USB: EHCI: create per-TT bandwidth tables

This patch continues the scheduling changes in ehci-hcd by adding a
table to store the bandwidth allocation below each TT.  This will
speed up the scheduling code, as it will no longer need to read
through the entire schedule to compute the bandwidth currently in use.

Properly speaking, the FS/LS budget calculations should be done in
terms of full-speed bytes per microframe, as described in the USB-2
spec.  However the driver currently uses microseconds per microframe,
and the scheduling code isn't robust enough at this point to change
over.  For the time being, we leave the calculations as they are.

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

4 files changed, 312 insertions, 85 deletions

diff --git a/drivers/usb/host/ehci-dbg.c b/drivers/usb/host/ehci-dbg.c
index 5bbfb1f9929..4a9c2edbcb2 100644
--- a/drivers/usb/host/ehci-dbg.c
+++ b/drivers/usb/host/ehci-dbg.c
@@ -536,10 +536,14 @@ static ssize_t fill_async_buffer(struct debug_buffer *buf)
 static ssize_t fill_bandwidth_buffer(struct debug_buffer *buf)
 {
 	struct ehci_hcd		*ehci;
+	struct ehci_tt		*tt;
+	struct ehci_per_sched	*ps;
 	unsigned		temp, size;
 	char			*next;
 	unsigned		i;
 	u8			*bw;
+	u16			*bf;
+	u8			budget[EHCI_BANDWIDTH_SIZE];
 
 	ehci = hcd_to_ehci(bus_to_hcd(buf->bus));
 	next = buf->output_buf;
@@ -563,6 +567,50 @@ static ssize_t fill_bandwidth_buffer(struct debug_buffer *buf)
 		size -= temp;
 		next += temp;
 	}
+
+	/* Dump all the FS/LS tables */
+	list_for_each_entry(tt, &ehci->tt_list, tt_list) {
+		temp = scnprintf(next, size,
+				"\nTT %s port %d  FS/LS bandwidth allocation (us per frame)\n",
+				dev_name(&tt->usb_tt->hub->dev),
+				tt->tt_port + !!tt->usb_tt->multi);
+		size -= temp;
+		next += temp;
+
+		bf = tt->bandwidth;
+		temp = scnprintf(next, size,
+				"  %5u%5u%5u%5u%5u%5u%5u%5u\n",
+				bf[0], bf[1], bf[2], bf[3],
+					bf[4], bf[5], bf[6], bf[7]);
+		size -= temp;
+		next += temp;
+
+		temp = scnprintf(next, size,
+				"FS/LS budget (us per microframe)\n");
+		size -= temp;
+		next += temp;
+		compute_tt_budget(budget, tt);
+		for (i = 0; i < EHCI_BANDWIDTH_SIZE; i += 8) {
+			bw = &budget[i];
+			temp = scnprintf(next, size,
+					"%2u: %4u%4u%4u%4u%4u%4u%4u%4u\n",
+					i, bw[0], bw[1], bw[2], bw[3],
+						bw[4], bw[5], bw[6], bw[7]);
+			size -= temp;
+			next += temp;
+		}
+		list_for_each_entry(ps, &tt->ps_list, ps_list) {
+			temp = scnprintf(next, size,
+					"%s ep %02x:  %4u @ %2u.%u+%u mask %04x\n",
+					dev_name(&ps->udev->dev),
+					ps->ep->desc.bEndpointAddress,
+					ps->tt_usecs,
+					ps->bw_phase, ps->phase_uf,
+					ps->bw_period, ps->cs_mask);
+			size -= temp;
+			next += temp;
+		}
+	}
 	spin_unlock_irq(&ehci->lock);
 
 	return next - buf->output_buf;
diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 398e8fa3032..e66706aa9f0 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -110,6 +110,9 @@ MODULE_PARM_DESC (ignore_oc, "ignore bogus hardware overcurrent indications");
 #include "ehci.h"
 #include "pci-quirks.h"
 
+static void compute_tt_budget(u8 budget_table[EHCI_BANDWIDTH_SIZE],
+		struct ehci_tt *tt);
+
 /*
  * The MosChip MCS9990 controller updates its microframe counter
  * a little before the frame counter, and occasionally we will read
@@ -484,6 +487,7 @@ static int ehci_init(struct usb_hcd *hcd)
 	INIT_LIST_HEAD(&ehci->intr_qh_list);
 	INIT_LIST_HEAD(&ehci->cached_itd_list);
 	INIT_LIST_HEAD(&ehci->cached_sitd_list);
+	INIT_LIST_HEAD(&ehci->tt_list);
 
 	if (HCC_PGM_FRAMELISTLEN(hcc_params)) {
 		/* periodic schedule size can be smaller than default */
@@ -1051,6 +1055,19 @@ static int ehci_get_frame (struct usb_hcd *hcd)
 
 /*-------------------------------------------------------------------------*/
 
+/* Device addition and removal */
+
+static void ehci_remove_device(struct usb_hcd *hcd, struct usb_device *udev)
+{
+	struct ehci_hcd		*ehci = hcd_to_ehci(hcd);
+
+	spin_lock_irq(&ehci->lock);
+	drop_tt(udev);
+	spin_unlock_irq(&ehci->lock);
+}
+
+/*-------------------------------------------------------------------------*/
+
 #ifdef	CONFIG_PM
 
 /* suspend/resume, section 4.3 */
@@ -1194,6 +1211,11 @@ static const struct hc_driver ehci_hc_driver = {
 	.bus_resume =		ehci_bus_resume,
 	.relinquish_port =	ehci_relinquish_port,
 	.port_handed_over =	ehci_port_handed_over,
+
+	/*
+	 * device support
+	 */
+	.free_dev =		ehci_remove_device,
 };
 
 void ehci_init_driver(struct hc_driver *drv,
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 790a64c0da5..b5f957d322e 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -106,6 +106,103 @@ static void periodic_unlink (struct ehci_hcd *ehci, unsigned frame, void *ptr)
 		*hw_p = ehci->dummy->qh_dma;
 }
 
+/*-------------------------------------------------------------------------*/
+
+/* Bandwidth and TT management */
+
+/* Find the TT data structure for this device; create it if necessary */
+static struct ehci_tt *find_tt(struct usb_device *udev)
+{
+	struct usb_tt		*utt = udev->tt;
+	struct ehci_tt		*tt, **tt_index, **ptt;
+	unsigned		port;
+	bool			allocated_index = false;
+
+	if (!utt)
+		return NULL;		/* Not below a TT */
+
+	/*
+	 * Find/create our data structure.
+	 * For hubs with a single TT, we get it directly.
+	 * For hubs with multiple TTs, there's an extra level of pointers.
+	 */
+	tt_index = NULL;
+	if (utt->multi) {
+		tt_index = utt->hcpriv;
+		if (!tt_index) {		/* Create the index array */
+			tt_index = kzalloc(utt->hub->maxchild *
+					sizeof(*tt_index), GFP_ATOMIC);
+			if (!tt_index)
+				return ERR_PTR(-ENOMEM);
+			utt->hcpriv = tt_index;
+			allocated_index = true;
+		}
+		port = udev->ttport - 1;
+		ptt = &tt_index[port];
+	} else {
+		port = 0;
+		ptt = (struct ehci_tt **) &utt->hcpriv;
+	}
+
+	tt = *ptt;
+	if (!tt) {				/* Create the ehci_tt */
+		struct ehci_hcd		*ehci =
+				hcd_to_ehci(bus_to_hcd(udev->bus));
+
+		tt = kzalloc(sizeof(*tt), GFP_ATOMIC);
+		if (!tt) {
+			if (allocated_index) {
+				utt->hcpriv = NULL;
+				kfree(tt_index);
+			}
+			return ERR_PTR(-ENOMEM);
+		}
+		list_add_tail(&tt->tt_list, &ehci->tt_list);
+		INIT_LIST_HEAD(&tt->ps_list);
+		tt->usb_tt = utt;
+		tt->tt_port = port;
+		*ptt = tt;
+	}
+
+	return tt;
+}
+
+/* Release the TT above udev, if it's not in use */
+static void drop_tt(struct usb_device *udev)
+{
+	struct usb_tt		*utt = udev->tt;
+	struct ehci_tt		*tt, **tt_index, **ptt;
+	int			cnt, i;
+
+	if (!utt || !utt->hcpriv)
+		return;		/* Not below a TT, or never allocated */
+
+	cnt = 0;
+	if (utt->multi) {
+		tt_index = utt->hcpriv;
+		ptt = &tt_index[udev->ttport - 1];
+
+		/* How many entries are left in tt_index? */
+		for (i = 0; i < utt->hub->maxchild; ++i)
+			cnt += !!tt_index[i];
+	} else {
+		tt_index = NULL;
+		ptt = (struct ehci_tt **) &utt->hcpriv;
+	}
+
+	tt = *ptt;
+	if (!tt || !list_empty(&tt->ps_list))
+		return;		/* never allocated, or still in use */
+
+	list_del(&tt->tt_list);
+	*ptt = NULL;
+	kfree(tt);
+	if (cnt == 1) {
+		utt->hcpriv = NULL;
+		kfree(tt_index);
+	}
+}
+
 static void bandwidth_dbg(struct ehci_hcd *ehci, int sign, char *type,
 		struct ehci_per_sched *ps)
 {
@@ -125,6 +222,8 @@ static void reserve_release_intr_bandwidth(struct ehci_hcd *ehci,
 	unsigned		i, j, m;
 	int			usecs = qh->ps.usecs;
 	int			c_usecs = qh->ps.c_usecs;
+	int			tt_usecs = qh->ps.tt_usecs;
+	struct ehci_tt		*tt;
 
 	if (qh->ps.phase == NO_FRAME)	/* Bandwidth wasn't reserved */
 		return;
@@ -135,6 +234,7 @@ static void reserve_release_intr_bandwidth(struct ehci_hcd *ehci,
 	if (sign < 0) {		/* Release bandwidth */
 		usecs = -usecs;
 		c_usecs = -c_usecs;
+		tt_usecs = -tt_usecs;
 	}
 
 	/* Entire transaction (high speed) or start-split (full/low speed) */
@@ -153,11 +253,60 @@ static void reserve_release_intr_bandwidth(struct ehci_hcd *ehci,
 			}
 		}
 	}
+
+	/* FS/LS bus bandwidth */
+	if (tt_usecs) {
+		tt = find_tt(qh->ps.udev);
+		if (sign > 0)
+			list_add_tail(&qh->ps.ps_list, &tt->ps_list);
+		else
+			list_del(&qh->ps.ps_list);
+
+		for (i = start_uf >> 3; i < EHCI_BANDWIDTH_FRAMES;
+				i += qh->ps.bw_period)
+			tt->bandwidth[i] += tt_usecs;
+	}
 }
 
 /*-------------------------------------------------------------------------*/
 
-static int same_tt (struct usb_device *dev1, struct usb_device *dev2)
+static void compute_tt_budget(u8 budget_table[EHCI_BANDWIDTH_SIZE],
+		struct ehci_tt *tt)
+{
+	struct ehci_per_sched	*ps;
+	unsigned		uframe, uf, x;
+	u8			*budget_line;
+
+	if (!tt)
+		return;
+	memset(budget_table, 0, EHCI_BANDWIDTH_SIZE);
+
+	/* Add up the contributions from all the endpoints using this TT */
+	list_for_each_entry(ps, &tt->ps_list, ps_list) {
+		for (uframe = ps->bw_phase << 3; uframe < EHCI_BANDWIDTH_SIZE;
+				uframe += ps->bw_uperiod) {
+			budget_line = &budget_table[uframe];
+			x = ps->tt_usecs;
+
+			/* propagate the time forward */
+			for (uf = ps->phase_uf; uf < 8; ++uf) {
+				x += budget_line[uf];
+
+				/* Each microframe lasts 125 us */
+				if (x <= 125) {
+					budget_line[uf] = x;
+					break;
+				} else {
+					budget_line[uf] = 125;
+					x -= 125;
+				}
+			}
+		}
+	}
+}
+
+static int __maybe_unused same_tt(struct usb_device *dev1,
+		struct usb_device *dev2)
 {
 	if (!dev1->tt || !dev2->tt)
 		return 0;
@@ -205,68 +354,6 @@ static inline void carryover_tt_bandwidth(unsigned short tt_usecs[8])
 	}
 }
 
-/* How many of the tt's periodic downstream 1000 usecs are allocated?
- *
- * While this measures the bandwidth in terms of usecs/uframe,
- * the low/fullspeed bus has no notion of uframes, so any particular
- * low/fullspeed transfer can "carry over" from one uframe to the next,
- * since the TT just performs downstream transfers in sequence.
- *
- * For example two separate 100 usec transfers can start in the same uframe,
- * and the second one would "carry over" 75 usecs into the next uframe.
- */
-static void
-periodic_tt_usecs (
-	struct ehci_hcd *ehci,
-	struct usb_device *dev,
-	unsigned frame,
-	unsigned short tt_usecs[8]
-)
-{
-	__hc32			*hw_p = &ehci->periodic [frame];
-	union ehci_shadow	*q = &ehci->pshadow [frame];
-	unsigned char		uf;
-
-	memset(tt_usecs, 0, 16);
-
-	while (q->ptr) {
-		switch (hc32_to_cpu(ehci, Q_NEXT_TYPE(ehci, *hw_p))) {
-		case Q_TYPE_ITD:
-			hw_p = &q->itd->hw_next;
-			q = &q->itd->itd_next;
-			continue;
-		case Q_TYPE_QH:
-			if (same_tt(dev, q->qh->ps.udev)) {
-				uf = tt_start_uframe(ehci, q->qh->hw->hw_info2);
-				tt_usecs[uf] += q->qh->ps.tt_usecs;
-			}
-			hw_p = &q->qh->hw->hw_next;
-			q = &q->qh->qh_next;
-			continue;
-		case Q_TYPE_SITD:
-			if (same_tt(dev, q->sitd->urb->dev)) {
-				uf = tt_start_uframe(ehci, q->sitd->hw_uframe);
-				tt_usecs[uf] += q->sitd->stream->ps.tt_usecs;
-			}
-			hw_p = &q->sitd->hw_next;
-			q = &q->sitd->sitd_next;
-			continue;
-		// case Q_TYPE_FSTN:
-		default:
-			ehci_dbg(ehci, "ignoring periodic frame %d FSTN\n",
-					frame);
-			hw_p = &q->fstn->hw_next;
-			q = &q->fstn->fstn_next;
-		}
-	}
-
-	carryover_tt_bandwidth(tt_usecs);
-
-	if (max_tt_usecs[7] < tt_usecs[7])
-		ehci_err(ehci, "frame %d tt sched overrun: %d usecs\n",
-			frame, tt_usecs[7] - max_tt_usecs[7]);
-}
-
 /*
  * Return true if the device's tt's downstream bus is available for a
  * periodic transfer of the specified length (usecs), starting at the
@@ -290,20 +377,29 @@ periodic_tt_usecs (
  */
 static int tt_available (
 	struct ehci_hcd		*ehci,
-	unsigned		period,
-	struct usb_device	*dev,
+	struct ehci_per_sched	*ps,
+	struct ehci_tt		*tt,
 	unsigned		frame,
-	unsigned		uframe,
-	u16			usecs
+	unsigned		uframe
 )
 {
+	unsigned		period = ps->bw_period;
+	unsigned		usecs = ps->tt_usecs;
+
 	if ((period == 0) || (uframe >= 7))	/* error */
 		return 0;
 
-	for (; frame < ehci->periodic_size; frame += period) {
-		unsigned short tt_usecs[8];
+	for (frame &= period - 1; frame < EHCI_BANDWIDTH_FRAMES;
+			frame += period) {
+		unsigned	i, uf;
+		unsigned short	tt_usecs[8];
+
+		if (tt->bandwidth[frame] + usecs > 900)
+			return 0;
 
-		periodic_tt_usecs (ehci, dev, frame, tt_usecs);
+		uf = frame << 3;
+		for (i = 0; i < 8; (++i, ++uf))
+			tt_usecs[i] = ehci->tt_budget[uf];
 
 		if (max_tt_usecs[uframe] <= tt_usecs[uframe])
 			return 0;
@@ -315,7 +411,7 @@ static int tt_available (
 		 */
 		if (125 < usecs) {
 			int ufs = (usecs / 125);
-			int i;
+
 			for (i = uframe; i < (uframe + ufs) && i < 8; i++)
 				if (0 < tt_usecs[i])
 					return 0;
@@ -697,8 +793,9 @@ static int check_intr_schedule (
 	struct ehci_hcd		*ehci,
 	unsigned		frame,
 	unsigned		uframe,
-	const struct ehci_qh	*qh,
-	__hc32			*c_maskp
+	struct ehci_qh		*qh,
+	__hc32			*c_maskp,
+	struct ehci_tt		*tt
 )
 {
 	int		retval = -ENOSPC;
@@ -716,8 +813,7 @@ static int check_intr_schedule (
 	}
 
 #ifdef CONFIG_USB_EHCI_TT_NEWSCHED
-	if (tt_available(ehci, qh->ps.bw_period, qh->ps.udev, frame, uframe,
-				qh->ps.tt_usecs)) {
+	if (tt_available(ehci, &qh->ps, tt, frame, uframe)) {
 		unsigned i;
 
 		/* TODO : this may need FSTN for SSPLIT in uframe 5. */
@@ -763,10 +859,11 @@ done:
  */
 static int qh_schedule(struct ehci_hcd *ehci, struct ehci_qh *qh)
 {
-	int		status;
+	int		status = 0;
 	unsigned	uframe;
 	unsigned	c_mask;
 	struct ehci_qh_hw	*hw = qh->hw;
+	struct ehci_tt		*tt;
 
 	hw->hw_next = EHCI_LIST_END(ehci);
 
@@ -778,7 +875,12 @@ static int qh_schedule(struct ehci_hcd *ehci, struct ehci_qh *qh)
 
 	uframe = 0;
 	c_mask = 0;
-	status = -ENOSPC;
+	tt = find_tt(qh->ps.udev);
+	if (IS_ERR(tt)) {
+		status = PTR_ERR(tt);
+		goto done;
+	}
+	compute_tt_budget(ehci->tt_budget, tt);
 
 	/* else scan the schedule to find a group of slots such that all
 	 * uframes have enough periodic bandwidth available.
@@ -788,22 +890,24 @@ static int qh_schedule(struct ehci_hcd *ehci, struct ehci_qh *qh)
 		int		i;
 		unsigned	frame;
 
-		for (i = qh->ps.bw_period; status && i > 0; --i) {
+		for (i = qh->ps.bw_period; i > 0; --i) {
 			frame = ++ehci->random_frame & (qh->ps.bw_period - 1);
 			for (uframe = 0; uframe < 8; uframe++) {
 				status = check_intr_schedule(ehci,
-						frame, uframe, qh, &c_mask);
+						frame, uframe, qh, &c_mask, tt);
 				if (status == 0)
-					break;
+					goto got_it;
 			}
 		}
 
 	/* qh->ps.bw_period == 0 means every uframe */
 	} else {
-		status = check_intr_schedule(ehci, 0, 0, qh, &c_mask);
+		status = check_intr_schedule(ehci, 0, 0, qh, &c_mask, tt);
 	}
 	if (status)
 		goto done;
+
+ got_it:
 	qh->ps.phase = (qh->ps.period ? ehci->random_frame &
 			(qh->ps.period - 1) : 0);
 	qh->ps.bw_phase = qh->ps.phase & (qh->ps.bw_period - 1);
@@ -1232,6 +1336,8 @@ static void reserve_release_iso_bandwidth(struct ehci_hcd *ehci,
 	unsigned		s_mask, c_mask, m;
 	int			usecs = stream->ps.usecs;
 	int			c_usecs = stream->ps.c_usecs;
+	int			tt_usecs = stream->ps.tt_usecs;
+	struct ehci_tt		*tt;
 
 	if (stream->ps.phase == NO_FRAME)	/* Bandwidth wasn't reserved */
 		return;
@@ -1242,6 +1348,7 @@ static void reserve_release_iso_bandwidth(struct ehci_hcd *ehci,
 	if (sign < 0) {		/* Release bandwidth */
 		usecs = -usecs;
 		c_usecs = -c_usecs;
+		tt_usecs = -tt_usecs;
 	}
 
 	if (!stream->splits) {		/* High speed */
@@ -1264,6 +1371,16 @@ static void reserve_release_iso_bandwidth(struct ehci_hcd *ehci,
 					ehci->bandwidth[i+j] += c_usecs;
 			}
 		}
+
+		tt = find_tt(stream->ps.udev);
+		if (sign > 0)
+			list_add_tail(&stream->ps.ps_list, &tt->ps_list);
+		else
+			list_del(&stream->ps.ps_list);
+
+		for (i = uframe >> 3; i < EHCI_BANDWIDTH_FRAMES;
+				i += stream->ps.bw_period)
+			tt->bandwidth[i] += tt_usecs;
 	}
 }
 
@@ -1292,7 +1409,8 @@ sitd_slot_ok (
 	struct ehci_hcd		*ehci,
 	struct ehci_iso_stream	*stream,
 	unsigned		uframe,
-	struct ehci_iso_sched	*sched
+	struct ehci_iso_sched	*sched,
+	struct ehci_tt		*tt
 )
 {
 	unsigned		mask, tmp;
@@ -1317,8 +1435,7 @@ sitd_slot_ok (
 	 * tt_available scheduling guarantees 10+% for control/bulk.
 	 */
 	uf = uframe & 7;
-	if (!tt_available(ehci, stream->ps.bw_period,
-			stream->ps.udev, frame, uf, stream->ps.tt_usecs))
+	if (!tt_available(ehci, &stream->ps, tt, frame, uf))
 		return 0;
 #else
 	/* tt must be idle for start(s), any gap, and csplit.
@@ -1417,6 +1534,13 @@ iso_stream_schedule (
 		/* Schedule the endpoint */
 		if (stream->ps.phase == NO_FRAME) {
 			int		done = 0;
+			struct ehci_tt	*tt = find_tt(stream->ps.udev);
+
+			if (IS_ERR(tt)) {
+				status = PTR_ERR(tt);
+				goto fail;
+			}
+			compute_tt_budget(ehci->tt_budget, tt);
 
 			start = (now & ~0x07) + SCHEDULING_DELAY;
 
@@ -1437,7 +1561,7 @@ iso_stream_schedule (
 					if ((start % 8) >= 6)
 						continue;
 					if (sitd_slot_ok(ehci, stream, start,
-							sched))
+							sched, tt))
 						done = 1;
 				}
 			} while (start > next && !done);
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index 12504fbded5..e8f41c5e771 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -61,6 +61,7 @@ struct ehci_stats {
 struct ehci_per_sched {
 	struct usb_device	*udev;		/* access to the TT */
 	struct usb_host_endpoint *ep;
+	struct list_head	ps_list;	/* node on ehci_tt's ps_list */
 	u16			tt_usecs;	/* time on the FS/LS bus */
 	u16			cs_mask;	/* C-mask and S-mask bytes */
 	u16			period;		/* actual period in frames */
@@ -256,6 +257,9 @@ struct ehci_hcd {			/* one per controller */
 #define EHCI_BANDWIDTH_FRAMES	(EHCI_BANDWIDTH_SIZE >> 3)
 	u8			bandwidth[EHCI_BANDWIDTH_SIZE];
 						/* us allocated per uframe */
+	u8			tt_budget[EHCI_BANDWIDTH_SIZE];
+						/* us budgeted per uframe */
+	struct list_head	tt_list;
 
 	/* platform-specific data -- must come last */
 	unsigned long		priv[0] __aligned(sizeof(s64));
@@ -595,6 +599,35 @@ struct ehci_fstn {
 
 /*-------------------------------------------------------------------------*/
 
+/*
+ * USB-2.0 Specification Sections 11.14 and 11.18
+ * Scheduling and budgeting split transactions using TTs
+ *
+ * A hub can have a single TT for all its ports, or multiple TTs (one for each
+ * port).  The bandwidth and budgeting information for the full/low-speed bus
+ * below each TT is self-contained and independent of the other TTs or the
+ * high-speed bus.
+ *
+ * "Bandwidth" refers to the number of microseconds on the FS/LS bus allocated
+ * to an interrupt or isochronous endpoint for each frame.  "Budget" refers to
+ * the best-case estimate of the number of full-speed bytes allocated to an
+ * endpoint for each microframe within an allocated frame.
+ *
+ * Removal of an endpoint invalidates a TT's budget.  Instead of trying to
+ * keep an up-to-date record, we recompute the budget when it is needed.
+ */
+
+struct ehci_tt {
+	u16			bandwidth[EHCI_BANDWIDTH_FRAMES];
+
+	struct list_head	tt_list;	/* List of all ehci_tt's */
+	struct list_head	ps_list;	/* Items using this TT */
+	struct usb_tt		*usb_tt;
+	int			tt_port;	/* TT port number */
+};
+
+/*-------------------------------------------------------------------------*/
+
 /* Prepare the PORTSC wakeup flags during controller suspend/resume */
 
 #define ehci_prepare_ports_for_controller_suspend(ehci, do_wakeup)	\