ASoC: PXA: Fix oops in __pxa2xx_pcm_prepare

pxa2xx_pcm_hw_free frees dma channel and sets prtd->dma_ch to -1,
but does not set prtd->params to NULL, so if pxa2xx_pcm_hw_params will
be called immediately, it leaves prtd->dma_ch initialized with -1,
and it results in oops in __pxa2xx_pcm_prepare. This bug is triggered
via SDL.

This patch adds check for prtd->dma_ch to __pxa2xx_pcm_prepare and
cleans prtd->params, so now it works properly.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/sound/arm/pxa2xx-pcm-lib.c b/sound/arm/pxa2xx-pcm-lib.c
index 8808b82311b1..76e0d5695075 100644
--- a/sound/arm/pxa2xx-pcm-lib.c
+++ b/sound/arm/pxa2xx-pcm-lib.c
@@ -140,6 +140,9 @@ int __pxa2xx_pcm_prepare(struct snd_pcm_substream *substream)
         if (!prtd || !prtd->params)
                 return 0;
 
+        if (prtd->dma_ch == -1)
+                return -EINVAL;
+
         DCSR(prtd->dma_ch) &= ~DCSR_RUN;
         DCSR(prtd->dma_ch) = 0;
         DCMD(prtd->dma_ch) = 0;