6 files changed, 140 insertions, 14 deletions

diff --git a/Documentation/ABI/testing/sysfs-module b/Documentation/ABI/testing/sysfs-module
index cfcec3bffc0a..9489ea8e294c 100644
--- a/Documentation/ABI/testing/sysfs-module
+++ b/Documentation/ABI/testing/sysfs-module
@@ -10,3 +10,26 @@ KernelVersion:	2.6.35
 Contact:        masa-korg@dsn.okisemi.com
 Description:    Write/read Option ROM data.
 
+
+What:           /sys/module/ehci_hcd/drivers/.../uframe_periodic_max
+Date:           July 2011
+KernelVersion:  3.1
+Contact:        Kirill Smelkov <kirr@mns.spb.ru>
+Description:    Maximum time allowed for periodic transfers per microframe (μs)
+
+                [ USB 2.0 sets maximum allowed time for periodic transfers per
+                  microframe to be 80%, that is 100 microseconds out of 125
+                  microseconds (full microframe).
+
+                  However there are cases, when 80% max isochronous bandwidth is
+                  too limiting. For example two video streams could require 110
+                  microseconds of isochronous bandwidth per microframe to work
+                  together. ]
+
+                Through this setting it is possible to raise the limit so that
+                the host controller would allow allocating more than 100
+                microseconds of periodic bandwidth per microframe.
+
+                Beware, non-standard modes are usually not thoroughly tested by
+                hardware designers, and the hardware can malfunction when this
+                setting differ from default 100.
diff --git a/Documentation/usb/ehci.txt b/Documentation/usb/ehci.txt
index 9dcafa7d930d..160bd6c3ab7b 100644
--- a/Documentation/usb/ehci.txt
+++ b/Documentation/usb/ehci.txt
@@ -210,3 +210,5 @@ TBD:  Interrupt and ISO transfer performance issues.  Those periodic
 transfers are fully scheduled, so the main issue is likely to be how
 to trigger "high bandwidth" modes.
 
+TBD:  More than standard 80% periodic bandwidth allocation is possible
+through sysfs uframe_periodic_max parameter. Describe that.
diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 8306155de9e5..4ee62bef3723 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -572,6 +572,12 @@ static int ehci_init(struct usb_hcd *hcd)
         hcc_params = ehci_readl(ehci, &ehci->caps->hcc_params);
 
         /*
+         * by default set standard 80% (== 100 usec/uframe) max periodic
+         * bandwidth as required by USB 2.0
+         */
+        ehci->uframe_periodic_max = 100;
+
+        /*
          * hw default: 1K periodic list heads, one per frame.
          * periodic_size can shrink by USBCMD update if hcc_params allows.
          */
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 6c9fbe352f73..2abf8543f083 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -172,7 +172,7 @@ periodic_usecs (struct ehci_hcd *ehci, unsigned frame, unsigned uframe)
                 }
         }
 #ifdef  DEBUG
-        if (usecs > 100)
+        if (usecs > ehci->uframe_periodic_max)
                 ehci_err (ehci, "uframe %d sched overrun: %d usecs\n",
                         frame * 8 + uframe, usecs);
 #endif
@@ -709,11 +709,8 @@ static int check_period (
         if (uframe >= 8)
                 return 0;
 
-        /*
-         * 80% periodic == 100 usec/uframe available
-         * convert "usecs we need" to "max already claimed"
-         */
-        usecs = 100 - usecs;
+        /* convert "usecs we need" to "max already claimed" */
+        usecs = ehci->uframe_periodic_max - usecs;
 
         /* we "know" 2 and 4 uframe intervals were rejected; so
          * for period 0, check _every_ microframe in the schedule.
@@ -1286,9 +1283,9 @@ itd_slot_ok (
 {
         uframe %= period;
         do {
-                /* can't commit more than 80% periodic == 100 usec */
+                /* can't commit more than uframe_periodic_max usec */
                 if (periodic_usecs (ehci, uframe >> 3, uframe & 0x7)
-                                > (100 - usecs))
+                                > (ehci->uframe_periodic_max - usecs))
                         return 0;
 
                 /* we know urb->interval is 2^N uframes */
@@ -1345,7 +1342,7 @@ sitd_slot_ok (
 #endif
 
                 /* check starts (OUT uses more than one) */
-                max_used = 100 - stream->usecs;
+                max_used = ehci->uframe_periodic_max - stream->usecs;
                 for (tmp = stream->raw_mask & 0xff; tmp; tmp >>= 1, uf++) {
                         if (periodic_usecs (ehci, frame, uf) > max_used)
                                 return 0;
@@ -1354,7 +1351,7 @@ sitd_slot_ok (
                 /* for IN, check CSPLIT */
                 if (stream->c_usecs) {
                         uf = uframe & 7;
-                        max_used = 100 - stream->c_usecs;
+                        max_used = ehci->uframe_periodic_max - stream->c_usecs;
                         do {
                                 tmp = 1 << uf;
                                 tmp <<= 8;
diff --git a/drivers/usb/host/ehci-sysfs.c b/drivers/usb/host/ehci-sysfs.c
index 29824a98aec9..14ced00ba220 100644
--- a/drivers/usb/host/ehci-sysfs.c
+++ b/drivers/usb/host/ehci-sysfs.c
@@ -74,21 +74,117 @@ static ssize_t store_companion(struct device *dev,
 }
 static DEVICE_ATTR(companion, 0644, show_companion, store_companion);
 
+
+/*
+ * Display / Set uframe_periodic_max
+ */
+static ssize_t show_uframe_periodic_max(struct device *dev,
+                                        struct device_attribute *attr,
+                                        char *buf)
+{
+        struct ehci_hcd         *ehci;
+        int                     n;
+
+        ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
+        n = scnprintf(buf, PAGE_SIZE, "%d\n", ehci->uframe_periodic_max);
+        return n;
+}
+
+
+static ssize_t store_uframe_periodic_max(struct device *dev,
+                                        struct device_attribute *attr,
+                                        const char *buf, size_t count)
+{
+        struct ehci_hcd         *ehci;
+        unsigned                uframe_periodic_max;
+        unsigned                frame, uframe;
+        unsigned short          allocated_max;
+        unsigned long           flags;
+        ssize_t                 ret;
+
+        ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
+        if (kstrtouint(buf, 0, &uframe_periodic_max) < 0)
+                return -EINVAL;
+
+        if (uframe_periodic_max < 100 || uframe_periodic_max >= 125) {
+                ehci_info(ehci, "rejecting invalid request for "
+                                "uframe_periodic_max=%u\n", uframe_periodic_max);
+                return -EINVAL;
+        }
+
+        ret = -EINVAL;
+
+        /*
+         * lock, so that our checking does not race with possible periodic
+         * bandwidth allocation through submitting new urbs.
+         */
+        spin_lock_irqsave (&ehci->lock, flags);
+
+        /*
+         * for request to decrease max periodic bandwidth, we have to check
+         * every microframe in the schedule to see whether the decrease is
+         * possible.
+         */
+        if (uframe_periodic_max < ehci->uframe_periodic_max) {
+                allocated_max = 0;
+
+                for (frame = 0; frame < ehci->periodic_size; ++frame)
+                        for (uframe = 0; uframe < 7; ++uframe)
+                                allocated_max = max(allocated_max,
+                                                    periodic_usecs (ehci, frame, uframe));
+
+                if (allocated_max > uframe_periodic_max) {
+                        ehci_info(ehci,
+                                "cannot decrease uframe_periodic_max becase "
+                                "periodic bandwidth is already allocated "
+                                "(%u > %u)\n",
+                                allocated_max, uframe_periodic_max);
+                        goto out_unlock;
+                }
+        }
+
+        /* increasing is always ok */
+
+        ehci_info(ehci, "setting max periodic bandwidth to %u%% "
+                        "(== %u usec/uframe)\n",
+                        100*uframe_periodic_max/125, uframe_periodic_max);
+
+        if (uframe_periodic_max != 100)
+                ehci_warn(ehci, "max periodic bandwidth set is non-standard\n");
+
+        ehci->uframe_periodic_max = uframe_periodic_max;
+        ret = count;
+
+out_unlock:
+        spin_unlock_irqrestore (&ehci->lock, flags);
+        return ret;
+}
+static DEVICE_ATTR(uframe_periodic_max, 0644, show_uframe_periodic_max, store_uframe_periodic_max);
+
+
 static inline int create_sysfs_files(struct ehci_hcd *ehci)
 {
+        struct device   *controller = ehci_to_hcd(ehci)->self.controller;
         int     i = 0;
 
         /* with integrated TT there is no companion! */
         if (!ehci_is_TDI(ehci))
-                i = device_create_file(ehci_to_hcd(ehci)->self.controller,
-                                       &dev_attr_companion);
+                i = device_create_file(controller, &dev_attr_companion);
+        if (i)
+                goto out;
+
+        i = device_create_file(controller, &dev_attr_uframe_periodic_max);
+out:
         return i;
 }
 
 static inline void remove_sysfs_files(struct ehci_hcd *ehci)
 {
+        struct device   *controller = ehci_to_hcd(ehci)->self.controller;
+
         /* with integrated TT there is no companion! */
         if (!ehci_is_TDI(ehci))
-                device_remove_file(ehci_to_hcd(ehci)->self.controller,
-                                   &dev_attr_companion);
+                device_remove_file(controller, &dev_attr_companion);
+
+        device_remove_file(controller, &dev_attr_uframe_periodic_max);
 }
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index bd6ff489baf9..fa3129fe1ee0 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -87,6 +87,8 @@ struct ehci_hcd {			/* one per controller */
         union ehci_shadow       *pshadow;       /* mirror hw periodic table */
         int                     next_uframe;    /* scan periodic, start here */
         unsigned                periodic_sched; /* periodic activity count */
+        unsigned                uframe_periodic_max; /* max periodic time per uframe */
+
 
         /* list of itds & sitds completed while clock_frame was still active */
         struct list_head        cached_itd_list;