This is a note to let you know that I've just added the patch titled
USB: OHCI: workaround for hardware bug: retired TDs not added to the
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-next branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will also be merged in the next major kernel release
during the merge window.
If you have any questions about this process, please let me know.
>From 50ce5c0683aa83eb161624ea89daa5a9eee0c2ce Mon Sep 17 00:00:00 2001
From: Alan Stern <[email protected]>
Date: Mon, 26 Nov 2012 12:36:21 -0500
Subject: 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 <[email protected]>
Tested-by: Oliver Neukum <[email protected]>
CC: <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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 177a213..7482cfb 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;
}
--
1.8.0.197.g5a90748
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