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authorAlan Stern <stern@rowland.harvard.edu>2012-11-26 12:36:21 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-11-26 17:57:20 -0500
commit50ce5c0683aa83eb161624ea89daa5a9eee0c2ce (patch)
tree52289863b53a3c1c7e911089db7094920c41f16a /drivers/usb/host
parent31b6a1048b7292efff8b5b53ae3d9d29adde385e (diff)
USB: OHCI: workaround for hardware bug: retired TDs not added to the Done Queue
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> CC: <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/host')
-rw-r--r--drivers/usb/host/ohci-q.c19
1 files changed, 19 insertions, 0 deletions
diff --git a/drivers/usb/host/ohci-q.c b/drivers/usb/host/ohci-q.c
index 177a213790d..7482cfbe8c5 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)
1128 1128
1129 while (td) { 1129 while (td) {
1130 struct td *td_next = td->next_dl_td; 1130 struct td *td_next = td->next_dl_td;
1131 struct ed *ed = td->ed;
1132
1133 /*
1134 * Some OHCI controllers (NVIDIA for sure, maybe others)
1135 * occasionally forget to add TDs to the done queue. Since
1136 * TDs for a given endpoint are always processed in order,
1137 * if we find a TD on the donelist then all of its
1138 * predecessors must be finished as well.
1139 */
1140 for (;;) {
1141 struct td *td2;
1142
1143 td2 = list_first_entry(&ed->td_list, struct td,
1144 td_list);
1145 if (td2 == td)
1146 break;
1147 takeback_td(ohci, td2);
1148 }
1149
1131 takeback_td(ohci, td); 1150 takeback_td(ohci, td);
1132 td = td_next; 1151 td = td_next;
1133 } 1152 }