This is a note to let you know that I've just added the patch titled
USB: EHCI: don't check DMA values in QH overlays
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-linus 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 hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From feca7746d5d9e84b105a613b7f3b6ad00d327372 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Date: Fri, 1 Mar 2013 10:51:15 -0500
Subject: USB: EHCI: don't check DMA values in QH overlays
This patch (as1661) fixes a rather obscure bug in ehci-hcd. In a
couple of places, the driver compares the DMA address stored in a QH's
overlay region with the address of a particular qTD, in order to see
whether that qTD is the one currently being processed by the hardware.
(If it is then the status in the QH's overlay region is more
up-to-date than the status in the qTD, and if it isn't then the
overlay's value needs to be adjusted when the QH is added back to the
active schedule.)
However, DMA address in the overlay region isn't always valid. It
sometimes will contain a stale value, which may happen by coincidence
to be equal to a qTD's DMA address. Instead of checking the DMA
address, we should check whether the overlay region is active and
valid. The patch tests the ACTIVE bit in the overlay, and clears this
bit when the overlay becomes invalid (which happens when the
currently-executing URB is unlinked).
This is the second part of a fix for the regression reported at:
https://bugs.launchpad.net/bugs/1088733
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Reported-by: Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx>
Reported-and-tested-by: Stephen Thirlwall <sdt@xxxxxx>
CC: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/host/ehci-q.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index 7bf2b4e..5464665 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -135,7 +135,7 @@ qh_refresh (struct ehci_hcd *ehci, struct ehci_qh *qh)
* qtd is updated in qh_completions(). Update the QH
* overlay here.
*/
- if (cpu_to_hc32(ehci, qtd->qtd_dma) == qh->hw->hw_current) {
+ if (qh->hw->hw_token & ACTIVE_BIT(ehci)) {
qh->hw->hw_qtd_next = qtd->hw_next;
qtd = NULL;
}
@@ -449,11 +449,19 @@ qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh)
else if (last_status == -EINPROGRESS && !urb->unlinked)
continue;
- /* qh unlinked; token in overlay may be most current */
- if (state == QH_STATE_IDLE
- && cpu_to_hc32(ehci, qtd->qtd_dma)
- == hw->hw_current) {
+ /*
+ * If this was the active qtd when the qh was unlinked
+ * and the overlay's token is active, then the overlay
+ * hasn't been written back to the qtd yet so use its
+ * token instead of the qtd's. After the qtd is
+ * processed and removed, the overlay won't be valid
+ * any more.
+ */
+ if (state == QH_STATE_IDLE &&
+ qh->qtd_list.next == &qtd->qtd_list &&
+ (hw->hw_token & ACTIVE_BIT(ehci))) {
token = hc32_to_cpu(ehci, hw->hw_token);
+ hw->hw_token &= ~ACTIVE_BIT(ehci);
/* An unlink may leave an incomplete
* async transaction in the TT buffer.
--
1.8.1.2.434.g9a6c84e.dirty
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