2 files changed, 234 insertions, 2 deletions

diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
index e27b79a3c05f..c060eb9b3b19 100644
--- a/drivers/usb/host/Kconfig
+++ b/drivers/usb/host/Kconfig
@@ -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"
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 5871944e6145..4859900bd135 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -163,6 +163,190 @@ static int same_tt (struct usb_device *dev1, struct usb_device *dev2)
                 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;