soundwire: intel: add prepare support in sdw dai driver

The existing code does not expose a prepare operation, which is very
much needed to deal with underflow and resume operations.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Rander Wang <rander.wang@linux.intel.com>
Acked-by: Sanyog Kale <sanyog.r.kale@intel.com>
Link: https://lore.kernel.org/r/20200215014740.27580-3-pierre-louis.bossart@linux.intel.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/soundwire/intel.c

@@ -699,6 +699,21 @@ static int intel_hw_params(struct snd_pcm_substream *substream,
 	return ret;
 }
 
+static int intel_prepare(struct snd_pcm_substream *substream,
+			 struct snd_soc_dai *dai)
+{
+	struct sdw_cdns_dma_data *dma;
+
+	dma = snd_soc_dai_get_dma_data(dai, substream);
+	if (!dma) {
+		dev_err(dai->dev, "failed to get dma data in %s",
+			__func__);
+		return -EIO;
+	}
+
+	return sdw_prepare_stream(dma->stream);
+}
+
 static int
 intel_hw_free(struct snd_pcm_substream *substream, struct snd_soc_dai *dai)
 {
@@ -745,6 +760,7 @@ static int intel_pdm_set_sdw_stream(struct snd_soc_dai *dai,
 
 static const struct snd_soc_dai_ops intel_pcm_dai_ops = {
 	.hw_params = intel_hw_params,
+	.prepare = intel_prepare,
 	.hw_free = intel_hw_free,
 	.shutdown = intel_shutdown,
 	.set_sdw_stream = intel_pcm_set_sdw_stream,
@@ -752,6 +768,7 @@ static const struct snd_soc_dai_ops intel_pcm_dai_ops = {
 
 static const struct snd_soc_dai_ops intel_pdm_dai_ops = {
 	.hw_params = intel_hw_params,
+	.prepare = intel_prepare,
 	.hw_free = intel_hw_free,
 	.shutdown = intel_shutdown,
 	.set_sdw_stream = intel_pdm_set_sdw_stream,