[PATCH] USB: ehci-hcd, scheduler handles TT collisions (3/3)

[USB] ehci-hcd detects microframe transaction scheduling collisions

This detects TT schedule collisions for split periodic transactions
on USB 2.0 hubs, handling both isochronous and interrupt transfers
but not supporting the "wrap around to the next frame" modes for
either transfer type.

The ISO scheduler is modified to use that support for full speed
transfers ... though nothing will yet ask it to do that.

It also tracks schedule depth, to help avoid accepting ISO URBs
which need more time than currently remains unscheduled.

drivers/usb/host/ehci-sched.c

@@ -169,6 +169,93 @@ periodic_usecs (struct ehci_hcd *ehci, unsigned frame, unsigned uframe)
 
 /*-------------------------------------------------------------------------*/
 
+static int same_tt (struct usb_device *dev1, struct usb_device *dev2)
+{
+	if (!dev1->tt || !dev2->tt)
+		return 0;
+	if (dev1->tt != dev2->tt)
+		return 0;
+	if (dev1->tt->multi)
+		return dev1->ttport == dev2->ttport;
+	else
+		return 1;
+}
+
+/* return true iff the device's transaction translator is available
+ * for a periodic transfer starting at the specified frame, using
+ * all the uframes in the mask.
+ */
+static int tt_no_collision (
+	struct ehci_hcd		*ehci,
+	unsigned		period,
+	struct usb_device	*dev,
+	unsigned		frame,
+	u32			uf_mask
+)
+{
+	if (period == 0)	/* error */
+		return 0;
+
+	/* note bandwidth wastage:  split never follows csplit
+	 * (different dev or endpoint) until the next uframe.
+	 * calling convention doesn't make that distinction.
+	 */
+	for (; frame < ehci->periodic_size; frame += period) {
+		union ehci_shadow	here;
+		u32			type;
+
+		here = ehci->pshadow [frame];
+		type = Q_NEXT_TYPE (ehci->periodic [frame]);
+		while (here.ptr) {
+			switch (type) {
+			case Q_TYPE_ITD:
+				type = Q_NEXT_TYPE (here.itd->hw_next);
+				here = here.itd->itd_next;
+				continue;
+			case Q_TYPE_QH:
+				if (same_tt (dev, here.qh->dev)) {
+					u32		mask;
+
+					mask = le32_to_cpu (here.qh->hw_info2);
+					/* "knows" no gap is needed */
+					mask |= mask >> 8;
+					if (mask & uf_mask)
+						break;
+				}
+				type = Q_NEXT_TYPE (here.qh->hw_next);
+				here = here.qh->qh_next;
+				continue;
+			case Q_TYPE_SITD:
+				if (same_tt (dev, here.itd->urb->dev)) {
+					u16		mask;
+
+					mask = le32_to_cpu (here.sitd->hw_uframe);
+					/* FIXME assumes no gap for IN! */
+					mask |= mask >> 8;
+					if (mask & uf_mask)
+						break;
+				}
+				type = Q_NEXT_TYPE (here.qh->hw_next);
+				here = here.sitd->sitd_next;
+				break;
+			// case Q_TYPE_FSTN:
+			default:
+				ehci_dbg (ehci,
+					"periodic frame %d bogus type %d\n",
+					frame, type);
+			}
+
+			/* collision or error */
+			return 0;
+		}
+	}
+
+	/* no collision */
+	return 1;
+}
+
+/*-------------------------------------------------------------------------*/
+
 static int enable_periodic (struct ehci_hcd *ehci)
 {
 	u32	cmd;
@@ -517,8 +604,10 @@ iso_stream_init (
 	unsigned		interval
 )
 {
+	static const u8 smask_out [] = { 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f };
+
 	u32			buf1;
-	unsigned		epnum, maxp, multi;
+	unsigned		epnum, maxp;
 	int			is_input;
 	long			bandwidth;
 
@@ -536,30 +625,62 @@ iso_stream_init (
 		buf1 = 0;
 	}
 
-	stream->highspeed = 1;
+	/* knows about ITD vs SITD */
+	if (dev->speed == USB_SPEED_HIGH) {
+		unsigned multi = hb_mult(maxp);
+
+		stream->highspeed = 1;
+
+		maxp = max_packet(maxp);
+		buf1 |= maxp;
+		maxp *= multi;
 
-	multi = hb_mult(maxp);
-	maxp = max_packet(maxp);
-	buf1 |= maxp;
-	maxp *= multi;
+		stream->buf0 = cpu_to_le32 ((epnum << 8) | dev->devnum);
+		stream->buf1 = cpu_to_le32 (buf1);
+		stream->buf2 = cpu_to_le32 (multi);
+
+		/* usbfs wants to report the average usecs per frame tied up
+		 * when transfers on this endpoint are scheduled ...
+		 */
+		stream->usecs = HS_USECS_ISO (maxp);
+		bandwidth = stream->usecs * 8;
+		bandwidth /= 1 << (interval - 1);
+
+	} else {
+		u32		addr;
+
+		addr = dev->ttport << 24;
+		addr |= dev->tt->hub->devnum << 16;
+		addr |= epnum << 8;
+		addr |= dev->devnum;
+		stream->usecs = HS_USECS_ISO (maxp);
+		if (is_input) {
+			u32	tmp;
+
+			addr |= 1 << 31;
+			stream->c_usecs = stream->usecs;
+			stream->usecs = HS_USECS_ISO (1);
+			stream->raw_mask = 1;
+
+			/* pessimistic c-mask */
+			tmp = usb_calc_bus_time (USB_SPEED_FULL, 1, 0, maxp)
+					/ (125 * 1000);
+			stream->raw_mask |= 3 << (tmp + 9);
+		} else
+			stream->raw_mask = smask_out [maxp / 188];
+		bandwidth = stream->usecs + stream->c_usecs;
+		bandwidth /= 1 << (interval + 2);
+
+		/* stream->splits gets created from raw_mask later */
+		stream->address = cpu_to_le32 (addr);
+	}
+	stream->bandwidth = bandwidth;
 
 	stream->udev = dev;
 
 	stream->bEndpointAddress = is_input | epnum;
 	stream->interval = interval;
 	stream->maxp = maxp;
-
-	stream->buf0 = cpu_to_le32 ((epnum << 8) | dev->devnum);
-	stream->buf1 = cpu_to_le32 (buf1);
-	stream->buf2 = cpu_to_le32 (multi);
-
-	/* usbfs wants to report the average usecs per frame tied up
-	 * when transfers on this endpoint are scheduled ...
-	 */
-	stream->usecs = HS_USECS_ISO (maxp);
-	bandwidth = stream->usecs * 8;
-	bandwidth /= 1 << (interval - 1);
-	stream->bandwidth = bandwidth;
 }
 
 static void
@@ -781,6 +902,98 @@ itd_urb_transaction (
 	return 0;
 }
 
+/*-------------------------------------------------------------------------*/
+
+static inline int
+itd_slot_ok (
+	struct ehci_hcd		*ehci,
+	u32			mod,
+	u32			uframe,
+	u32			end,
+	u8			usecs,
+	u32			period
+)
+{
+	do {
+		/* can't commit more than 80% periodic == 100 usec */
+		if (periodic_usecs (ehci, uframe >> 3, uframe & 0x7)
+				> (100 - usecs))
+			return 0;
+
+		/* we know urb->interval is 2^N uframes */
+		uframe += period;
+		uframe %= mod;
+	} while (uframe != end);
+	return 1;
+}
+
+static inline int
+sitd_slot_ok (
+	struct ehci_hcd		*ehci,
+	u32			mod,
+	struct ehci_iso_stream	*stream,
+	u32			uframe,
+	u32			end,
+	struct ehci_iso_sched	*sched,
+	u32			period_uframes
+)
+{
+	u32			mask, tmp;
+	u32			frame, uf;
+
+	mask = stream->raw_mask << (uframe & 7);
+
+	/* for IN, don't wrap CSPLIT into the next frame */
+	if (mask & ~0xffff)
+		return 0;
+
+	/* this multi-pass logic is simple, but performance may
+	 * suffer when the schedule data isn't cached.
+	 */
+
+	/* check bandwidth */
+	do {
+		u32		max_used;
+
+		frame = uframe >> 3;
+		uf = uframe & 7;
+
+		/* check starts (OUT uses more than one) */
+		max_used = 100 - stream->usecs;
+		for (tmp = stream->raw_mask & 0xff; tmp; tmp >>= 1, uf++) {
+			if (periodic_usecs (ehci, frame, uf) > max_used)
+				return 0;
+		}
+
+		/* for IN, check CSPLIT */
+		if (stream->c_usecs) {
+			max_used = 100 - stream->c_usecs;
+			do {
+				/* tt is busy in the gap before CSPLIT */
+				tmp = 1 << uf;
+				mask |= tmp;
+				tmp <<= 8;
+				if (stream->raw_mask & tmp)
+					break;
+			} while (++uf < 8);
+			if (periodic_usecs (ehci, frame, uf) > max_used)
+				return 0;
+		}
+
+		/* we know urb->interval is 2^N uframes */
+		uframe += period_uframes;
+		uframe %= mod;
+	} while (uframe != end);
+
+	/* tt must be idle for start(s), any gap, and csplit */
+	if (!tt_no_collision (ehci, period_uframes, stream->udev, frame, mask))
+		return 0;
+
+	stream->splits = stream->raw_mask << (uframe & 7);
+	cpu_to_le32s (&stream->splits);
+	return 1;
+}
+
 /*
  * This scheduler plans almost as far into the future as it has actual
  * periodic schedule slots.  (Affected by TUNE_FLS, which defaults to
@@ -795,23 +1008,30 @@ itd_urb_transaction (
 #define SCHEDULE_SLOP	10	/* frames */
 
 static int
-itd_stream_schedule (
+iso_stream_schedule (
 	struct ehci_hcd		*ehci,
 	struct urb		*urb,
 	struct ehci_iso_stream	*stream
 )
 {
-	u32			now, start, end, max;
+	u32			now, start, end, max, period;
 	int			status;
 	unsigned		mod = ehci->periodic_size << 3;
 	struct ehci_iso_sched	*sched = urb->hcpriv;
 
-	if (unlikely (sched->span > (mod - 8 * SCHEDULE_SLOP))) {
+	if (sched->span > (mod - 8 * SCHEDULE_SLOP)) {
 		ehci_dbg (ehci, "iso request %p too long\n", urb);
 		status = -EFBIG;
 		goto fail;
 	}
 
+	if ((stream->depth + sched->span) > mod) {
+		ehci_dbg (ehci, "request %p would overflow (%d+%d>%d)\n",
+			urb, stream->depth, sched->span, mod);
+		status = -EFBIG;
+		goto fail;
+	}
+
 	now = readl (&ehci->regs->frame_index) % mod;
 
 	/* when's the last uframe this urb could start? */
@@ -823,18 +1043,12 @@ itd_stream_schedule (
 	 * and no gaps from host falling behind (irq delays etc)
 	 */
 	if (likely (!list_empty (&stream->td_list))) {
-
 		start = stream->next_uframe;
 		if (start < now)
 			start += mod;
 		if (likely (start < max))
 			goto ready;
-
-		/* two cases:
-		 * (a) we missed some uframes ... can reschedule
-		 * (b) trying to overcommit the schedule
-		 * FIXME (b) should be a hard failure
-		 */
+		/* else fell behind; try to reschedule */
 	}
 
 	/* need to schedule; when's the next (u)frame we could start?
@@ -844,42 +1058,36 @@ itd_stream_schedule (
 	 * jump until after the queue is primed.
 	 */
 	start = SCHEDULE_SLOP * 8 + (now & ~0x07);
+	start %= mod;
 	end = start;
 
-	ehci_vdbg (ehci, "%s schedule from %d (%d..%d), was %d\n",
-			__FUNCTION__, now, start, max,
-			stream->next_uframe);
-
 	/* NOTE:  assumes URB_ISO_ASAP, to limit complexity/bugs */
 
-	if (likely (max > (start + urb->interval)))
-		max = start + urb->interval;
+	period = urb->interval;
+	if (!stream->highspeed)
+		period <<= 3;
+	if (max > (start + period))
+		max = start + period;
 
 	/* hack:  account for itds already scheduled to this endpoint */
-	if (unlikely (list_empty (&stream->td_list)))
+	if (list_empty (&stream->td_list))
 		end = max;
 
 	/* within [start..max] find a uframe slot with enough bandwidth */
 	end %= mod;
 	do {
-		unsigned	uframe;
-		int		enough_space = 1;
+		int		enough_space;
 
 		/* check schedule: enough space? */
-		uframe = start;
-		do {
-			uframe %= mod;
-
-			/* can't commit more than 80% periodic == 100 usec */
-			if (periodic_usecs (ehci, uframe >> 3, uframe & 0x7)
-					> (100 - stream->usecs)) {
-				enough_space = 0;
-				break;
-			}
-
-			/* we know urb->interval is 2^N uframes */
-			uframe += urb->interval;
-		} while (uframe != end);
+		if (stream->highspeed)
+			enough_space = itd_slot_ok (ehci, mod, start, end,
+					stream->usecs, period);
+		else {
+			if ((start % 8) >= 6)
+				continue;
+			enough_space = sitd_slot_ok (ehci, mod, stream,
+					start, end, sched, period);
+		}
 
 		/* (re)schedule it here if there's enough bandwidth */
 		if (enough_space) {
@@ -1035,6 +1243,7 @@ itd_link_urb (
 		first = 0;
 
 		next_uframe += stream->interval;
+		stream->depth += stream->interval;
 		next_uframe %= mod;
 		packet++;
 
@@ -1081,6 +1290,7 @@ itd_complete (
 
 		t = le32_to_cpup (&itd->hw_transaction [uframe]);
 		itd->hw_transaction [uframe] = 0;
+		stream->depth -= stream->interval;
 
 		/* report transfer status */
 		if (unlikely (t & ISO_ERRS)) {
@@ -1183,7 +1393,7 @@ static int itd_submit (struct ehci_hcd *ehci, struct urb *urb, int mem_flags)
 
 	/* schedule ... need to lock */
 	spin_lock_irqsave (&ehci->lock, flags);
-	status = itd_stream_schedule (ehci, urb, stream);
+	status = iso_stream_schedule (ehci, urb, stream);
  	if (likely (status == 0))
 		itd_link_urb (ehci, urb, ehci->periodic_size << 3, stream);
 	spin_unlock_irqrestore (&ehci->lock, flags);

drivers/usb/host/ehci.h

@@ -418,6 +418,7 @@ struct ehci_iso_stream {
 	u32			refcount;
 	u8			bEndpointAddress;
 	u8			highspeed;
+	u16			depth;		/* depth in uframes */
 	struct list_head	td_list;	/* queued itds/sitds */
 	struct list_head	free_list;	/* list of unused itds/sitds */
 	struct usb_device	*udev;
@@ -426,6 +427,7 @@ struct ehci_iso_stream {
 	unsigned long		start;		/* jiffies */
 	unsigned long		rescheduled;
 	int			next_uframe;
+	u32			splits;
 
 	/* the rest is derived from the endpoint descriptor,
 	 * trusting urb->interval == f(epdesc->bInterval) and
@@ -434,6 +436,7 @@ struct ehci_iso_stream {
 	u8			interval;
 	u8			usecs, c_usecs;
 	u16			maxp;
+	u16			raw_mask;
 	unsigned		bandwidth;
 
 	/* This is used to initialize iTD's hw_bufp fields */
@@ -441,7 +444,8 @@ struct ehci_iso_stream {
 	u32			buf1;		
 	u32			buf2;
 
-	/* ... sITD won't use buf[012], and needs TT access ... */
+	/* this is used to initialize sITD's tt info */
+	u32			address;
 };
 
 /*-------------------------------------------------------------------------*/