ASoC: Tegra: tegra_pcm_deallocate_dma_buffer: Don't OOPS

Not all PCM devices have all sub-streams. Specifically, the SPDIF driver
only supports playback and hence has no capture substream. Check whether
a substream exists before dereferencing it, when de-allocating DMA
buffers in tegra_pcm_deallocate_dma_buffer.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: stable@kernel.org

1 files changed, 7 insertions, 2 deletions

diff --git a/sound/soc/tegra/tegra_pcm.c b/sound/soc/tegra/tegra_pcm.c
index ff86e5e3db68..c7cfd96e991e 100644
--- a/sound/soc/tegra/tegra_pcm.c
+++ b/sound/soc/tegra/tegra_pcm.c
@@ -309,9 +309,14 @@ static int tegra_pcm_preallocate_dma_buffer(struct snd_pcm *pcm, int stream)
 
 static void tegra_pcm_deallocate_dma_buffer(struct snd_pcm *pcm, int stream)
 {
-        struct snd_pcm_substream *substream = pcm->streams[stream].substream;
-        struct snd_dma_buffer *buf = &substream->dma_buffer;
+        struct snd_pcm_substream *substream;
+        struct snd_dma_buffer *buf;
+
+        substream = pcm->streams[stream].substream;
+        if (!substream)
+                return;
 
+        buf = &substream->dma_buffer;
         if (!buf->area)
                 return;