dmaengine: imx-sdma: find desc first in sdma_tx_status

In sdma_tx_status() we must first find the current sdma_desc. In cyclic
mode we assume that this can always be found with vchan_find_desc().
This is true because do not remove the current descriptor from the
desc_issued list:

	/*
	 * Do not delete the node in desc_issued list in cyclic mode, otherwise
	 * the desc allocated will never be freed in vchan_dma_desc_free_list
	 */
	if (!(sdmac->flags & IMX_DMA_SG_LOOP))
		list_del(&vd->node);

We will change this in the next step, so check if the current descriptor is
the desired one also for the cyclic case.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Link: https://lore.kernel.org/r/20191216105328.15198-9-s.hauer@pengutronix.deSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/imx-sdma.c

@@ -1648,7 +1648,7 @@ static enum dma_status sdma_tx_status(struct dma_chan *chan,
 				      struct dma_tx_state *txstate)
 {
 	struct sdma_channel *sdmac = to_sdma_chan(chan);
-	struct sdma_desc *desc;
+	struct sdma_desc *desc = NULL;
 	u32 residue;
 	struct virt_dma_desc *vd;
 	enum dma_status ret;
@@ -1659,19 +1659,23 @@ static enum dma_status sdma_tx_status(struct dma_chan *chan,
 		return ret;
 
 	spin_lock_irqsave(&sdmac->vc.lock, flags);
+
 	vd = vchan_find_desc(&sdmac->vc, cookie);
-	if (vd) {
+	if (vd)
 		desc = to_sdma_desc(&vd->tx);
+	else if (sdmac->desc && sdmac->desc->vd.tx.cookie == cookie)
+		desc = sdmac->desc;
+
+	if (desc) {
 		if (sdmac->flags & IMX_DMA_SG_LOOP)
 			residue = (desc->num_bd - desc->buf_ptail) *
 				desc->period_len - desc->chn_real_count;
 		else
 			residue = desc->chn_count - desc->chn_real_count;
-	} else if (sdmac->desc && sdmac->desc->vd.tx.cookie == cookie) {
-		residue = sdmac->desc->chn_count - sdmac->desc->chn_real_count;
 	} else {
 		residue = 0;
 	}
+
 	spin_unlock_irqrestore(&sdmac->vc.lock, flags);
 
 	dma_set_tx_state(txstate, chan->completed_cookie, chan->cookie,