[ALSA] s3c24xx-pcm: fix hw_params dma handling

Since the PCM emulation can call multiple times to hw_setup(), but we
can only once allocate/request the DMA channel, we have to handle
this gracefully.

Signed-off-by: Harald Welte <laforge@openmoko.org>
Signed-off-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>

1 files changed, 13 insertions, 9 deletions

diff --git a/sound/soc/s3c24xx/s3c24xx-pcm.c b/sound/soc/s3c24xx/s3c24xx-pcm.c
index bfbdc3cbd43b..4107a87d4de3 100644
--- a/sound/soc/s3c24xx/s3c24xx-pcm.c
+++ b/sound/soc/s3c24xx/s3c24xx-pcm.c
@@ -158,18 +158,22 @@ static int s3c24xx_pcm_hw_params(struct snd_pcm_substream *substream,
         if (!dma)
                 return 0;
 
-        /* prepare DMA */
-        prtd->params = dma;
+        /* this may get called several times by oss emulation
+         * with different params -HW */
+        if (prtd->params == NULL) {
+                /* prepare DMA */
+                prtd->params = dma;
 
-        DBG("params %p, client %p, channel %d\n", prtd->params,
-                prtd->params->client, prtd->params->channel);
+                DBG("params %p, client %p, channel %d\n", prtd->params,
+                        prtd->params->client, prtd->params->channel);
 
-        ret = s3c2410_dma_request(prtd->params->channel,
-                                  prtd->params->client, NULL);
+                ret = s3c2410_dma_request(prtd->params->channel,
+                                          prtd->params->client, NULL);
 
-        if (ret) {
-                DBG(KERN_ERR "failed to get dma channel\n");
-                return ret;
+                if (ret) {
+                        DBG(KERN_ERR "failed to get dma channel\n");
+                        return ret;
+                }
         }
 
         /* channel needs configuring for mem=>device, increment memory addr,