dmaengine: at_hdmac: pause: no need to wait for FIFO empty

With the addition of the "pause" feature, an active wait was introduced
to check the "FIFO empty" event. This event was not always happening and
a timout contition was needed.
But, in some cases, this event depend on the peripheral connected to the
channel that is paused: FIFO becomes empty if the peripheral consumes data.
The timeout is pretty difficult to evaluate. Moreover, this check is not
needed.
In conclusion, it seems sensible to entirely remove the checking of
"FIFO empty" status when pausing.
Signed-off-by: NNicolas Ferre <nicolas.ferre@atmel.com>
[commit msg edited for grammer]
Signed-off-by: NVinod Koul <vinod.koul@intel.com>

drivers/dma/at_hdmac.c

@@ -933,25 +933,9 @@ static int atc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
 	dev_vdbg(chan2dev(chan), "atc_control (%d)\n", cmd);
 
 	if (cmd == DMA_PAUSE) {
-		int pause_timeout = 1000;
-
 		spin_lock_bh(&atchan->lock);
 
 		dma_writel(atdma, CHER, AT_DMA_SUSP(chan_id));
-
-		/* wait for FIFO to be empty */
-		while (!(dma_readl(atdma, CHSR) & AT_DMA_EMPT(chan_id))) {
-			if (pause_timeout-- > 0) {
-				/* the FIFO can only drain if the peripheral
-				 * is still requesting data:
-				 * -> timeout if it is not the case. */
-				dma_writel(atdma, CHDR, AT_DMA_RES(chan_id));
-				spin_unlock_bh(&atchan->lock);
-				return -ETIMEDOUT;
-			}
-			cpu_relax();
-		}
-
 		set_bit(ATC_IS_PAUSED, &atchan->status);
 
 		spin_unlock_bh(&atchan->lock);