dmaengine: of-dma: Add support for optional router configuration callback

Additional configuration for the DMA event router might be needed for a
channel which can not be done during device_alloc_chan_resources callback
since the router information is not yet present for the drivers.

If there is a need for additional configuration for the channel if DMA
router is in use, then the driver can implement the device_router_config
callback.

Signed-off-by: Peter Ujfalusi <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/of-dma.c

···
 		ofdma->dma_router->route_free(ofdma->dma_router->dev,
 					      route_data);
 	} else {
+		int ret = 0;
+
 		chan->router = ofdma->dma_router;
 		chan->route_data = route_data;
+
+		if (chan->device->device_router_config)
+			ret = chan->device->device_router_config(chan);
+
+		if (ret) {
+			dma_release_channel(chan);
+			chan = ERR_PTR(ret);
+		}
 	}
 
 	/*

include/linux/dmaengine.h

···
  *	by tx_status
  * @device_alloc_chan_resources: allocate resources and return the
  *	number of allocated descriptors
+ * @device_router_config: optional callback for DMA router configuration
  * @device_free_chan_resources: release DMA channel's resources
  * @device_prep_dma_memcpy: prepares a memcpy operation
  * @device_prep_dma_xor: prepares a xor operation
···
 	enum dma_residue_granularity residue_granularity;
 
 	int (*device_alloc_chan_resources)(struct dma_chan *chan);
+	int (*device_router_config)(struct dma_chan *chan);
 	void (*device_free_chan_resources)(struct dma_chan *chan);
 
 	struct dma_async_tx_descriptor *(*device_prep_dma_memcpy)(