dmaengine: split out pause/resume operations from device_control

Split out the pause and resume operations to callbacks of their own. In order
to preserve some backwark compatibility, the dmaengine_pause/dmaengine_resume
are still falling back on dmaengine_device_control.

Eventually, that will allow to get the device capabilities in a generic way,
removing the need to implement device_slave_caps.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

include/linux/dmaengine.h

@@ -612,6 +612,10 @@ struct dma_tx_state {
  *	code
  * @device_control: manipulate all pending operations on a channel, returns
  *	zero or error code
+ * @device_pause: Pauses any transfer happening on a channel. Returns
+ *	0 or an error code
+ * @device_resume: Resumes any transfer on a channel previously
+ *	paused. Returns 0 or an error code
  * @device_tx_status: poll for transaction completion, the optional
  *	txstate parameter can be supplied with a pointer to get a
  *	struct with auxiliary transfer status information, otherwise the call
@@ -681,6 +685,8 @@ struct dma_device {
 			     struct dma_slave_config *config);
 	int (*device_control)(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
 		unsigned long arg);
+	int (*device_pause)(struct dma_chan *chan);
+	int (*device_resume)(struct dma_chan *chan);
 
 	enum dma_status (*device_tx_status)(struct dma_chan *chan,
 					    dma_cookie_t cookie,
@@ -795,11 +801,17 @@ static inline int dmaengine_terminate_all(struct dma_chan *chan)
 
 static inline int dmaengine_pause(struct dma_chan *chan)
 {
+	if (chan->device->device_pause)
+		return chan->device->device_pause(chan);
+
 	return dmaengine_device_control(chan, DMA_PAUSE, 0);
 }
 
 static inline int dmaengine_resume(struct dma_chan *chan)
 {
+	if (chan->device->device_resume)
+		return chan->device->device_resume(chan);
+
 	return dmaengine_device_control(chan, DMA_RESUME, 0);
 }