1 files changed, 46 insertions, 16 deletions

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9012098add6b..94e6934edb09 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -182,8 +182,12 @@ static void inc_deq(struct xhci_hcd *xhci, struct xhci_ring *ring, bool consumer
  * set, but other sections talk about dealing with the chain bit set.  This was
  * fixed in the 0.96 specification errata, but we have to assume that all 0.95
  * xHCI hardware can't handle the chain bit being cleared on a link TRB.
+ *
+ * @more_trbs_coming:   Will you enqueue more TRBs before calling
+ *                      prepare_transfer()?
  */
-static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring, bool consumer)
+static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring,
+                bool consumer, bool more_trbs_coming)
 {
         u32 chain;
         union xhci_trb *next;
@@ -199,15 +203,28 @@ 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 (chain) {
-                                        next->link.control |= TRB_CHAIN;
-
-                                        /* Give this link TRB to the hardware */
-                                        wmb();
-                                        next->link.control ^= TRB_CYCLE;
-                                } else {
+                                /*
+                                 * If the caller doesn't plan on enqueueing more
+                                 * TDs before ringing the doorbell, then we
+                                 * don't want to give the link TRB to the
+                                 * hardware just yet.  We'll give the link TRB
+                                 * back in prepare_ring() just before we enqueue
+                                 * the TD at the top of the ring.
+                                 */
+                                if (!chain && !more_trbs_coming)
                                         break;
+
+                                /* 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;
                                 }
+                                /* Give this link TRB to the hardware */
+                                wmb();
+                                next->link.control ^= TRB_CYCLE;
                         }
                         /* Toggle the cycle bit after the last ring segment. */
                         if (last_trb_on_last_seg(xhci, ring, ring->enq_seg, next)) {
@@ -1707,9 +1724,12 @@ void xhci_handle_event(struct xhci_hcd *xhci)
 /*
  * Generic function for queueing a TRB on a ring.
  * The caller must have checked to make sure there's room on the ring.
+ *
+ * @more_trbs_coming:   Will you enqueue more TRBs before calling
+ *                      prepare_transfer()?
  */
 static void queue_trb(struct xhci_hcd *xhci, struct xhci_ring *ring,
-                bool consumer,
+                bool consumer, bool more_trbs_coming,
                 u32 field1, u32 field2, u32 field3, u32 field4)
 {
         struct xhci_generic_trb *trb;
@@ -1719,7 +1739,7 @@ static void queue_trb(struct xhci_hcd *xhci, struct xhci_ring *ring,
         trb->field[1] = field2;
         trb->field[2] = field3;
         trb->field[3] = field4;
-        inc_enq(xhci, ring, consumer);
+        inc_enq(xhci, ring, consumer, more_trbs_coming);
 }
 
 /*
@@ -1988,6 +2008,7 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
         int trb_buff_len, this_sg_len, running_total;
         bool first_trb;
         u64 addr;
+        bool more_trbs_coming;
 
         struct xhci_generic_trb *start_trb;
         int start_cycle;
@@ -2073,7 +2094,11 @@ static int queue_bulk_sg_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
                 length_field = TRB_LEN(trb_buff_len) |
                         remainder |
                         TRB_INTR_TARGET(0);
-                queue_trb(xhci, ep_ring, false,
+                if (num_trbs > 1)
+                        more_trbs_coming = true;
+                else
+                        more_trbs_coming = false;
+                queue_trb(xhci, ep_ring, false, more_trbs_coming,
                                 lower_32_bits(addr),
                                 upper_32_bits(addr),
                                 length_field,
@@ -2124,6 +2149,7 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
         int num_trbs;
         struct xhci_generic_trb *start_trb;
         bool first_trb;
+        bool more_trbs_coming;
         int start_cycle;
         u32 field, length_field;
 
@@ -2212,7 +2238,11 @@ int xhci_queue_bulk_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
                 length_field = TRB_LEN(trb_buff_len) |
                         remainder |
                         TRB_INTR_TARGET(0);
-                queue_trb(xhci, ep_ring, false,
+                if (num_trbs > 1)
+                        more_trbs_coming = true;
+                else
+                        more_trbs_coming = false;
+                queue_trb(xhci, ep_ring, false, more_trbs_coming,
                                 lower_32_bits(addr),
                                 upper_32_bits(addr),
                                 length_field,
@@ -2291,7 +2321,7 @@ int xhci_queue_ctrl_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
         /* Queue setup TRB - see section 6.4.1.2.1 */
         /* FIXME better way to translate setup_packet into two u32 fields? */
         setup = (struct usb_ctrlrequest *) urb->setup_packet;
-        queue_trb(xhci, ep_ring, false,
+        queue_trb(xhci, ep_ring, false, true,
                         /* FIXME endianness is probably going to bite my ass here. */
                         setup->bRequestType | setup->bRequest << 8 | setup->wValue << 16,
                         setup->wIndex | setup->wLength << 16,
@@ -2307,7 +2337,7 @@ int xhci_queue_ctrl_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
         if (urb->transfer_buffer_length > 0) {
                 if (setup->bRequestType & USB_DIR_IN)
                         field |= TRB_DIR_IN;
-                queue_trb(xhci, ep_ring, false,
+                queue_trb(xhci, ep_ring, false, true,
                                 lower_32_bits(urb->transfer_dma),
                                 upper_32_bits(urb->transfer_dma),
                                 length_field,
@@ -2324,7 +2354,7 @@ int xhci_queue_ctrl_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
                 field = 0;
         else
                 field = TRB_DIR_IN;
-        queue_trb(xhci, ep_ring, false,
+        queue_trb(xhci, ep_ring, false, false,
                         0,
                         0,
                         TRB_INTR_TARGET(0),
@@ -2361,7 +2391,7 @@ static int queue_command(struct xhci_hcd *xhci, u32 field1, u32 field2,
                                         "unfailable commands failed.\n");
                 return -ENOMEM;
         }
-        queue_trb(xhci, xhci->cmd_ring, false, field1, field2, field3,
+        queue_trb(xhci, xhci->cmd_ring, false, false, field1, field2, field3,
                         field4 | xhci->cmd_ring->cycle_state);
         return 0;
 }