dma: cppi41: start tear down only if channel is busy

Start the channel tear down only if the channel is busy, else just
bail out. In some cases its seen that by the time the tear down is
initiated the cppi completes the DMA, especially in ISOCH transfers.
Signed-off-by: George Cherian <george.cherian@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/cppi41.c

@@ -620,12 +620,15 @@ static int cppi41_stop_chan(struct dma_chan *chan)
 	u32 desc_phys;
 	int ret;
 
+	desc_phys = lower_32_bits(c->desc_phys);
+	desc_num = (desc_phys - cdd->descs_phys) / sizeof(struct cppi41_desc);
+	if (!cdd->chan_busy[desc_num])
+		return 0;
+
 	ret = cppi41_tear_down_chan(c);
 	if (ret)
 		return ret;
 
-	desc_phys = lower_32_bits(c->desc_phys);
-	desc_num = (desc_phys - cdd->descs_phys) / sizeof(struct cppi41_desc);
 	WARN_ON(!cdd->chan_busy[desc_num]);
 	cdd->chan_busy[desc_num] = NULL;