ehci-sched.c

linux客户机函数定义的实际例子

				itd = 0;
				break;
			}
			itd = list_entry (itd->itd_list.next,
				struct ehci_itd, itd_list);
		}
		if (!itd)
			continue;
		
		/* that's where we'll schedule this! */
		itd = urb->hcpriv;
		urb->start_frame = start >> 3;
		vdbg ("ISO urb %p (%d packets period %d) starting %d.%d",
			urb, urb->number_of_packets, urb->interval,
			urb->start_frame, start & 0x7);
		for (i = 0, uframe = start, usecs = 0;
				i < urb->number_of_packets;
				i++, uframe += urb->interval) {
			uframe %= mod;

			itd->uframe = uframe;
			itd->hw_transaction [uframe & 0x07] = itd->transaction;
			itd_link (ehci, (uframe >> 3) % ehci->periodic_size,
				itd);
			wmb ();
			usecs += itd->usecs;

			itd = list_entry (itd->itd_list.next,
				struct ehci_itd, itd_list);
		}

		/* update bandwidth utilization records (for usbfs)
		 *
		 * FIXME This claims each URB queued to an endpoint, as if
		 * transfers were concurrent, not sequential.  So bandwidth
		 * typically gets double-billed ... comes from tying it to
		 * URBs rather than endpoints in the schedule.  Luckily we
		 * don't use this usbfs data for serious decision making.
		 */
		usecs /= urb->number_of_packets;
		usecs /= urb->interval;
		usecs >>= 3;
		if (usecs < 1)
			usecs = 1;
		usb_claim_bandwidth (urb->dev, urb, usecs, 1);

		/* maybe enable periodic schedule processing */
		if (!ehci->periodic_urbs++)
			enable_periodic (ehci);

		return 0;

	} while ((start = ++start % mod) != max);

	/* no room in the schedule */
	dbg ("urb %p, CAN'T SCHEDULE", urb);
	return -ENOSPC;
}

/*-------------------------------------------------------------------------*/

#define	ISO_ERRS (EHCI_ISOC_BUF_ERR | EHCI_ISOC_BABBLE | EHCI_ISOC_XACTERR)

static unsigned long
itd_complete (
	struct ehci_hcd	*ehci,
	struct ehci_itd	*itd,
	unsigned	uframe,
	unsigned long	flags
) {
	struct urb				*urb = itd->urb;
	struct usb_iso_packet_descriptor	*desc;
	u32					t;

	/* update status for this uframe's transfers */
	desc = &urb->iso_frame_desc [itd->index];

	t = itd->hw_transaction [uframe];
	itd->hw_transaction [uframe] = 0;
	if (t & EHCI_ISOC_ACTIVE)
		desc->status = -EXDEV;
	else if (t & ISO_ERRS) {
		urb->error_count++;
		if (t & EHCI_ISOC_BUF_ERR)
			desc->status = usb_pipein (urb->pipe)
				? -ENOSR  /* couldn't read */
				: -ECOMM; /* couldn't write */
		else if (t & EHCI_ISOC_BABBLE)
			desc->status = -EOVERFLOW;
		else /* (t & EHCI_ISOC_XACTERR) */
			desc->status = -EPROTO;

		/* HC need not update length with this error */
		if (!(t & EHCI_ISOC_BABBLE))
			desc->actual_length += EHCI_ITD_LENGTH (t);
	} else {
		desc->status = 0;
		desc->actual_length += EHCI_ITD_LENGTH (t);
	}

	vdbg ("itd %p urb %p packet %d/%d trans %x status %d len %d",
		itd, urb, itd->index + 1, urb->number_of_packets,
		t, desc->status, desc->actual_length);

	/* handle completion now? */
	if ((itd->index + 1) != urb->number_of_packets)
		return flags;

	/*
	 * Always give the urb back to the driver ... expect it to submit
	 * a new urb (or resubmit this), and to have another already queued
	 * when un-interrupted transfers are needed.
	 *
	 * NOTE that for now we don't accelerate ISO unlinks; they just
	 * happen according to the current schedule.  Means a delay of
	 * up to about a second (max).
	 */
	itd_free_list (ehci, urb);
	if (urb->status == -EINPROGRESS)
		urb->status = 0;

	spin_unlock_irqrestore (&ehci->lock, flags);
	usb_hcd_giveback_urb (&ehci->hcd, urb);
	spin_lock_irqsave (&ehci->lock, flags);

	/* defer stopping schedule; completion can submit */
	ehci->periodic_urbs--;
	if (!ehci->periodic_urbs)
		disable_periodic (ehci);

	return flags;
}

/*-------------------------------------------------------------------------*/

static int itd_submit (struct ehci_hcd *ehci, struct urb *urb, int mem_flags)
{
	int		status;
	unsigned long	flags;

	dbg ("itd_submit urb %p", urb);

	/* NOTE DMA mapping assumes this ... */
	if (urb->iso_frame_desc [0].offset != 0)
		return -EINVAL;
	
	/* allocate ITDs w/o locking anything */
	status = itd_urb_transaction (ehci, urb, mem_flags);
	if (status < 0)
		return status;

	/* schedule ... need to lock */
	spin_lock_irqsave (&ehci->lock, flags);
	status = itd_schedule (ehci, urb);
	spin_unlock_irqrestore (&ehci->lock, flags);
	if (status < 0)
		itd_free_list (ehci, urb);

	return status;
}

#ifdef have_split_iso

/*-------------------------------------------------------------------------*/

/*
 * "Split ISO TDs" ... used for USB 1.1 devices going through
 * the TTs in USB 2.0 hubs.
 */

static void
sitd_free (struct ehci_hcd *ehci, struct ehci_sitd *sitd)
{
	pci_pool_free (ehci->sitd_pool, sitd, sitd->sitd_dma);
}

static struct ehci_sitd *
sitd_make (
	struct ehci_hcd	*ehci,
	struct urb	*urb,
	unsigned	index,		// urb->iso_frame_desc [index]
	unsigned	uframe,		// scheduled start
	dma_addr_t	dma,		// mapped transfer buffer
	int		mem_flags
) {
	struct ehci_sitd	*sitd;
	unsigned		length;

	sitd = pci_pool_alloc (ehci->sitd_pool, mem_flags, &dma);
	if (!sitd)
		return sitd;
	sitd->urb = urb;
	length = urb->iso_frame_desc [index].length;
	dma += urb->iso_frame_desc [index].offset;

#if 0
	// FIXME:  do the rest!
#else
	sitd_free (ehci, sitd);
	return 0;
#endif

}

static void
sitd_link (struct ehci_hcd *ehci, unsigned frame, struct ehci_sitd *sitd)
{
	u32		ptr;

	ptr = cpu_to_le32 (sitd->sitd_dma | 2);	// type 2 == sitd
	if (ehci->pshadow [frame].ptr) {
		if (!sitd->sitd_next.ptr) {
			sitd->sitd_next = ehci->pshadow [frame];
			sitd->hw_next = ehci->periodic [frame];
		} else if (sitd->sitd_next.ptr != ehci->pshadow [frame].ptr) {
			dbg ("frame %d sitd link goof", frame);
			BUG ();
		}
	}
	ehci->pshadow [frame].sitd = sitd;
	ehci->periodic [frame] = ptr;
}

static unsigned long
sitd_complete (
	struct ehci_hcd *ehci,
	struct ehci_sitd	*sitd,
	unsigned long		flags
) {
	// FIXME -- implement!

	dbg ("NYI -- sitd_complete");
	return flags;
}

/*-------------------------------------------------------------------------*/

static int sitd_submit (struct ehci_hcd *ehci, struct urb *urb, int mem_flags)
{
	// struct ehci_sitd	*first_sitd = 0;
	unsigned		frame_index;
	dma_addr_t		dma;

	dbg ("NYI -- sitd_submit");

	// FIXME -- implement!

	// FIXME:  setup one big dma mapping
	dma = 0;

	for (frame_index = 0;
			frame_index < urb->number_of_packets;
			frame_index++) {
		struct ehci_sitd	*sitd;
		unsigned		uframe;

		// FIXME:  use real arguments, schedule this!
		uframe = -1;

		sitd = sitd_make (ehci, urb, frame_index,
				uframe, dma, mem_flags);

		if (sitd) {
    /*
			if (first_sitd)
				list_add_tail (&sitd->sitd_list,
						&first_sitd->sitd_list);
			else
				first_sitd = sitd;
    */
		} else {
			// FIXME:  clean everything up
		}
	}

	// if we have a first sitd, then
		// store them all into the periodic schedule!
		// urb->hcpriv = first sitd in sitd_list

	return -ENOSYS;
}
#endif /* have_split_iso */

/*-------------------------------------------------------------------------*/

static void scan_periodic (struct ehci_hcd *ehci)
{
	unsigned	frame, clock, now_uframe, mod;
	unsigned long	flags;

	mod = ehci->periodic_size << 3;
	spin_lock_irqsave (&ehci->lock, flags);

	/*
	 * When running, scan from last scan point up to "now"
	 * else clean up by scanning everything that's left.
	 * Touches as few pages as possible:  cache-friendly.
	 * Don't scan ISO entries more than once, though.
	 */
	frame = ehci->next_uframe >> 3;
	if (HCD_IS_RUNNING (ehci->hcd.state))
		now_uframe = readl (&ehci->regs->frame_index);
	else
		now_uframe = (frame << 3) - 1;
	now_uframe %= mod;
	clock = now_uframe >> 3;

	for (;;) {
		union ehci_shadow	q, *q_p;
		u32			type, *hw_p;
		unsigned		uframes;

restart:
		/* scan schedule to _before_ current frame index */
		if (frame == clock)
			uframes = now_uframe & 0x07;
		else
			uframes = 8;

		q_p = &ehci->pshadow [frame];
		hw_p = &ehci->periodic [frame];
		q.ptr = q_p->ptr;
		type = Q_NEXT_TYPE (*hw_p);

		/* scan each element in frame's queue for completions */
		while (q.ptr != 0) {
			int			last;
			unsigned		uf;
			union ehci_shadow	temp;

			switch (type) {
			case Q_TYPE_QH:
				last = (q.qh->hw_next == EHCI_LIST_END);
				temp = q.qh->qh_next;
				type = Q_NEXT_TYPE (q.qh->hw_next);
				flags = intr_complete (ehci, frame,
						qh_get (q.qh), flags);
				qh_put (ehci, q.qh);
				q = temp;
				break;
			case Q_TYPE_FSTN:
				last = (q.fstn->hw_next == EHCI_LIST_END);
				/* for "save place" FSTNs, look at QH entries
				 * in the previous frame for completions.
				 */
				if (q.fstn->hw_prev != EHCI_LIST_END) {
					dbg ("ignoring completions from FSTNs");
				}
				type = Q_NEXT_TYPE (q.fstn->hw_next);
				q = q.fstn->fstn_next;
				break;
			case Q_TYPE_ITD:
				last = (q.itd->hw_next == EHCI_LIST_END);

				/* Unlink each (S)ITD we see, since the ISO
				 * URB model forces constant rescheduling.
				 * That complicates sharing uframes in ITDs,
				 * and means we need to skip uframes the HC
				 * hasn't yet processed.
				 */
				for (uf = 0; uf < uframes; uf++) {
					if (q.itd->hw_transaction [uf] != 0) {
						temp = q;
						*q_p = q.itd->itd_next;
						*hw_p = q.itd->hw_next;
						type = Q_NEXT_TYPE (*hw_p);

						/* might free q.itd ... */
						flags = itd_complete (ehci,
							temp.itd, uf, flags);
						break;
					}
				}
				/* we might skip this ITD's uframe ... */
				if (uf == uframes) {
					q_p = &q.itd->itd_next;
					hw_p = &q.itd->hw_next;
					type = Q_NEXT_TYPE (q.itd->hw_next);
				}

				q = *q_p;
				break;
#ifdef have_split_iso
			case Q_TYPE_SITD:
				last = (q.sitd->hw_next == EHCI_LIST_END);
				flags = sitd_complete (ehci, q.sitd, flags);
				type = Q_NEXT_TYPE (q.sitd->hw_next);

				// FIXME unlink SITD after split completes
				q = q.sitd->sitd_next;
				break;
#endif /* have_split_iso */
			default:
				dbg ("corrupt type %d frame %d shadow %p",
					type, frame, q.ptr);
				// BUG ();
				last = 1;
				q.ptr = 0;
			}

			/* did completion remove an interior q entry? */
			if (unlikely (q.ptr == 0 && !last))
				goto restart;
		}

		/* stop when we catch up to the HC */

		// FIXME:  this assumes we won't get lapped when
		// latencies climb; that should be rare, but...
		// detect it, and just go all the way around.
		// FLR might help detect this case, so long as latencies
		// don't exceed periodic_size msec (default 1.024 sec).

		// FIXME:  likewise assumes HC doesn't halt mid-scan

		if (frame == clock) {
			unsigned	now;

			if (!HCD_IS_RUNNING (ehci->hcd.state))
				break;
			ehci->next_uframe = now_uframe;
			now = readl (&ehci->regs->frame_index) % mod;
			if (now_uframe == now)
				break;

			/* rescan the rest of this frame, then ... */
			now_uframe = now;
			clock = now_uframe >> 3;
		} else
			frame = (frame + 1) % ehci->periodic_size;
	} 
	spin_unlock_irqrestore (&ehci->lock, flags);
}