[PATCH] ASoC: fsl: sai: Reduce underrun when stream starts

[Daniel Baluta]

From: Shengjiu Wang <shengjiu.w...@nxp.com>

Write initial words into SAI FIFO to reduce the underrun
error.

Signed-off-by: Shengjiu Wang <shengjiu.w...@nxp.com>
Signed-off-by: Daniel Baluta <daniel.bal...@nxp.com>
---
 sound/soc/fsl/fsl_sai.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index db9e0872f73d..99edbba4e8fa 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -503,7 +503,9 @@ static int fsl_sai_trigger(struct snd_pcm_substream 
*substream, int cmd,
 {
        struct fsl_sai *sai = snd_soc_dai_get_drvdata(cpu_dai);
        bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
+       unsigned int channels = substream->runtime->channels;
        u32 xcsr, count = 100;
+       int i;
 
        /*
         * Asynchronous mode: Clear SYNC for both Tx and Rx.
@@ -526,6 +528,11 @@ static int fsl_sai_trigger(struct snd_pcm_substream 
*substream, int cmd,
                regmap_update_bits(sai->regmap, FSL_SAI_xCSR(tx),
                                   FSL_SAI_CSR_FRDE, FSL_SAI_CSR_FRDE);
 
+               for (i = 0; tx && i < channels; i++)
+                       regmap_write(sai->regmap, FSL_SAI_TDR, 0x0);
+               if (tx)
+                       udelay(10);
+
                regmap_update_bits(sai->regmap, FSL_SAI_RCSR,
                                   FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE);
                regmap_update_bits(sai->regmap, FSL_SAI_TCSR,
-- 
2.17.1