[3.5.y.z,extended,stable] Patch "USB: OHCI: workaround for hardware bug: retired TDs not" has been added to staging queue

Message ID 1357590884-18967-1-git-send-email-herton.krzesinski@canonical.com
State New
Headers show

Commit Message

Herton Ronaldo Krzesinski Jan. 7, 2013, 8:34 p.m.
This is a note to let you know that I have just added a patch titled

    USB: OHCI: workaround for hardware bug: retired TDs not

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



From 5bda64f9a5490728e980326ab687b3bc9b3854e6 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@rowland.harvard.edu>
Date: Mon, 26 Nov 2012 12:36:21 -0500
Subject: [PATCH] USB: OHCI: workaround for hardware bug: retired TDs not
 added to the Done Queue

commit 50ce5c0683aa83eb161624ea89daa5a9eee0c2ce upstream.

This patch (as1636) is a partial workaround for a hardware bug
affecting OHCI controllers by NVIDIA at least, maybe others too.  When
the controller retires a Transfer Descriptor, it is supposed to add
the TD onto the Done Queue.  But sometimes this doesn't happen, with
the result that ohci-hcd never realizes the corresponding transfer has
finished.  Symptoms can vary; a typical result is that USB audio stops
working after a while.

The patch works around the problem by recognizing that TDs are always
processed in order.  Therefore, if a later TD is found on the Done
Queue than all the earlier TDs for the same endpoint must be finished
as well.

Unfortunately this won't solve the problem in cases where the missing
TD is the last one in the endpoint's queue.  A complete fix would
require a signficant amount of change to the driver.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
 drivers/usb/host/ohci-q.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)



diff --git a/drivers/usb/host/ohci-q.c b/drivers/usb/host/ohci-q.c
index c5a1ea9..9d00d47 100644
--- a/drivers/usb/host/ohci-q.c
+++ b/drivers/usb/host/ohci-q.c
@@ -1128,6 +1128,25 @@  dl_done_list (struct ohci_hcd *ohci)

 	while (td) {
 		struct td	*td_next = td->next_dl_td;
+		struct ed	*ed = td->ed;
+		/*
+		 * Some OHCI controllers (NVIDIA for sure, maybe others)
+		 * occasionally forget to add TDs to the done queue.  Since
+		 * TDs for a given endpoint are always processed in order,
+		 * if we find a TD on the donelist then all of its
+		 * predecessors must be finished as well.
+		 */
+		for (;;) {
+			struct td	*td2;
+			td2 = list_first_entry(&ed->td_list, struct td,
+					td_list);
+			if (td2 == td)
+				break;
+			takeback_td(ohci, td2);
+		}
 		takeback_td(ohci, td);
 		td = td_next;