USB: ehci: report Data Buffer Error in debug mode

Data Buffer Error as per spec section 4.15.1.1.2
results when there is Underrun or Overrun condition.

This error is considered non-fatal and never gets reported.
Its a very good indication on things going wrong at system level,
like running memory at much slower speed.

This is a good error to flag allowing system level corrections.

An issue was found with OMAP4460 board where DDR had to be run
at full speed and this logging helped.
Signed-off-by: Vikram Pandita <vikram.pandita@ti.com>
Reviewed-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Vikram Pandita <vikram.pandita@ti.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/ehci-q.c

@@ -373,6 +373,17 @@ qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh)
  retry_xacterr:
 		if ((token & QTD_STS_ACTIVE) == 0) {
 
+			/* Report Data Buffer Error: non-fatal but useful */
+			if (token & QTD_STS_DBE)
+				ehci_dbg(ehci,
+					"detected DataBufferErr for urb %p ep%d%s len %d, qtd %p [qh %p]\n",
+					urb,
+					usb_endpoint_num(&urb->ep->desc),
+					usb_endpoint_dir_in(&urb->ep->desc) ? "in" : "out",
+					urb->transfer_buffer_length,
+					qtd,
+					qh);
+
 			/* on STALL, error, and short reads this urb must
 			 * complete and all its qtds must be recycled.
 			 */