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authorAlan Stern <stern@rowland.harvard.edu>2012-11-26 12:36:21 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-12-17 10:49:04 -0800
commite22045df6987c7d8edf69aa4fcee4720ee317158 (patch)
tree60151fdd7868f738da25daeb2036ce0bf34e5b3e
parentffedea0f00a4b38c3ce0913b22b742443ab2b03d (diff)
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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>
-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 dd24fc1..e66eb29 100644
--- a/drivers/usb/host/ohci-q.c
+++ b/drivers/usb/host/ohci-q.c
@@ -1130,6 +1130,25 @@ 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;
}