usb: dwc2: Disable descriptor dma mode by default

Even though the IP supports Descriptor DMA mode, it does not support SPLIT
transactions in this mode. So the driver, in its currently form, will not
support LS/FS devices when connected to a HS Hub if Descriptor DMA mode is
enabled.

So we should just default to disable descriptor dma mode.

Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc2/platform.c

@@ -134,6 +134,12 @@ static int dwc2_driver_probe(struct platform_device *dev)
 		/* Default all params to autodetect */
 		dwc2_set_all_params(&defparams, -1);
 		params = &defparams;
+
+		/*
+		 * Disable descriptor dma mode by default as the HW can support
+		 * it, but does not support it for SPLIT transactions.
+		 */
+		defparams.dma_desc_enable = 0;
 	}
 
 	hsotg = devm_kzalloc(&dev->dev, sizeof(*hsotg), GFP_KERNEL);