Greg:
Some old Intel UHCI controllers have a bug that has shown up in a few
systems (the PIIX3 "Neptune" chip set). Until now there has not been any
simple way to work around the bug, but the lastest changes in uhci-hcd
have made it easy. This patch (as684) adds the work-around.
Alan Stern
Signed-off-by: Alan Stern <[EMAIL PROTECTED]>
---
Index: usb-2.6/drivers/usb/host/uhci-q.c
===================================================================
--- usb-2.6.orig/drivers/usb/host/uhci-q.c
+++ usb-2.6/drivers/usb/host/uhci-q.c
@@ -13,7 +13,7 @@
* (C) Copyright 2000 Yggdrasil Computing, Inc. (port of new PCI interface
* support from usb-ohci.c by Adam Richter, [EMAIL PROTECTED]).
* (C) Copyright 1999 Gregory P. Smith (from usb-ohci.c)
- * (C) Copyright 2004-2005 Alan Stern, [EMAIL PROTECTED]
+ * (C) Copyright 2004-2006 Alan Stern, [EMAIL PROTECTED]
*/
@@ -1287,6 +1287,11 @@ restart:
* Check for queues that have made some forward progress.
* Returns 0 if the queue is not Isochronous, is ACTIVE, and
* has not advanced since last examined; 1 otherwise.
+ *
+ * Early Intel controllers have a bug which causes qh->element sometimes
+ * not to advance when a TD completes successfully. The queue remains
+ * stuck on the inactive completed TD. We detect such cases and advance
+ * the element pointer by hand.
*/
static int uhci_advance_check(struct uhci_hcd *uhci, struct uhci_qh *qh)
{
@@ -1327,6 +1332,15 @@ static int uhci_advance_check(struct uhc
/* The queue hasn't advanced; check for timeout */
if (!qh->wait_expired && time_after(jiffies,
qh->advance_jiffies + QH_WAIT_TIMEOUT)) {
+
+ /* Detect the Intel bug and work around it */
+ if (qh->post_td && qh_element(qh) ==
+ cpu_to_le32(qh->post_td->dma_handle)) {
+ qh->element = qh->post_td->link;
+ qh->advance_jiffies = jiffies;
+ return 1;
+ }
+
qh->wait_expired = 1;
/* If the current URB wants FSBR, unlink it temporarily
-------------------------------------------------------
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