UHCI: Eliminate asynchronous skeleton Queue Headers

This patch (as856) attempts to improve the performance of uhci-hcd by
removing the asynchronous skeleton Queue Headers.  They don't contain
any useful information but the controller has to read through them at
least once every millisecond, incurring a non-zero DMA overhead.

Now all the asynchronous queues are combined, along with the period-1
interrupt queue, into a single list with a single skeleton QH.  The
start of the low-speed control, full-speed control, and bulk sublists
is determined by linear search.  Since there should rarely be more
than a couple of QHs in the list, the searches should incur a much
smaller total load than keeping the skeleton QHs.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 171 insertions, 22 deletions

diff --git a/drivers/usb/host/uhci-q.c b/drivers/usb/host/uhci-q.c
index a0c6bf6128a3..f4ebdb3e488f 100644
--- a/drivers/usb/host/uhci-q.c
+++ b/drivers/usb/host/uhci-q.c
@@ -13,7 +13,7 @@
  * (C) Copyright 2000 Yggdrasil Computing, Inc. (port of new PCI interface
  *               support from usb-ohci.c by Adam Richter, adam@yggdrasil.com).
  * (C) Copyright 1999 Gregory P. Smith (from usb-ohci.c)
- * (C) Copyright 2004-2006 Alan Stern, stern@rowland.harvard.edu
+ * (C) Copyright 2004-2007 Alan Stern, stern@rowland.harvard.edu
  */
 
 
@@ -45,14 +45,43 @@ static inline void uhci_clear_next_interrupt(struct uhci_hcd *uhci)
  */
 static void uhci_fsbr_on(struct uhci_hcd *uhci)
 {
+        struct uhci_qh *fsbr_qh, *lqh, *tqh;
+
         uhci->fsbr_is_on = 1;
-        uhci->skel_term_qh->link = LINK_TO_QH(uhci->skel_fs_control_qh);
+        lqh = list_entry(uhci->skel_async_qh->node.prev,
+                        struct uhci_qh, node);
+
+        /* Find the first FSBR QH.  Linear search through the list is
+         * acceptable because normally FSBR gets turned on as soon as
+         * one QH needs it. */
+        fsbr_qh = NULL;
+        list_for_each_entry_reverse(tqh, &uhci->skel_async_qh->node, node) {
+                if (tqh->skel < SKEL_FSBR)
+                        break;
+                fsbr_qh = tqh;
+        }
+
+        /* No FSBR QH means we must insert the terminating skeleton QH */
+        if (!fsbr_qh) {
+                uhci->skel_term_qh->link = LINK_TO_QH(uhci->skel_term_qh);
+                wmb();
+                lqh->link = uhci->skel_term_qh->link;
+
+        /* Otherwise loop the last QH to the first FSBR QH */
+        } else
+                lqh->link = LINK_TO_QH(fsbr_qh);
 }
 
 static void uhci_fsbr_off(struct uhci_hcd *uhci)
 {
+        struct uhci_qh *lqh;
+
         uhci->fsbr_is_on = 0;
-        uhci->skel_term_qh->link = UHCI_PTR_TERM;
+        lqh = list_entry(uhci->skel_async_qh->node.prev,
+                        struct uhci_qh, node);
+
+        /* End the async list normally and unlink the terminating QH */
+        lqh->link = uhci->skel_term_qh->link = UHCI_PTR_TERM;
 }
 
 static void uhci_add_fsbr(struct uhci_hcd *uhci, struct urb *urb)
@@ -404,12 +433,81 @@ static void uhci_fixup_toggles(struct uhci_qh *qh, int skip_first)
 }
 
 /*
- * Put a QH on the schedule in both hardware and software
+ * Link an Isochronous QH into its skeleton's list
  */
-static void uhci_activate_qh(struct uhci_hcd *uhci, struct uhci_qh *qh)
+static inline void link_iso(struct uhci_hcd *uhci, struct uhci_qh *qh)
+{
+        list_add_tail(&qh->node, &uhci->skel_iso_qh->node);
+
+        /* Isochronous QHs aren't linked by the hardware */
+}
+
+/*
+ * Link a high-period interrupt QH into the schedule at the end of its
+ * skeleton's list
+ */
+static void link_interrupt(struct uhci_hcd *uhci, struct uhci_qh *qh)
 {
         struct uhci_qh *pqh;
 
+        list_add_tail(&qh->node, &uhci->skelqh[qh->skel]->node);
+
+        pqh = list_entry(qh->node.prev, struct uhci_qh, node);
+        qh->link = pqh->link;
+        wmb();
+        pqh->link = LINK_TO_QH(qh);
+}
+
+/*
+ * Link a period-1 interrupt or async QH into the schedule at the
+ * correct spot in the async skeleton's list, and update the FSBR link
+ */
+static void link_async(struct uhci_hcd *uhci, struct uhci_qh *qh)
+{
+        struct uhci_qh *pqh, *lqh;
+        __le32 link_to_new_qh;
+        __le32 *extra_link = &link_to_new_qh;
+
+        /* Find the predecessor QH for our new one and insert it in the list.
+         * The list of QHs is expected to be short, so linear search won't
+         * take too long. */
+        list_for_each_entry_reverse(pqh, &uhci->skel_async_qh->node, node) {
+                if (pqh->skel <= qh->skel)
+                        break;
+        }
+        list_add(&qh->node, &pqh->node);
+        qh->link = pqh->link;
+
+        link_to_new_qh = LINK_TO_QH(qh);
+
+        /* If this is now the first FSBR QH, take special action */
+        if (uhci->fsbr_is_on && pqh->skel < SKEL_FSBR &&
+                        qh->skel >= SKEL_FSBR) {
+                lqh = list_entry(uhci->skel_async_qh->node.prev,
+                                struct uhci_qh, node);
+
+                /* If the new QH is also the last one, we must unlink
+                 * the terminating skeleton QH and make the new QH point
+                 * back to itself. */
+                if (qh == lqh) {
+                        qh->link = link_to_new_qh;
+                        extra_link = &uhci->skel_term_qh->link;
+
+                /* Otherwise the last QH must point to the new QH */
+                } else
+                        extra_link = &lqh->link;
+        }
+
+        /* Link it into the schedule */
+        wmb();
+        *extra_link = pqh->link = link_to_new_qh;
+}
+
+/*
+ * Put a QH on the schedule in both hardware and software
+ */
+static void uhci_activate_qh(struct uhci_hcd *uhci, struct uhci_qh *qh)
+{
         WARN_ON(list_empty(&qh->queue));
 
         /* Set the element pointer if it isn't set already.
@@ -431,18 +529,64 @@ static void uhci_activate_qh(struct uhci_hcd *uhci, struct uhci_qh *qh)
                 return;
         qh->state = QH_STATE_ACTIVE;
 
-        /* Move the QH from its old list to the end of the appropriate
+        /* Move the QH from its old list to the correct spot in the appropriate
          * skeleton's list */
         if (qh == uhci->next_qh)
                 uhci->next_qh = list_entry(qh->node.next, struct uhci_qh,
                                 node);
-        list_move_tail(&qh->node, &qh->skel->node);
+        list_del(&qh->node);
+
+        if (qh->skel == SKEL_ISO)
+                link_iso(uhci, qh);
+        else if (qh->skel < SKEL_ASYNC)
+                link_interrupt(uhci, qh);
+        else
+                link_async(uhci, qh);
+}
+
+/*
+ * Unlink a high-period interrupt QH from the schedule
+ */
+static void unlink_interrupt(struct uhci_hcd *uhci, struct uhci_qh *qh)
+{
+        struct uhci_qh *pqh;
 
-        /* Link it into the schedule */
         pqh = list_entry(qh->node.prev, struct uhci_qh, node);
-        qh->link = pqh->link;
-        wmb();
-        pqh->link = LINK_TO_QH(qh);
+        pqh->link = qh->link;
+        mb();
+}
+
+/*
+ * Unlink a period-1 interrupt or async QH from the schedule
+ */
+static void unlink_async(struct uhci_hcd *uhci, struct uhci_qh *qh)
+{
+        struct uhci_qh *pqh, *lqh;
+        __le32 link_to_next_qh = qh->link;
+
+        pqh = list_entry(qh->node.prev, struct uhci_qh, node);
+
+        /* If this is the first FSBQ QH, take special action */
+        if (uhci->fsbr_is_on && pqh->skel < SKEL_FSBR &&
+                        qh->skel >= SKEL_FSBR) {
+                lqh = list_entry(uhci->skel_async_qh->node.prev,
+                                struct uhci_qh, node);
+
+                /* If this QH is also the last one, we must link in
+                 * the terminating skeleton QH. */
+                if (qh == lqh) {
+                        link_to_next_qh = LINK_TO_QH(uhci->skel_term_qh);
+                        uhci->skel_term_qh->link = link_to_next_qh;
+                        wmb();
+                        qh->link = link_to_next_qh;
+
+                /* Otherwise the last QH must point to the new first FSBR QH */
+                } else
+                        lqh->link = link_to_next_qh;
+        }
+
+        pqh->link = link_to_next_qh;
+        mb();
 }
 
 /*
@@ -450,17 +594,18 @@ static void uhci_activate_qh(struct uhci_hcd *uhci, struct uhci_qh *qh)
  */
 static void uhci_unlink_qh(struct uhci_hcd *uhci, struct uhci_qh *qh)
 {
-        struct uhci_qh *pqh;
-
         if (qh->state == QH_STATE_UNLINKING)
                 return;
         WARN_ON(qh->state != QH_STATE_ACTIVE || !qh->udev);
         qh->state = QH_STATE_UNLINKING;
 
         /* Unlink the QH from the schedule and record when we did it */
-        pqh = list_entry(qh->node.prev, struct uhci_qh, node);
-        pqh->link = qh->link;
-        mb();
+        if (qh->skel == SKEL_ISO)
+                ;
+        else if (qh->skel < SKEL_ASYNC)
+                unlink_interrupt(uhci, qh);
+        else
+                unlink_async(uhci, qh);
 
         uhci_get_current_frame_number(uhci);
         qh->unlink_frame = uhci->frame_number;
@@ -696,6 +841,7 @@ static int uhci_submit_control(struct uhci_hcd *uhci, struct urb *urb,
         dma_addr_t data = urb->transfer_dma;
         __le32 *plink;
         struct urb_priv *urbp = urb->hcpriv;
+        int skel;
 
         /* The "pipe" thing contains the destination in bits 8--18 */
         destination = (urb->pipe & PIPE_DEVEP_MASK) | USB_PID_SETUP;
@@ -796,11 +942,13 @@ static int uhci_submit_control(struct uhci_hcd *uhci, struct urb *urb,
          * isn't in the CONFIGURED state. */
         if (urb->dev->speed == USB_SPEED_LOW ||
                         urb->dev->state != USB_STATE_CONFIGURED)
-                qh->skel = uhci->skel_ls_control_qh;
+                skel = SKEL_LS_CONTROL;
         else {
-                qh->skel = uhci->skel_fs_control_qh;
+                skel = SKEL_FS_CONTROL;
                 uhci_add_fsbr(uhci, urb);
         }
+        if (qh->state != QH_STATE_ACTIVE)
+                qh->skel = skel;
 
         urb->actual_length = -8;        /* Account for the SETUP packet */
         return 0;
@@ -930,7 +1078,7 @@ nomem:
         return -ENOMEM;
 }
 
-static inline int uhci_submit_bulk(struct uhci_hcd *uhci, struct urb *urb,
+static int uhci_submit_bulk(struct uhci_hcd *uhci, struct urb *urb,
                 struct uhci_qh *qh)
 {
         int ret;
@@ -939,7 +1087,8 @@ static inline int uhci_submit_bulk(struct uhci_hcd *uhci, struct urb *urb,
         if (urb->dev->speed == USB_SPEED_LOW)
                 return -EINVAL;
 
-        qh->skel = uhci->skel_bulk_qh;
+        if (qh->state != QH_STATE_ACTIVE)
+                qh->skel = SKEL_BULK;
         ret = uhci_submit_common(uhci, urb, qh);
         if (ret == 0)
                 uhci_add_fsbr(uhci, urb);
@@ -967,7 +1116,7 @@ static int uhci_submit_interrupt(struct uhci_hcd *uhci, struct urb *urb,
                 if (exponent < 0)
                         return -EINVAL;
                 qh->period = 1 << exponent;
-                qh->skel = uhci->skelqh[UHCI_SKEL_INDEX(exponent)];
+                qh->skel = SKEL_INDEX(exponent);
 
                 /* For now, interrupt phase is fixed by the layout
                  * of the QH lists. */
@@ -1215,7 +1364,7 @@ static int uhci_submit_isochronous(struct uhci_hcd *uhci, struct urb *urb,
                 qh->iso_status = 0;
         }
 
-        qh->skel = uhci->skel_iso_qh;
+        qh->skel = SKEL_ISO;
         if (!qh->bandwidth_reserved)
                 uhci_reserve_bandwidth(uhci, qh);
         return 0;