USB: xhci: Transfer ring link TRB activation change.

Change transfer ring behavior to not follow/activate link TRBs
until active TRBs are queued after it.  This change affects
the behavior when a TD ends just before a link TRB.

Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 58 insertions, 13 deletions

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 15f02e88f32..803f6810e99 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -112,6 +112,12 @@ static inline int last_trb(struct xhci_hcd *xhci, struct xhci_ring *ring,
                 return (trb->link.control & TRB_TYPE_BITMASK) == TRB_TYPE(TRB_LINK);
 }
 
+static inline int enqueue_is_link_trb(struct xhci_ring *ring)
+{
+        struct xhci_link_trb *link = &ring->enqueue->link;
+        return ((link->control & TRB_TYPE_BITMASK) == TRB_TYPE(TRB_LINK));
+}
+
 /* Updates trb to point to the next TRB in the ring, and updates seg if the next
  * TRB is in a new segment.  This does not skip over link TRBs, and it does not
  * effect the ring dequeue or enqueue pointers.
@@ -193,20 +199,15 @@ 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) {
-                                /* If we're not dealing with 0.95 hardware,
-                                 * carry over the chain bit of the previous TRB
-                                 * (which may mean the chain bit is cleared).
-                                 */
-                                if (!xhci_link_trb_quirk(xhci)) {
-                                        next->link.control &= ~TRB_CHAIN;
-                                        next->link.control |= chain;
+                                if (chain) {
+                                        next->link.control |= TRB_CHAIN;
+
+                                        /* Give this link TRB to the hardware */
+                                        wmb();
+                                        next->link.control ^= TRB_CYCLE;
+                                } else {
+                                        break;
                                 }
-                                /* 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;
                         }
                         /* Toggle the cycle bit after the last ring segment. */
                         if (last_trb_on_last_seg(xhci, ring, ring->enq_seg, next)) {
@@ -245,6 +246,13 @@ static int room_on_ring(struct xhci_hcd *xhci, struct xhci_ring *ring,
         struct xhci_segment *cur_seg;
         unsigned int left_on_ring;
 
+        /* If we are currently pointing to a link TRB, advance the
+         * enqueue pointer before checking for space */
+        while (last_trb(xhci, ring, enq_seg, enq)) {
+                enq_seg = enq_seg->next;
+                enq = enq_seg->trbs;
+        }
+
         /* Check if ring is empty */
         if (enq == ring->dequeue) {
                 /* Can't use link trbs */
@@ -1728,6 +1736,43 @@ static int prepare_ring(struct xhci_hcd *xhci, struct xhci_ring *ep_ring,
                 xhci_err(xhci, "ERROR no room on ep ring\n");
                 return -ENOMEM;
         }
+
+        if (enqueue_is_link_trb(ep_ring)) {
+                struct xhci_ring *ring = ep_ring;
+                union xhci_trb *next;
+                unsigned long long addr;
+
+                xhci_dbg(xhci, "prepare_ring: pointing to link trb\n");
+                next = ring->enqueue;
+
+                while (last_trb(xhci, ring, ring->enq_seg, next)) {
+
+                        /* If we're not dealing with 0.95 hardware,
+                         * clear the chain bit.
+                         */
+                        if (!xhci_link_trb_quirk(xhci))
+                                next->link.control &= ~TRB_CHAIN;
+                        else
+                                next->link.control |= TRB_CHAIN;
+
+                        wmb();
+                        next->link.control ^= (u32) TRB_CYCLE;
+
+                        /* Toggle the cycle bit after the last ring segment. */
+                        if (last_trb_on_last_seg(xhci, ring, ring->enq_seg, next)) {
+                                ring->cycle_state = (ring->cycle_state ? 0 : 1);
+                                if (!in_interrupt()) {
+                                        xhci_dbg(xhci, "queue_trb: Toggle cycle "
+                                                "state for ring %p = %i\n",
+                                                ring, (unsigned int)ring->cycle_state);
+                                }
+                        }
+                        ring->enq_seg = ring->enq_seg->next;
+                        ring->enqueue = ring->enq_seg->trbs;
+                        next = ring->enqueue;
+                }
+        }
+
         return 0;
 }