Ok here's the biggest patch... :)
This adds a function "tt_available" and helper functions that determine if
a particular transaction translator is "available" for a periodic
transfer. This is similar to the existing "tt_no_collision" but that
function simply uses the ssplit/csplit masks to prevent multiple
ssplits/csplits during the same uframe, while this new function does
downstream bus scheduling, i.e. using the tt_usecs from each ehci_qh or
ehci_iso_stream to schedule transfers when the downstream low/full speed
bus is available. This adheres to the USB 2.0 spec section 11.18.1
(figure 11-60) and section 11.18.4 requirement #4. This does allow
multiple ssplits/csplits during a single uframe, up to 16 as specified by
the USB 2.0 spec.
Note this only adds the function, later patches change the driver to use
it and remove the tt_no_collision function.
Signed-off-by: Dan Streetman <[EMAIL PROTECTED]>
diff -urpN a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
--- a/drivers/usb/host/ehci-sched.c 2005-08-03 12:25:25.000000000 -0400
+++ b/drivers/usb/host/ehci-sched.c 2005-08-03 12:43:41.000000000 -0400
@@ -163,6 +163,196 @@ static int same_tt (struct usb_device *d
return 1;
}
+static const unsigned char
+MAX_TT_USECS[] = { 125, 125, 125, 125, 125, 125, 30, 0 };
+
+/* FIXME - can have ssplits in uframe 7 with FSTN */
+static const unsigned char
+MAX_TT_SSPLIT[] = { 16, 16, 16, 16, 16, 16, 0, 0 };
+
+struct tt_frame_bw {
+ short usecs[8]; /* used usecs per uframe */
+ char ssplits[8]; /* number of ssplits per uframe */
+};
+
+static void
+update_tt_frame_bw (struct tt_frame_bw *bw, unsigned uf, int tt_usecs)
+{
+ if (!uf) {
+ dbg ("%s : no ssplit, is this FSTN?\n", __FUNCTION__);
+ return;
+ }
+
+ do {
+ bw->usecs[uf] += tt_usecs;
+ tt_usecs = bw->usecs[uf] - MAX_TT_USECS[uf];
+ if (0 < tt_usecs)
+ bw->usecs[uf] = MAX_TT_USECS[uf];
+ } while ((0 < tt_usecs) && (++uf < 7));
+}
+
+/* how many of the tt's periodic downstream 1000 usecs are allocated? */
+static void
+calc_periodic_tt_usecs (
+ struct ehci_hcd *ehci,
+ struct usb_device *dev,
+ unsigned frame,
+ struct tt_frame_bw *bw
+)
+{
+ union ehci_shadow here;
+ __le32 type;
+
+ memset(bw, 0, sizeof(*bw));
+
+ 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)) {
+ unsigned uf = ffs (0x3f &
+ le32_to_cpu (here.qh->hw_info2));
+
+ /* the ssplit is 1 uframe before the
+ * tt downstream transfer
+ */
+ if (uf)
+ bw->ssplits[uf-1]++;
+
+ update_tt_frame_bw (bw, uf,
+ here.qh->tt_usecs);
+ }
+ type = Q_NEXT_TYPE (here.qh->hw_next);
+ here = here.qh->qh_next;
+ continue;
+ case Q_TYPE_SITD:
+ if (same_tt (dev, here.sitd->urb->dev)) {
+ int i;
+ long smask = le32_to_cpu (here.sitd->hw_uframe);
+ unsigned uf = ffs (0x3f & smask);
+
+ /* isoc out can have multiple ssplits,
+ * each ssplit 1 uframe before its
+ * tt downstream transfer
+ */
+ for (i=0; i<8; i++)
+ if (test_bit(i, &smask))
+ bw->ssplits[i]++;
+
+ update_tt_frame_bw (bw, uf,
+ here.sitd->stream->tt_usecs);
+ }
+ type = Q_NEXT_TYPE (here.sitd->hw_next);
+ here = here.sitd->sitd_next;
+ continue;
+ // case Q_TYPE_FSTN:
+ default:
+ ehci_dbg (ehci,
+ "ignoring periodic frame %d bogus type %d\n",
+ frame, type);
+ }
+ }
+}
+
+/* return true if the device's tt's downstream bus is available
+ * for a periodic transfer starting at the specified frame/uframe.
+ * Note that the uframe parameter is when the downstream transfer
+ * should be executed, which is 1 uframe after the ssplit.
+ * This checks 2 things:
+ * 1) if the bus, at the specified starting uframe,
+ * has the specified bandwidth (max 125 us).
+ * note no periodic xfers allowed in uframe 7,
+ * and the max bw in uframe 6 is only (approx calc) ~30 us.
+ * (USB 2.0 spec section 11.18.1 fig 11-60)
+ * 2) if the transfer would exceed the max ssplit limit of 16
+ * (USB 2.0 spec section 11.18.4 requirement #4).
+ */
+static int tt_available (
+ struct ehci_hcd *ehci,
+ unsigned period,
+ struct usb_device *dev,
+ unsigned frame,
+ unsigned uframe,
+ u16 tt_usecs
+)
+{
+ if ((period == 0) || (uframe >= 7)) /* error */
+ return 0;
+
+ /* not yet supported : FSTN (ssplit in uframe 7) */
+ if (uframe == 0)
+ return 0;
+
+ for (; frame < ehci->periodic_size; frame += period) {
+ struct tt_frame_bw bw;
+ int i;
+
+ calc_periodic_tt_usecs (ehci, dev, frame, &bw);
+
+ ehci_vdbg (ehci, "tt frame %d check %d usecs start uframe %d in"
+ " schedule %d/%d/%d/%d/%d/%d/%d/%d\n",
+ frame, tt_usecs, uframe,
+ bw.usecs[0], bw.usecs[1], bw.usecs[2], bw.usecs[3],
+ bw.usecs[4], bw.usecs[5], bw.usecs[6], bw.usecs[7]);
+
+ /* reject if desired uframe is already 100% scheduled */
+ if (MAX_TT_USECS[uframe] <= bw.usecs[uframe]) {
+ ehci_dbg (ehci, "frame %d uframe %d fully scheduled\n",
+ frame, uframe);
+ return 0;
+ }
+
+ /* special case for isoc transfers larger than 125us:
+ * the first and each subsequent fully used uframe
+ * must be empty, so as to not illegally delay
+ * already scheduled transactions
+ */
+ if (125 < tt_usecs) {
+ int ufs = tt_usecs / 125;
+ for (i = uframe; i < (uframe + ufs) && i < 8; i++)
+ if (0 < bw.usecs[i]) {
+ ehci_dbg(ehci, "Isoc transfer would "
+ "delay existing transfer in "
+ "frame %d uframe %d\n",
+ frame, uframe);
+ return 0;
+ }
+ }
+
+ update_tt_frame_bw (&bw, uframe, tt_usecs);
+
+ /* overscheduled if any bw has rolled over into uframe 7 */
+ if (bw.usecs[7]) {
+ ehci_dbg (ehci,
+ "tt does not have %d usecs available "
+ "in frame %d uframe %d\n",
+ tt_usecs, frame, uframe);
+ return 0;
+ }
+
+ /* no uframe can have more than MAX_TT_SSPLIT ssplits */
+ for (i = 0; i < 8; i++)
+ if (MAX_TT_SSPLIT[i] < bw.ssplits[i]) {
+ ehci_dbg (ehci,
+ "tt max ssplit in frame %d uframe %d\n",
+ frame, uframe);
+ return 0;
+ }
+ }
+
+ /* tt's downstream bus has available bw */
+ ehci_dbg (ehci,
+ "tt available for %d usec transfer starting "
+ "in frame %d uframe %d every %d frames\n",
+ tt_usecs, frame % period, uframe, period);
+ 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.
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