xhci: Stop unnecessary tracking of free trbs in a ring

[platform/kernel/linux-rpi.git] / drivers / usb / host / xhci-ring.c

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 2722dca..646ff12 100644 (file)
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -174,12 +174,10 @@ void inc_deq(struct xhci_hcd *xhci, struct xhci_ring *ring)
 
        /* All other rings have link trbs */
        if (!trb_is_link(ring->dequeue)) {
-               if (last_trb_on_seg(ring->deq_seg, ring->dequeue)) {
+               if (last_trb_on_seg(ring->deq_seg, ring->dequeue))
                        xhci_warn(xhci, "Missing link TRB at end of segment\n");
-               } else {
+               else
                        ring->dequeue++;
-                       ring->num_trbs_free++;
-               }
        }
 
        while (trb_is_link(ring->dequeue)) {
@@ -221,9 +219,6 @@ static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring,
        unsigned int link_trb_count = 0;
 
        chain = le32_to_cpu(ring->enqueue->generic.field[3]) & TRB_CHAIN;
-       /* If this is not event ring, there is one less usable TRB */
-       if (!trb_is_link(ring->enqueue))
-               ring->num_trbs_free--;
 
        if (last_trb_on_seg(ring->enq_seg, ring->enqueue)) {
                xhci_err(xhci, "Tried to move enqueue past ring segment\n");
@@ -276,24 +271,40 @@ static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring,
        trace_xhci_inc_enq(ring);
 }
 
-static int xhci_num_trbs_to(struct xhci_segment *start_seg, union xhci_trb *start,
-                           struct xhci_segment *end_seg, union xhci_trb *end,
-                           unsigned int num_segs)
+/*
+ * Return number of free normal TRBs from enqueue to dequeue pointer on ring.
+ * Not counting an assumed link TRB at end of each TRBS_PER_SEGMENT sized segment.
+ * Only for transfer and command rings where driver is the producer, not for
+ * event rings.
+ */
+static unsigned int xhci_num_trbs_free(struct xhci_hcd *xhci, struct xhci_ring *ring)
 {
+       struct xhci_segment *enq_seg = ring->enq_seg;
+       union xhci_trb *enq = ring->enqueue;
        union xhci_trb *last_on_seg;
-       int num = 0;
+       unsigned int free = 0;
        int i = 0;
 
+       /* Ring might be empty even if enq != deq if enq is left on a link trb */
+       if (trb_is_link(enq)) {
+               enq_seg = enq_seg->next;
+               enq = enq_seg->trbs;
+       }
+
+       /* Empty ring, common case, don't walk the segments */
+       if (enq == ring->dequeue)
+               return ring->num_segs * (TRBS_PER_SEGMENT - 1);
+
        do {
-               if (start_seg == end_seg && end >= start)
-                       return num + (end - start);
-               last_on_seg = &start_seg->trbs[TRBS_PER_SEGMENT - 1];
-               num += last_on_seg - start;
-               start_seg = start_seg->next;
-               start = start_seg->trbs;
-       } while (i++ <= num_segs);
-
-       return -EINVAL;
+               if (ring->deq_seg == enq_seg && ring->dequeue >= enq)
+                       return free + (ring->dequeue - enq);
+               last_on_seg = &enq_seg->trbs[TRBS_PER_SEGMENT - 1];
+               free += last_on_seg - enq;
+               enq_seg = enq_seg->next;
+               enq = enq_seg->trbs;
+       } while (i++ <= ring->num_segs);
+
+       return free;
 }
 
 /*
@@ -1291,10 +1302,7 @@ static void update_ring_for_set_deq_completion(struct xhci_hcd *xhci,
                unsigned int ep_index)
 {
        union xhci_trb *dequeue_temp;
-       int num_trbs_free_temp;
-       bool revert = false;
 
-       num_trbs_free_temp = ep_ring->num_trbs_free;
        dequeue_temp = ep_ring->dequeue;
 
        /* If we get two back-to-back stalls, and the first stalled transfer
@@ -1310,7 +1318,6 @@ static void update_ring_for_set_deq_completion(struct xhci_hcd *xhci,
 
        while (ep_ring->dequeue != dev->eps[ep_index].queued_deq_ptr) {
                /* We have more usable TRBs */
-               ep_ring->num_trbs_free++;
                ep_ring->dequeue++;
                if (trb_is_link(ep_ring->dequeue)) {
                        if (ep_ring->dequeue ==
@@ -1320,15 +1327,10 @@ static void update_ring_for_set_deq_completion(struct xhci_hcd *xhci,
                        ep_ring->dequeue = ep_ring->deq_seg->trbs;
                }
                if (ep_ring->dequeue == dequeue_temp) {
-                       revert = true;
+                       xhci_dbg(xhci, "Unable to find new dequeue pointer\n");
                        break;
                }
        }
-
-       if (revert) {
-               xhci_dbg(xhci, "Unable to find new dequeue pointer\n");
-               ep_ring->num_trbs_free = num_trbs_free_temp;
-       }
 }
 
 /*
@@ -2183,7 +2185,6 @@ static int finish_td(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
                     u32 trb_comp_code)
 {
        struct xhci_ep_ctx *ep_ctx;
-       int trbs_freed;
 
        ep_ctx = xhci_get_ep_ctx(xhci, ep->vdev->out_ctx, ep->ep_index);
 
@@ -2253,13 +2254,6 @@ static int finish_td(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
        }
 
        /* Update ring dequeue pointer */
-       trbs_freed = xhci_num_trbs_to(ep_ring->deq_seg, ep_ring->dequeue,
-                                     td->last_trb_seg, td->last_trb,
-                                     ep_ring->num_segs);
-       if (trbs_freed < 0)
-               xhci_dbg(xhci, "Failed to count freed trbs at TD finish\n");
-       else
-               ep_ring->num_trbs_free += trbs_freed;
        ep_ring->dequeue = td->last_trb;
        ep_ring->deq_seg = td->last_trb_seg;
        inc_deq(xhci, ep_ring);
@@ -2483,7 +2477,6 @@ static int skip_isoc_td(struct xhci_hcd *xhci, struct xhci_td *td,
        /* Update ring dequeue pointer */
        ep->ring->dequeue = td->last_trb;
        ep->ring->deq_seg = td->last_trb_seg;
-       ep->ring->num_trbs_free += td->num_trbs - 1;
        inc_deq(xhci, ep->ring);
 
        return xhci_td_cleanup(xhci, td, ep->ring, status);
@@ -3227,7 +3220,7 @@ static int prepare_ring(struct xhci_hcd *xhci, struct xhci_ring *ep_ring,
 
        if (ep_ring != xhci->cmd_ring) {
                new_segs = xhci_ring_expansion_needed(xhci, ep_ring, num_trbs);
-       } else if (ep_ring->num_trbs_free <= num_trbs) {
+       } else if (xhci_num_trbs_free(xhci, ep_ring) <= num_trbs) {
                xhci_err(xhci, "Do not support expand command ring\n");
                return -ENOMEM;
        }
@@ -4205,7 +4198,6 @@ cleanup:
        ep_ring->enqueue = urb_priv->td[0].first_trb;
        ep_ring->enq_seg = urb_priv->td[0].start_seg;
        ep_ring->cycle_state = start_cycle;
-       ep_ring->num_trbs_free = ep_ring->num_trbs_free_temp;
        usb_hcd_unlink_urb_from_ep(bus_to_hcd(urb->dev->bus), urb);
        return ret;
 }
@@ -4287,7 +4279,6 @@ int xhci_queue_isoc_tx_prepare(struct xhci_hcd *xhci, gfp_t mem_flags,
        }
 
 skip_start_over:
-       ep_ring->num_trbs_free_temp = ep_ring->num_trbs_free;
 
        return xhci_queue_isoc_tx(xhci, mem_flags, urb, slot_id, ep_index);
 }