1 files changed, 31 insertions, 2 deletions

diff --git a/sound/soc/davinci/davinci-mcasp.c b/sound/soc/davinci/davinci-mcasp.c
index 818732de0f75..0aba39e7468d 100644
--- a/sound/soc/davinci/davinci-mcasp.c
+++ b/sound/soc/davinci/davinci-mcasp.c
@@ -304,6 +304,12 @@
 
 #define DAVINCI_MCASP_NUM_SERIALIZER    16
 
+/*
+ * Timeout value of 1 ms was chosen experimentally to account for the initial
+ * latency to have the first audio sample transferred to AFIFO by DMA
+ */
+#define MCASP_FIFO_FILL_TIMEOUT         1000
+
 static inline void mcasp_set_bits(void __iomem *reg, u32 val)
 {
         __raw_writel(__raw_readl(reg) | val, reg);
@@ -410,8 +416,11 @@ static void mcasp_start_tx(struct davinci_audio_dev *dev)
         mcasp_set_reg(dev->base + DAVINCI_MCASP_TXBUF_REG, 0);
 }
 
-static void davinci_mcasp_start(struct davinci_audio_dev *dev, int stream)
+static int davinci_mcasp_start(struct davinci_audio_dev *dev, int stream)
 {
+        int i = 0;
+        u32 val;
+
         if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
                 if (dev->txnumevt) {    /* enable FIFO */
                         switch (dev->version) {
@@ -427,6 +436,24 @@ static void davinci_mcasp_start(struct davinci_audio_dev *dev, int stream)
                                 mcasp_set_bits(dev->base +
                                         DAVINCI_MCASP_WFIFOCTL, FIFO_ENABLE);
                         }
+
+                        /*
+                         * Wait until DMA has loaded at least one sample into
+                         * AFIFO to ensure XRUN is not immediately hit
+                         * Implementation has to use udelay since it's executed
+                         * in atomic context (trigger() callback)
+                         */
+                        while (++i) {
+                                val = mcasp_get_reg(dev->base +
+                                                    MCASP_VER3_WFIFOSTS);
+                                if (val > 0)
+                                        break;
+
+                                if (i > MCASP_FIFO_FILL_TIMEOUT)
+                                        return -ETIMEDOUT;
+
+                                udelay(1);
+                        }
                 }
                 mcasp_start_tx(dev);
         } else {
@@ -447,6 +474,8 @@ static void davinci_mcasp_start(struct davinci_audio_dev *dev, int stream)
                 }
                 mcasp_start_rx(dev);
         }
+
+        return 0;
 }
 
 static void mcasp_stop_rx(struct davinci_audio_dev *dev)
@@ -967,7 +996,7 @@ static int davinci_mcasp_trigger(struct snd_pcm_substream *substream,
         case SNDRV_PCM_TRIGGER_RESUME:
         case SNDRV_PCM_TRIGGER_START:
         case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
-                davinci_mcasp_start(dev, substream->stream);
+                ret = davinci_mcasp_start(dev, substream->stream);
                 break;
 
         case SNDRV_PCM_TRIGGER_SUSPEND: