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Commit b7116ebc authored by Sarah Sharp's avatar Sarah Sharp Committed by Greg Kroah-Hartman
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USB: xhci: Avoid compiler reordering in Link TRB giveback. 

Force the compiler to write the cycle bit of the Link TRB last.  This
ensures that the hardware doesn't think it owns the Link TRB before we set
the chain bit.  Reported by Oliver in this thread:
	http://marc.info/?l=linux-usb&m=124091532410219&w=2



Reported-by: default avatarOliver Neukum <oliver@neukum.org>
Signed-off-by: default avatarSarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent c96a2b81

drivers/usb/host/xhci-ring.c

+3 −2
Original line number Diff line number Diff line
@@ -183,13 +183,14 @@ static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring, bool consumer 
	while (last_trb(xhci, ring, ring->enq_seg, next)) {

		if (!consumer) {

			if (ring != xhci->event_ring) {

				next->link.control &= ~TRB_CHAIN;

				next->link.control |= chain;

				/* Give this link TRB to the hardware */

				wmb();

				if (next->link.control & TRB_CYCLE)

					next->link.control &= (u32) ~TRB_CYCLE;

				else

					next->link.control |= (u32) TRB_CYCLE;

				next->link.control &= ~TRB_CHAIN;

				next->link.control |= chain;

			}

			/* Toggle the cycle bit after the last ring segment. */

			if (last_trb_on_last_seg(xhci, ring, ring->enq_seg, next)) {