * The dsp_min_burst_size_in_ms is the length of the minimum burst size
+	 * The dsp_max_burst_size_in_ms is the length of the maximum burst size
 	 * of the host DMA in the ALSA buffer.
 	 *
-	 * Set a constraint to period time min to be at least twice as long as
-	 * the minimum burst size to avoid DMA overruns
+	 * On playback start the DMA will transfer dsp_max_burst_size_in_ms
+	 * amount of data in one initial burst to fill up the host DMA buffer.
+	 * Consequent DMA burst sizes are shorter and their length can vary.
+	 * To avoid immediate xrun by the initial burst we need to place
+	 * constraint on the period size (via PERIOD_TIME) to cover the size of
+	 * the host buffer.
+	 * We need to add headroom of max 10ms as the firmware needs time to
+	 * settle to the 1ms pacing and initially it can run faster for few
+	 * internal periods.
+	 *
+	 * On capture the DMA will transfer 1ms chunks.
 	 */
-	if (spcm->stream[direction].dsp_min_burst_size_in_ms) {
-		unsigned int burst_time = spcm->stream[direction].dsp_min_burst_size_in_ms;
+	if (spcm->stream[direction].dsp_max_burst_size_in_ms) {
+		unsigned int period_time = spcm->stream[direction].dsp_max_burst_size_in_ms;
+
+		/*
+		 * add headroom over the maximum burst size to cover the time
+		 * needed for the DMA pace to settle.
+		 * Limit the headroom time to HDA_MAX_PERIOD_TIME_HEADROOM
+		 */
+		period_time += min(period_time, HDA_MAX_PERIOD_TIME_HEADROOM);
 
 		snd_pcm_hw_constraint_minmax(substream->runtime,
-					     SNDRV_PCM_HW_PARAM_PERIOD_TIME,
-					     burst_time * USEC_PER_MSEC * 2,
-					     UINT_MAX);
+			SNDRV_PCM_HW_PARAM_PERIOD_TIME,
+			period_time * USEC_PER_MSEC,
+			UINT_MAX);
 	}
 
 	/* binding pcm substream to hda stream */

sound/soc/sof/ipc4-topology.c

@@ -692,11 +692,11 @@ static int sof_ipc4_widget_setup_pcm(struct snd_sof_widget *swidget)
 		struct snd_sof_widget *pipe_widget = swidget->spipe->pipe_widget;
 		struct sof_ipc4_pipeline *pipeline = pipe_widget->private;
 
-		sps->dsp_min_burst_size_in_ms = pipeline->use_chain_dma ?
+		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_min_burst_size_in_ms = 1;
+		sps->dsp_max_burst_size_in_ms = 1;
 	}
 
 skip_gtw_cfg:

sound/soc/sof/sof-audio.h

@@ -336,7 +336,7 @@ struct snd_sof_pcm_stream {
 	struct snd_soc_dapm_widget_list *list; /* list of connected DAPM widgets */
 	bool d0i3_compatible; /* DSP can be in D0I3 when this pcm is opened */
 	bool pause_supported; /* PCM device supports PAUSE operation */
-	unsigned int dsp_min_burst_size_in_ms; /* The minimum size of the host DMA burst in ms */
+	unsigned int dsp_max_burst_size_in_ms; /* The maximum size of the host DMA burst in ms */
 	/*
 	 * flag to indicate that the DSP pipelines should be kept
 	 * active or not while suspending the stream