xHCI: count free TRBs on transfer ring

In the past, the room_on_ring() check was implemented by walking all over
the ring, which is wasteful and complicated.

Count the number of free TRBs instead. The free TRBs number should be
updated when enqueue/dequeue pointer is updated, or upon the completion
of a set dequeue pointer command.

Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Tested-by: Paul Zimmerman <Paul.Zimmerman@synopsys.com>

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index bdea4de..212012c 100644 (file)
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -135,6 +135,12 @@ static void xhci_initialize_ring_info(struct xhci_ring *ring)
        /* Not necessary for new rings, but needed for re-initialized rings */
        ring->enq_updates = 0;
        ring->deq_updates = 0;
+
+       /*
+        * Each segment has a link TRB, and leave an extra TRB for SW
+        * accounting purpose
+        */
+       ring->num_trbs_free = ring->num_segs * (TRBS_PER_SEGMENT - 1) - 1;
 }
 
 /**

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index ad68a28..f9b6fa3 100644 (file)
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -145,10 +145,17 @@ static void next_trb(struct xhci_hcd *xhci,
  */
 static void inc_deq(struct xhci_hcd *xhci, struct xhci_ring *ring)
 {
-       union xhci_trb *next = ++(ring->dequeue);
+       union xhci_trb *next;
        unsigned long long addr;
 
        ring->deq_updates++;
+
+       /* If this is not event ring, there is one more usable TRB */
+       if (ring->type != TYPE_EVENT &&
+                       !last_trb(xhci, ring, ring->deq_seg, ring->dequeue))
+               ring->num_trbs_free++;
+       next = ++(ring->dequeue);
+
        /* Update the dequeue pointer further if that was a link TRB or we're at
         * the end of an event ring segment (which doesn't have link TRBS)
         */
@@ -189,6 +196,10 @@ static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring,
        unsigned long long addr;
 
        chain = le32_to_cpu(ring->enqueue->generic.field[3]) & TRB_CHAIN;
+       /* If this is not event ring, there is one less usable TRB */
+       if (ring->type != TYPE_EVENT &&
+                       !last_trb(xhci, ring, ring->enq_seg, ring->enqueue))
+               ring->num_trbs_free--;
        next = ++(ring->enqueue);
 
        ring->enq_updates++;
@@ -240,54 +251,14 @@ static void inc_enq(struct xhci_hcd *xhci, struct xhci_ring *ring,
 /*
  * Check to see if there's room to enqueue num_trbs on the ring.  See rules
  * above.
- * FIXME: this would be simpler and faster if we just kept track of the number
- * of free TRBs in a ring.
  */
-static int room_on_ring(struct xhci_hcd *xhci, struct xhci_ring *ring,
+static inline int room_on_ring(struct xhci_hcd *xhci, struct xhci_ring *ring,
                unsigned int num_trbs)
 {
-       int i;
-       union xhci_trb *enq = ring->enqueue;
-       struct xhci_segment *enq_seg = ring->enq_seg;
-       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 */
-               left_on_ring = TRBS_PER_SEGMENT - 1;
-               for (cur_seg = enq_seg->next; cur_seg != enq_seg;
-                               cur_seg = cur_seg->next)
-                       left_on_ring += TRBS_PER_SEGMENT - 1;
-
-               /* Always need one TRB free in the ring. */
-               left_on_ring -= 1;
-               if (num_trbs > left_on_ring) {
-                       xhci_warn(xhci, "Not enough room on ring; "
-                                       "need %u TRBs, %u TRBs left\n",
-                                       num_trbs, left_on_ring);
-                       return 0;
-               }
+       if (ring->num_trbs_free >= num_trbs)
                return 1;
-       }
-       /* Make sure there's an extra empty TRB available */
-       for (i = 0; i <= num_trbs; ++i) {
-               if (enq == ring->dequeue)
-                       return 0;
-               enq++;
-               while (last_trb(xhci, ring, enq_seg, enq)) {
-                       enq_seg = enq_seg->next;
-                       enq = enq_seg->trbs;
-               }
-       }
-       return 1;
+
+       return 0;
 }
 
 /* Ring the host controller doorbell after placing a command on the ring */
@@ -893,6 +864,43 @@ void xhci_stop_endpoint_command_watchdog(unsigned long arg)
        xhci_dbg(xhci, "xHCI host controller is dead.\n");
 }
 
+
+static void update_ring_for_set_deq_completion(struct xhci_hcd *xhci,
+               struct xhci_virt_device *dev,
+               struct xhci_ring *ep_ring,
+               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;
+
+       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 (last_trb(xhci, ep_ring, ep_ring->deq_seg,
+                               ep_ring->dequeue)) {
+                       if (ep_ring->dequeue ==
+                                       dev->eps[ep_index].queued_deq_ptr)
+                               break;
+                       ep_ring->deq_seg = ep_ring->deq_seg->next;
+                       ep_ring->dequeue = ep_ring->deq_seg->trbs;
+               }
+               if (ep_ring->dequeue == dequeue_temp) {
+                       revert = true;
+                       break;
+               }
+       }
+
+       if (revert) {
+               xhci_dbg(xhci, "Unable to find new dequeue pointer\n");
+               ep_ring->num_trbs_free = num_trbs_free_temp;
+       }
+}
+
 /*
  * When we get a completion for a Set Transfer Ring Dequeue Pointer command,
  * we need to clear the set deq pending flag in the endpoint ring state, so that
@@ -974,8 +982,8 @@ static void handle_set_deq_completion(struct xhci_hcd *xhci,
                        /* Update the ring's dequeue segment and dequeue pointer
                         * to reflect the new position.
                         */
-                       ep_ring->deq_seg = dev->eps[ep_index].queued_deq_seg;
-                       ep_ring->dequeue = dev->eps[ep_index].queued_deq_ptr;
+                       update_ring_for_set_deq_completion(xhci, dev,
+                               ep_ring, ep_index);
                } else {
                        xhci_warn(xhci, "Mismatch between completed Set TR Deq "
                                        "Ptr command & xHCI internal state.\n");
@@ -3407,6 +3415,7 @@ 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;
 }
@@ -3479,6 +3488,8 @@ int xhci_queue_isoc_tx_prepare(struct xhci_hcd *xhci, gfp_t mem_flags,
                                urb->dev->speed == USB_SPEED_FULL)
                        urb->interval /= 8;
        }
+       ep_ring->num_trbs_free_temp = ep_ring->num_trbs_free;
+
        return xhci_queue_isoc_tx(xhci, GFP_ATOMIC, urb, slot_id, ep_index);
 }
 

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 262400c..dec5b2d 100644 (file)
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -729,6 +729,7 @@ static void xhci_clear_command_ring(struct xhci_hcd *xhci)
        ring->enq_seg = ring->deq_seg;
        ring->enqueue = ring->dequeue;
 
+       ring->num_trbs_free = ring->num_segs * (TRBS_PER_SEGMENT - 1) - 1;
        /*
         * Ring is now zeroed, so the HW should look for change of ownership
         * when the cycle bit is set to 1.

diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 2337a8e..ea8fc23 100644 (file)
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1278,6 +1278,8 @@ struct xhci_ring {
        u32                     cycle_state;
        unsigned int            stream_id;
        unsigned int            num_segs;
+       unsigned int            num_trbs_free;
+       unsigned int            num_trbs_free_temp;
        enum xhci_ring_type     type;
        bool                    last_td_was_short;
 };