usb: gadget: core: unmap request from DMA only if previously mapped

In the SG case this is already handled since a non-zero
request->num_mapped_sgs is a clear indicator that dma_map_sg()
had been called. While it would be nice to do the same for the
singly mapped case by simply checking for non-zero request->dma,
it's conceivable that 0 is a valid dma_addr_t handle. Hence add
a flag 'dma_mapped' to struct usb_request and use this to
determine the need to call dma_unmap_single(). Otherwise, if a
request is not DMA mapped then the result of calling
usb_request_unmap_request() would safely be a no-op.
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/udc/core.c

@@ -812,6 +812,8 @@ int usb_gadget_map_request_by_dev(struct device *dev,
 			dev_err(dev, "failed to map buffer\n");
 			return -EFAULT;
 		}
+
+		req->dma_mapped = 1;
 	}
 
 	return 0;
@@ -836,9 +838,10 @@ void usb_gadget_unmap_request_by_dev(struct device *dev,
 				is_in ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
 
 		req->num_mapped_sgs = 0;
-	} else {
+	} else if (req->dma_mapped) {
 		dma_unmap_single(dev, req->dma, req->length,
 				is_in ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
+		req->dma_mapped = 0;
 	}
 }
 EXPORT_SYMBOL_GPL(usb_gadget_unmap_request_by_dev);

include/linux/usb/gadget.h

@@ -48,6 +48,7 @@ struct usb_ep;
  *     by adding a zero length packet as needed;
  * @short_not_ok: When reading data, makes short packets be
  *     treated as errors (queue stops advancing till cleanup).
+ * @dma_mapped: Indicates if request has been mapped to DMA (internal)
  * @complete: Function called when request completes, so this request and
  *	its buffer may be re-used.  The function will always be called with
  *	interrupts disabled, and it must not sleep.
@@ -103,6 +104,7 @@ struct usb_request {
 	unsigned		no_interrupt:1;
 	unsigned		zero:1;
 	unsigned		short_not_ok:1;
+	unsigned		dma_mapped:1;
 
 	void			(*complete)(struct usb_ep *ep,
 					struct usb_request *req);