UHCI: Fix problem caused by lack of terminating QH

This patch (as871) fixes a problem introduced by an earlier change.
It turns out that some systems really do need to have a terminating
skeleton QH present whenever FSBR is on.  I don't know any way to tell
which systems do need it and which don't; the easiest answer is to
have it there always.

This fixes the NumLock-hang bug reported by Jiri Slaby.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/uhci-debug.c

@@ -145,7 +145,8 @@ static int uhci_show_urbp(struct urb_priv *urbp, char *buf, int len, int space)
 	return out - buf;
 }
 
-static int uhci_show_qh(struct uhci_qh *qh, char *buf, int len, int space)
+static int uhci_show_qh(struct uhci_hcd *uhci,
+		struct uhci_qh *qh, char *buf, int len, int space)
 {
 	char *out = buf;
 	int i, nurbs;
@@ -190,6 +191,9 @@ static int uhci_show_qh(struct uhci_qh *qh, char *buf, int len, int space)
 
 	if (list_empty(&qh->queue)) {
 		out += sprintf(out, "%*s  queue is empty\n", space, "");
+		if (qh == uhci->skel_async_qh)
+			out += uhci_show_td(uhci->term_td, out,
+					len - (out - buf), 0);
 	} else {
 		struct urb_priv *urbp = list_entry(qh->queue.next,
 				struct urb_priv, node);
@@ -343,6 +347,7 @@ static int uhci_sprint_schedule(struct uhci_hcd *uhci, char *buf, int len)
 	struct list_head *tmp, *head;
 	int nframes, nerrs;
 	__le32 link;
+	__le32 fsbr_link;
 
 	static const char * const qh_names[] = {
 		"unlink", "iso", "int128", "int64", "int32", "int16",
@@ -424,21 +429,22 @@ static int uhci_sprint_schedule(struct uhci_hcd *uhci, char *buf, int len)
 
 	out += sprintf(out, "Skeleton QHs\n");
 
+	fsbr_link = 0;
 	for (i = 0; i < UHCI_NUM_SKELQH; ++i) {
 		int cnt = 0;
-		__le32 fsbr_link = 0;
 
 		qh = uhci->skelqh[i];
 		out += sprintf(out, "- skel_%s_qh\n", qh_names[i]); \
-		out += uhci_show_qh(qh, out, len - (out - buf), 4);
+		out += uhci_show_qh(uhci, qh, out, len - (out - buf), 4);
 
 		/* Last QH is the Terminating QH, it's different */
 		if (i == SKEL_TERM) {
 			if (qh_element(qh) != LINK_TO_TD(uhci->term_td))
 				out += sprintf(out, "    skel_term_qh element is not set to term_td!\n");
-			if (link == LINK_TO_QH(uhci->skel_term_qh))
-				goto check_qh_link;
-			continue;
+			link = fsbr_link;
+			if (!link)
+				link = LINK_TO_QH(uhci->skel_term_qh);
+			goto check_qh_link;
 		}
 
 		head = &qh->node;
@@ -448,7 +454,7 @@ static int uhci_sprint_schedule(struct uhci_hcd *uhci, char *buf, int len)
 			qh = list_entry(tmp, struct uhci_qh, node);
 			tmp = tmp->next;
 			if (++cnt <= 10)
-				out += uhci_show_qh(qh, out,
+				out += uhci_show_qh(uhci, qh, out,
 						len - (out - buf), 4);
 			if (!fsbr_link && qh->skel >= SKEL_FSBR)
 				fsbr_link = LINK_TO_QH(qh);
@@ -463,8 +469,6 @@ static int uhci_sprint_schedule(struct uhci_hcd *uhci, char *buf, int len)
 			link = LINK_TO_QH(uhci->skel_async_qh);
 		else if (!uhci->fsbr_is_on)
 			;
-		else if (fsbr_link)
-			link = fsbr_link;
 		else
 			link = LINK_TO_QH(uhci->skel_term_qh);
 check_qh_link:
@@ -573,8 +577,8 @@ static const struct file_operations uhci_debug_operations = {
 static inline void lprintk(char *buf)
 {}
 
-static inline int uhci_show_qh(struct uhci_qh *qh, char *buf,
-		int len, int space)
+static inline int uhci_show_qh(struct uhci_hcd *uhci,
+		struct uhci_qh *qh, char *buf, int len, int space)
 {
 	return 0;
 }

drivers/usb/host/uhci-hcd.c

@@ -632,7 +632,8 @@ static int uhci_start(struct usb_hcd *hcd)
 	 */
 	for (i = SKEL_ISO + 1; i < SKEL_ASYNC; ++i)
 		uhci->skelqh[i]->link = LINK_TO_QH(uhci->skel_async_qh);
-	uhci->skel_async_qh->link = uhci->skel_term_qh->link = UHCI_PTR_TERM;
+	uhci->skel_async_qh->link = UHCI_PTR_TERM;
+	uhci->skel_term_qh->link = LINK_TO_QH(uhci->skel_term_qh);
 
 	/* This dummy TD is to work around a bug in Intel PIIX controllers */
 	uhci_fill_td(uhci->term_td, 0, uhci_explen(0) |

drivers/usb/host/uhci-q.c

@@ -45,43 +45,27 @@ static inline void uhci_clear_next_interrupt(struct uhci_hcd *uhci)
  */
 static void uhci_fsbr_on(struct uhci_hcd *uhci)
 {
-	struct uhci_qh *fsbr_qh, *lqh, *tqh;
+	struct uhci_qh *lqh;
 
+	/* The terminating skeleton QH always points back to the first
+	 * FSBR QH.  Make the last async QH point to the terminating
+	 * skeleton QH. */
 	uhci->fsbr_is_on = 1;
 	lqh = list_entry(uhci->skel_async_qh->node.prev,
 			struct uhci_qh, node);
-
-	/* Find the first FSBR QH.  Linear search through the list is
-	 * acceptable because normally FSBR gets turned on as soon as
-	 * one QH needs it. */
-	fsbr_qh = NULL;
-	list_for_each_entry_reverse(tqh, &uhci->skel_async_qh->node, node) {
-		if (tqh->skel < SKEL_FSBR)
-			break;
-		fsbr_qh = tqh;
-	}
-
-	/* No FSBR QH means we must insert the terminating skeleton QH */
-	if (!fsbr_qh) {
-		uhci->skel_term_qh->link = LINK_TO_QH(uhci->skel_term_qh);
-		wmb();
-		lqh->link = uhci->skel_term_qh->link;
-
-	/* Otherwise loop the last QH to the first FSBR QH */
-	} else
-		lqh->link = LINK_TO_QH(fsbr_qh);
+	lqh->link = LINK_TO_QH(uhci->skel_term_qh);
 }
 
 static void uhci_fsbr_off(struct uhci_hcd *uhci)
 {
 	struct uhci_qh *lqh;
 
+	/* Remove the link from the last async QH to the terminating
+	 * skeleton QH. */
 	uhci->fsbr_is_on = 0;
 	lqh = list_entry(uhci->skel_async_qh->node.prev,
 			struct uhci_qh, node);
-
-	/* End the async list normally and unlink the terminating QH */
-	lqh->link = uhci->skel_term_qh->link = UHCI_PTR_TERM;
+	lqh->link = UHCI_PTR_TERM;
 }
 
 static void uhci_add_fsbr(struct uhci_hcd *uhci, struct urb *urb)
@@ -464,9 +448,8 @@ static void link_interrupt(struct uhci_hcd *uhci, struct uhci_qh *qh)
  */
 static void link_async(struct uhci_hcd *uhci, struct uhci_qh *qh)
 {
-	struct uhci_qh *pqh, *lqh;
+	struct uhci_qh *pqh;
 	__le32 link_to_new_qh;
-	__le32 *extra_link = &link_to_new_qh;
 
 	/* Find the predecessor QH for our new one and insert it in the list.
 	 * The list of QHs is expected to be short, so linear search won't
@@ -476,31 +459,17 @@ static void link_async(struct uhci_hcd *uhci, struct uhci_qh *qh)
 			break;
 	}
 	list_add(&qh->node, &pqh->node);
-	qh->link = pqh->link;
-
-	link_to_new_qh = LINK_TO_QH(qh);
-
-	/* If this is now the first FSBR QH, take special action */
-	if (uhci->fsbr_is_on && pqh->skel < SKEL_FSBR &&
-			qh->skel >= SKEL_FSBR) {
-		lqh = list_entry(uhci->skel_async_qh->node.prev,
-				struct uhci_qh, node);
-
-		/* If the new QH is also the last one, we must unlink
-		 * the terminating skeleton QH and make the new QH point
-		 * back to itself. */
-		if (qh == lqh) {
-			qh->link = link_to_new_qh;
-			extra_link = &uhci->skel_term_qh->link;
-
-		/* Otherwise the last QH must point to the new QH */
-		} else
-			extra_link = &lqh->link;
-	}
 
 	/* Link it into the schedule */
+	qh->link = pqh->link;
 	wmb();
-	*extra_link = pqh->link = link_to_new_qh;
+	link_to_new_qh = LINK_TO_QH(qh);
+	pqh->link = link_to_new_qh;
+
+	/* If this is now the first FSBR QH, link the terminating skeleton
+	 * QH to it. */
+	if (pqh->skel < SKEL_FSBR && qh->skel >= SKEL_FSBR)
+		uhci->skel_term_qh->link = link_to_new_qh;
 }
 
 /*
@@ -561,31 +530,16 @@ static void unlink_interrupt(struct uhci_hcd *uhci, struct uhci_qh *qh)
  */
 static void unlink_async(struct uhci_hcd *uhci, struct uhci_qh *qh)
 {
-	struct uhci_qh *pqh, *lqh;
+	struct uhci_qh *pqh;
 	__le32 link_to_next_qh = qh->link;
 
 	pqh = list_entry(qh->node.prev, struct uhci_qh, node);
-
-	/* If this is the first FSBQ QH, take special action */
-	if (uhci->fsbr_is_on && pqh->skel < SKEL_FSBR &&
-			qh->skel >= SKEL_FSBR) {
-		lqh = list_entry(uhci->skel_async_qh->node.prev,
-				struct uhci_qh, node);
-
-		/* If this QH is also the last one, we must link in
-		 * the terminating skeleton QH. */
-		if (qh == lqh) {
-			link_to_next_qh = LINK_TO_QH(uhci->skel_term_qh);
-			uhci->skel_term_qh->link = link_to_next_qh;
-			wmb();
-			qh->link = link_to_next_qh;
-
-		/* Otherwise the last QH must point to the new first FSBR QH */
-		} else
-			lqh->link = link_to_next_qh;
-	}
-
 	pqh->link = link_to_next_qh;
+
+	/* If this was the old first FSBR QH, link the terminating skeleton
+	 * QH to the next (new first FSBR) QH. */
+	if (pqh->skel < SKEL_FSBR && qh->skel >= SKEL_FSBR)
+		uhci->skel_term_qh->link = link_to_next_qh;
 	mb();
 }
 
@@ -1217,7 +1171,7 @@ static int uhci_result_common(struct uhci_hcd *uhci, struct urb *urb)
 
 				if (debug > 1 && errbuf) {
 					/* Print the chain for debugging */
-					uhci_show_qh(urbp->qh, errbuf,
+					uhci_show_qh(uhci, urbp->qh, errbuf,
 							ERRBUF_LEN, 0);
 					lprintk(errbuf);
 				}