USB: EHCI: fix counting of transaction error retries

This patch (as1274) simplifies the counting of transaction-error
retries.  Now we will count up from 0 to QH_XACTERR_MAX instead of
down from QH_XACTERR_MAX to 0.

The patch also fixes a small bug: qh->xacterr was not getting
initialized for interrupt endpoints.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Matthijs Kooijman <matthijs@stdin.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/ehci-q.c

@@ -375,12 +375,11 @@ qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh)
 				 */
 				if ((token & QTD_STS_XACT) &&
 						QTD_CERR(token) == 0 &&
-						--qh->xacterrs > 0 &&
+						++qh->xacterrs < QH_XACTERR_MAX &&
 						!urb->unlinked) {
 					ehci_dbg(ehci,
 	"detected XactErr len %zu/%zu retry %d\n",
-	qtd->length - QTD_LENGTH(token), qtd->length,
-	QH_XACTERR_MAX - qh->xacterrs);
+	qtd->length - QTD_LENGTH(token), qtd->length, qh->xacterrs);
 
 					/* reset the token in the qtd and the
 					 * qh overlay (which still contains
@@ -494,7 +493,7 @@ halt:
 		last = qtd;
 
 		/* reinit the xacterr counter for the next qtd */
-		qh->xacterrs = QH_XACTERR_MAX;
+		qh->xacterrs = 0;
 	}
 
 	/* last urb's completion might still need calling */
@@ -941,7 +940,7 @@ static void qh_link_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
 	head->hw_next = dma;
 
 	qh_get(qh);
-	qh->xacterrs = QH_XACTERR_MAX;
+	qh->xacterrs = 0;
 	qh->qh_state = QH_STATE_LINKED;
 	/* qtd completions reported later by interrupt */
 }

drivers/usb/host/ehci-sched.c

@@ -542,6 +542,7 @@ static int qh_link_periodic (struct ehci_hcd *ehci, struct ehci_qh *qh)
 		}
 	}
 	qh->qh_state = QH_STATE_LINKED;
+	qh->xacterrs = 0;
 	qh_get (qh);
 
 	/* update per-qh bandwidth for usbfs */