From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946036Ab2LNXJf (ORCPT ); Fri, 14 Dec 2012 18:09:35 -0500 Received: from mail.kernel.org ([198.145.19.201]:41329 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1945993Ab2LNXHN (ORCPT ); Fri, 14 Dec 2012 18:07:13 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , alan@lxorguk.ukuu.org.uk, Alan Stern , Oliver Neukum Subject: [ 18/27] USB: OHCI: workaround for hardware bug: retired TDs not added to the Done Queue Date: Fri, 14 Dec 2012 15:01:31 -0800 Message-Id: <20121214222255.428009233@linuxfoundation.org> X-Mailer: git-send-email 1.8.1.rc1.5.g7e0651a In-Reply-To: <20121214222251.229078963@linuxfoundation.org> References: <20121214222251.229078963@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.7-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alan Stern 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 Tested-by: Oliver Neukum Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/ohci-q.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) --- 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; }