更新ark-axi-dma.c解决播放音乐卡死问题

linux/drivers/dma/ark-axi-dma.c

@@ -967,6 +967,11 @@ static void axi_chan_block_xfer_complete(struct axi_dma_chan *chan)
 	/* The completed descriptor currently is in the head of vc list */
 	vd = vchan_next_desc(&chan->vc);
 
+	if (!vd) {
+		spin_unlock_irqrestore(&chan->vc.lock, flags);
+		return;
+	}
+
 	if (chan->cyclic) {
 		desc = vd_to_axi_desc(vd);
 		if (desc) {