This is Dan Streetman's patch to improve TT scheduling; it's EHCI-specific
for now (though other high speed host controllers will need some of the
same logic). I merged Dan's three patches into one. It works for me in
light usage.
Dan, many thanks for this work!
- Dave
From [EMAIL PROTECTED] Tue Dec 20 11:29:39 2005
This updates the EHCI driver by adding an improved scheduler for the
transaction translators, found in USB 2.0 hubs and used for low and
full speed devices.
- adds periodic_tt_usecs() and some helper functions, which does
the same thing that "periodic_usecs" does, except on the other
side of the TT, i.e. it calculates the low/fullspeed bandwidth
usage instead of highspeed.
- adds a tt_available() function which is the new implementation
of what tt_no_collision() does ... while tt_no_collision() ensures
that each TT handles only 1 periodic transfer at a time (a very
pessimistic approach) this version instead tracks bandwidth and
allows each TT to handle as many transfers as will fit on each TT's
downstream bus (closer to best-case).
The new scheduler is selected by a config option, marked as EXPERIMENTAL
so it can be tested (and more broadly reviewed) for a while until it
seems safe to remove the original scheduler.
Signed-off-by: Dan Streetman <[EMAIL PROTECTED]>
Signed-off-by: David Brownell <[EMAIL PROTECTED]>
Index: g26/drivers/usb/host/Kconfig
===================================================================
--- g26.orig/drivers/usb/host/Kconfig 2006-05-24 09:14:11.000000000 -0700
+++ g26/drivers/usb/host/Kconfig 2006-05-24 09:19:43.000000000 -0700
@@ -47,7 +47,25 @@ config USB_EHCI_ROOT_HUB_TT
controller is needed. It's safe to say "y" even if your
controller doesn't support this feature.
- This supports the EHCI implementation from TransDimension Inc.
+ This supports the EHCI implementation that's originally
+ from ARC, and has since changed hands a few times.
+
+config USB_EHCI_TT_NEWSCHED
+ bool "Improved Transaction Translator scheduling (EXPERIMENTAL)"
+ depends on USB_EHCI_HCD && EXPERIMENTAL
+ ---help---
+ This changes the periodic scheduling code to fill more of the low
+ and full speed bandwidth available from the Transaction Translator
+ (TT) in USB 2.0 hubs. Without this, only one transfer will be
+ issued in each microframe, significantly reducing the number of
+ periodic low/fullspeed transfers possible.
+
+ If you have multiple periodic low/fullspeed devices connected to a
+ highspeed USB hub which is connected to a highspeed USB Host
+ Controller, and some of those devices will not work correctly
+ (possibly due to "ENOSPC" or "-28" errors), say Y.
+
+ If unsure, say N.
config USB_ISP116X_HCD
tristate "ISP116X HCD support"
Index: g26/drivers/usb/host/ehci-sched.c
===================================================================
--- g26.orig/drivers/usb/host/ehci-sched.c 2006-05-24 09:14:11.000000000 -0700
+++ g26/drivers/usb/host/ehci-sched.c 2006-05-24 09:31:43.000000000 -0700
@@ -163,6 +163,190 @@ static int same_tt (struct usb_device *d
return 1;
}
+#ifdef CONFIG_USB_EHCI_TT_NEWSCHED
+
+/* Which uframe does the low/fullspeed transfer start in?
+ *
+ * The parameter is the mask of ssplits in "H-frame" terms
+ * and this returns the transfer start uframe in "B-frame" terms,
+ * which allows both to match, e.g. a ssplit in "H-frame" uframe 0
+ * will cause a transfer in "B-frame" uframe 0. "B-frames" lag
+ * "H-frames" by 1 uframe. See the EHCI spec sec 4.5 and figure 4.7.
+ */
+static inline unsigned char tt_start_uframe(struct ehci_hcd *ehci, __le32 mask)
+{
+ unsigned char smask = QH_SMASK & le32_to_cpu(mask);
+ if (!smask) {
+ ehci_err(ehci, "invalid empty smask!\n");
+ /* uframe 7 can't have bw so this will indicate failure */
+ return 7;
+ }
+ return ffs(smask) - 1;
+}
+
+static const unsigned char
+max_tt_usecs[] = { 125, 125, 125, 125, 125, 125, 30, 0 };
+
+/* carryover low/fullspeed bandwidth that crosses uframe boundries */
+static inline void carryover_tt_bandwidth(unsigned short tt_usecs[8])
+{
+ int i;
+ for (i=0; i<7; i++) {
+ if (max_tt_usecs[i] < tt_usecs[i]) {
+ tt_usecs[i+1] += tt_usecs[i] - max_tt_usecs[i];
+ tt_usecs[i] = max_tt_usecs[i];
+ }
+ }
+}
+
+/* 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 seperate 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]
+)
+{
+ __le32 *hw_p = &ehci->periodic [frame];
+ union ehci_shadow *q = &ehci->pshadow [frame];
+ unsigned char uf;
+
+ memset(tt_usecs, 0, 16);
+
+ while (q->ptr) {
+ switch (Q_NEXT_TYPE(*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->dev)) {
+ uf = tt_start_uframe(ehci, q->qh->hw_info2);
+ tt_usecs[uf] += q->qh->tt_usecs;
+ }
+ hw_p = &q->qh->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->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
+ * specified frame/uframe. Note that (as summarized in section 11.19
+ * of the usb 2.0 spec) TTs can buffer multiple transactions for each
+ * uframe.
+ *
+ * The uframe parameter is when the fullspeed/lowspeed transfer
+ * should be executed in "B-frame" terms, which is the same as the
+ * highspeed ssplit's uframe (which is in "H-frame" terms). For example
+ * a ssplit in "H-frame" 0 causes a transfer in "B-frame" 0.
+ * See the EHCI spec sec 4.5 and fig 4.7.
+ *
+ * This checks if the full/lowspeed bus, at the specified starting uframe,
+ * has the specified bandwidth available, according to rules listed
+ * in USB 2.0 spec section 11.18.1 fig 11-60.
+ *
+ * This does not check if the transfer would exceed the max ssplit
+ * limit of 16, specified in USB 2.0 spec section 11.18.4 requirement #4,
+ * since proper scheduling limits ssplits to less than 16 per uframe.
+ */
+static int tt_available (
+ struct ehci_hcd *ehci,
+ unsigned period,
+ struct usb_device *dev,
+ unsigned frame,
+ unsigned uframe,
+ u16 usecs
+)
+{
+ if ((period == 0) || (uframe >= 7)) /* error */
+ return 0;
+
+ for (; frame < ehci->periodic_size; frame += period) {
+ unsigned short tt_usecs[8];
+
+ periodic_tt_usecs (ehci, dev, frame, tt_usecs);
+
+ ehci_vdbg(ehci, "tt frame %d check %d usecs start uframe %d in"
+ " schedule %d/%d/%d/%d/%d/%d/%d/%d\n",
+ frame, usecs, uframe,
+ tt_usecs[0], tt_usecs[1], tt_usecs[2], tt_usecs[3],
+ tt_usecs[4], tt_usecs[5], tt_usecs[6], tt_usecs[7]);
+
+ if (max_tt_usecs[uframe] <= tt_usecs[uframe]) {
+ ehci_vdbg(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 < usecs) {
+ int ufs = (usecs / 125) - 1;
+ int i;
+ for (i = uframe; i < (uframe + ufs) && i < 8; i++)
+ if (0 < tt_usecs[i]) {
+ ehci_vdbg(ehci,
+ "multi-uframe xfer can't fit "
+ "in frame %d uframe %d\n",
+ frame, i);
+ return 0;
+ }
+ }
+
+ tt_usecs[uframe] += usecs;
+
+ carryover_tt_bandwidth(tt_usecs);
+
+ /* fail if the carryover pushed bw past the last uframe's limit */
+ if (max_tt_usecs[7] < tt_usecs[7]) {
+ ehci_vdbg(ehci,
+ "tt unavailable usecs %d frame %d uframe %d\n",
+ usecs, frame, uframe);
+ return 0;
+ }
+ }
+
+ return 1;
+}
+
+#else
+
/* 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.
@@ -237,6 +421,8 @@ static int tt_no_collision (
return 1;
}
+#endif /* CONFIG_USB_EHCI_TT_NEWSCHED */
+
/*-------------------------------------------------------------------------*/
static int enable_periodic (struct ehci_hcd *ehci)
@@ -481,7 +667,7 @@ static int check_intr_schedule (
)
{
int retval = -ENOSPC;
- u8 mask;
+ u8 mask = 0;
if (qh->c_usecs && uframe >= 6) /* FSTN territory? */
goto done;
@@ -494,6 +680,24 @@ static int check_intr_schedule (
goto done;
}
+#ifdef CONFIG_USB_EHCI_TT_NEWSCHED
+ if (tt_available (ehci, qh->period, qh->dev, frame, uframe,
+ qh->tt_usecs)) {
+ unsigned i;
+
+ /* TODO : this may need FSTN for SSPLIT in uframe 5. */
+ for (i=uframe+1; i<8 && i<uframe+4; i++)
+ if (!check_period (ehci, frame, i,
+ qh->period, qh->c_usecs))
+ goto done;
+ else
+ mask |= 1 << i;
+
+ retval = 0;
+
+ *c_maskp = cpu_to_le32 (mask << 8);
+ }
+#else
/* Make sure this tt's buffer is also available for CSPLITs.
* We pessimize a bit; probably the typical full speed case
* doesn't need the second CSPLIT.
@@ -514,6 +718,7 @@ static int check_intr_schedule (
goto done;
retval = 0;
}
+#endif
done:
return retval;
}
@@ -1047,12 +1252,21 @@ sitd_slot_ok (
frame = uframe >> 3;
uf = uframe & 7;
+#ifdef CONFIG_USB_EHCI_TT_NEWSCHED
+ /* The tt's fullspeed bus bandwidth must be available.
+ * tt_available scheduling guarantees 10+% for control/bulk.
+ */
+ if (!tt_available (ehci, period_uframes << 3,
+ stream->udev, frame, uf, stream->tt_usecs))
+ return 0;
+#else
/* tt must be idle for start(s), any gap, and csplit.
* assume scheduling slop leaves 10+% for control/bulk.
*/
if (!tt_no_collision (ehci, period_uframes << 3,
stream->udev, frame, mask))
return 0;
+#endif
/* check starts (OUT uses more than one) */
max_used = 100 - stream->usecs;
