[media] dmaengine: ipu-idmac: add support for the DMA_PAUSE control

To support multi-size buffers in the mx3_camera V4L2 driver we have to be
able to stop DMA on a channel without releasing descriptors and completely
halting the hardware. Use the DMA_PAUSE control to implement this mode.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Vinod Koul <vinod.koul@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/dma/ipu/ipu_idmac.c

@@ -1307,6 +1307,7 @@ static irqreturn_t idmac_interrupt(int irq, void *dev_id)
 	    ipu_submit_buffer(ichan, descnew, sgnew, ichan->active_buffer) < 0) {
 		callback = descnew->txd.callback;
 		callback_param = descnew->txd.callback_param;
+		list_del_init(&descnew->list);
 		spin_unlock(&ichan->lock);
 		if (callback)
 			callback(callback_param);
@@ -1428,17 +1429,32 @@ static int __idmac_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
 {
 	struct idmac_channel *ichan = to_idmac_chan(chan);
 	struct idmac *idmac = to_idmac(chan->device);
+	struct ipu *ipu = to_ipu(idmac);
+	struct list_head *list, *tmp;
 	unsigned long flags;
 	int i;
 
-	/* Only supports DMA_TERMINATE_ALL */
-	if (cmd != DMA_TERMINATE_ALL)
-		return -ENXIO;
+	switch (cmd) {
+	case DMA_PAUSE:
+		spin_lock_irqsave(&ipu->lock, flags);
+		ipu_ic_disable_task(ipu, chan->chan_id);
+
+		/* Return all descriptors into "prepared" state */
+		list_for_each_safe(list, tmp, &ichan->queue)
+			list_del_init(list);
+
+		ichan->sg[0] = NULL;
+		ichan->sg[1] = NULL;
+
+		spin_unlock_irqrestore(&ipu->lock, flags);
 
+		ichan->status = IPU_CHANNEL_INITIALIZED;
+		break;
+	case DMA_TERMINATE_ALL:
 		ipu_disable_channel(idmac, ichan,
 				    ichan->status >= IPU_CHANNEL_ENABLED);
 
-	tasklet_disable(&to_ipu(idmac)->tasklet);
+		tasklet_disable(&ipu->tasklet);
 
 		/* ichan->queue is modified in ISR, have to spinlock */
 		spin_lock_irqsave(&ichan->lock, flags);
@@ -1458,9 +1474,13 @@ static int __idmac_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
 		ichan->sg[1] = NULL;
 		spin_unlock_irqrestore(&ichan->lock, flags);
 
-	tasklet_enable(&to_ipu(idmac)->tasklet);
+		tasklet_enable(&ipu->tasklet);
 
 		ichan->status = IPU_CHANNEL_INITIALIZED;
+		break;
+	default:
+		return -ENOSYS;
+	}
 
 	return 0;
 }
@@ -1663,7 +1683,6 @@ static void __exit ipu_idmac_exit(struct ipu *ipu)
 		struct idmac_channel *ichan = ipu->channel + i;
 
 		idmac_control(&ichan->dma_chan, DMA_TERMINATE_ALL, 0);
-		idmac_prep_slave_sg(&ichan->dma_chan, NULL, 0, DMA_NONE, 0);
 	}
 
 	dma_async_device_unregister(&idmac->dma);