ASoC: atmel_ssc_dai: move set dma data to startup callback

move set dma data to startup callback function, if the set dma
data exist in hw_params callback, so the dma data only usable when
call hw_params, if want use it before hw_params callback, it will
cause NULL pointer access oops

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/atmel/atmel_ssc_dai.c

@@ -196,15 +196,27 @@ static int atmel_ssc_startup(struct snd_pcm_substream *substream,
 			     struct snd_soc_dai *dai)
 {
 	struct atmel_ssc_info *ssc_p = &ssc_info[dai->id];
-	int dir_mask;
+	struct atmel_pcm_dma_params *dma_params;
+	int dir, dir_mask;
 
 	pr_debug("atmel_ssc_startup: SSC_SR=0x%u\n",
 		ssc_readl(ssc_p->ssc->regs, SR));
 
-	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
+		dir = 0;
 		dir_mask = SSC_DIR_MASK_PLAYBACK;
-	else
+	} else {
+		dir = 1;
 		dir_mask = SSC_DIR_MASK_CAPTURE;
+	}
+
+	dma_params = &ssc_dma_params[dai->id][dir];
+	dma_params->ssc = ssc_p->ssc;
+	dma_params->substream = substream;
+
+	ssc_p->dma_params[dir] = dma_params;
+
+	snd_soc_dai_set_dma_data(dai, substream, dma_params);
 
 	spin_lock_irq(&ssc_p->lock);
 	if (ssc_p->dir_mask & dir_mask) {
@@ -325,7 +337,6 @@ static int atmel_ssc_hw_params(struct snd_pcm_substream *substream,
 	struct snd_pcm_hw_params *params,
 	struct snd_soc_dai *dai)
 {
-	struct snd_soc_pcm_runtime *rtd = snd_pcm_substream_chip(substream);
 	int id = dai->id;
 	struct atmel_ssc_info *ssc_p = &ssc_info[id];
 	struct atmel_pcm_dma_params *dma_params;
@@ -344,19 +355,7 @@ static int atmel_ssc_hw_params(struct snd_pcm_substream *substream,
 	else
 		dir = 1;
 
-	dma_params = &ssc_dma_params[id][dir];
-	dma_params->ssc = ssc_p->ssc;
-	dma_params->substream = substream;
-
-	ssc_p->dma_params[dir] = dma_params;
-
-	/*
-	 * The snd_soc_pcm_stream->dma_data field is only used to communicate
-	 * the appropriate DMA parameters to the pcm driver hw_params()
-	 * function.  It should not be used for other purposes
-	 * as it is common to all substreams.
-	 */
-	snd_soc_dai_set_dma_data(rtd->cpu_dai, substream, dma_params);
+	dma_params = ssc_p->dma_params[dir];
 
 	channels = params_channels(params);