[PATCH 2/2] ASoC: SOF: Intel: add hw specific PCM constraints

[Kai Vehmanen]

Part of PCM constraints are set based on DSP topology, but rest
should be set based on hardware capabilities. Add PCM constraints
for Intel platforms:

- Add constraint for the period count to be integer. This avoids
  wrap-arounds of the DMA circular buffer in middle of a period.

- Align period size to dword/32bit as per HDA spec.

Both constraints are aligned with current implementation in snd-hda-intel
driver.

Signed-off-by: Kai Vehmanen <kai.vehmanen at linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan at linux.intel.com>
---
 sound/soc/sof/intel/hda-pcm.c   | 7 +++++++
 sound/soc/sof/intel/intel-ipc.c | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/sound/soc/sof/intel/hda-pcm.c b/sound/soc/sof/intel/hda-pcm.c
index b527d5958ae5..5d35bb18660a 100644
--- a/sound/soc/sof/intel/hda-pcm.c
+++ b/sound/soc/sof/intel/hda-pcm.c
@@ -225,6 +225,13 @@ int hda_dsp_pcm_open(struct snd_sof_dev *sdev,
 		return -ENODEV;
 	}
 
+	/* minimum as per HDA spec */
+	snd_pcm_hw_constraint_step(substream->runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_BYTES, 4);
+
+	/* avoid circular buffer wrap in middle of period */
+	snd_pcm_hw_constraint_integer(substream->runtime,
+				      SNDRV_PCM_HW_PARAM_PERIODS);
+
 	/* binding pcm substream to hda stream */
 	substream->runtime->private_data = &dsp_stream->hstream;
 	return 0;
diff --git a/sound/soc/sof/intel/intel-ipc.c b/sound/soc/sof/intel/intel-ipc.c
index 310f9168c124..de66f8a82a07 100644
--- a/sound/soc/sof/intel/intel-ipc.c
+++ b/sound/soc/sof/intel/intel-ipc.c
@@ -73,6 +73,13 @@ int intel_pcm_open(struct snd_sof_dev *sdev,
 	/* binding pcm substream to hda stream */
 	substream->runtime->private_data = stream;
 
+	/* align to DMA minimum transfer size */
+	snd_pcm_hw_constraint_step(substream->runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_BYTES, 4);
+
+	/* avoid circular buffer wrap in middle of period */
+	snd_pcm_hw_constraint_integer(substream->runtime,
+				      SNDRV_PCM_HW_PARAM_PERIODS);
+
 	return 0;
 }
 EXPORT_SYMBOL_NS(intel_pcm_open, SND_SOC_SOF_INTEL_HIFI_EP_IPC);
-- 
2.28.0