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USB: EHCI: Allow users to override 80% max periodic bandwidth
There are cases, when 80% max isochronous bandwidth is too limiting.
For example I have two USB video capture cards which stream uncompressed
video, and to stream full NTSC + PAL videos we'd need
NTSC 640x480 YUV422 @30fps ~17.6 MB/s
PAL 720x576 YUV422 @25fps ~19.7 MB/s
isoc bandwidth.
Now, due to limited alt settings in capture devices NTSC one ends up
streaming with max_pkt_size=2688 and PAL with max_pkt_size=2892, both
with interval=1. In terms of microframe time allocation this gives
NTSC ~53us
PAL ~57us
and together
~110us > 100us == 80% of 125us uframe time.
So those two devices can't work together simultaneously because the'd
over allocate isochronous bandwidth.
80% seemed a bit arbitrary to me, and I've tried to raise it to 90% and
both devices started to work together, so I though sometimes it would be
a good idea for users to override hardcoded default of max 80% isoc
bandwidth.
After all, isn't it a user who should decide how to load the bus? If I
can live with 10% or even 5% bulk bandwidth that should be ok. I'm a USB
newcomer, but that 80% set in stone by USB 2.0 specification seems to be
chosen pretty arbitrary to me, just to serve as a reasonable default.
NOTE 1
~~~~~~
for two streams with max_pkt_size=3072 (worst case) both time
allocation would be 60us+60us=120us which is 96% periodic bandwidth
leaving 4% for bulk and control. Alan Stern suggested that bulk then
would be problematic (less than 300*8 bittimes left per microframe), but
I think that is still enough for control traffic.
NOTE 2
~~~~~~
Sarah Sharp expressed concern that maxing out periodic bandwidth
could lead to vendor-specific hardware bugs on host controllers, because
> It's entirely possible that you'll run into
> vendor-specific bugs if you try to pack the schedule with isochronous
> transfers. I don't think any hardware designer would seriously test or
> validate their hardware with a schedule that is basically a violation of
> the USB bus spec (more than 80% for periodic transfers).
So far I've only tested this patch on my HP Mini 5103 with N10 chipset
kirr@mini:~$ lspci
00:00.0 Host bridge: Intel Corporation N10 Family DMI Bridge
00:02.0 VGA compatible controller: Intel Corporation N10 Family Integrated Graphics Controller
00:02.1 Display controller: Intel Corporation N10 Family Integrated Graphics Controller
00:1b.0 Audio device: Intel Corporation N10/ICH 7 Family High Definition Audio Controller (rev 02)
00:1c.0 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 1 (rev 02)
00:1c.3 PCI bridge: Intel Corporation N10/ICH 7 Family PCI Express Port 4 (rev 02)
00:1d.0 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #1 (rev 02)
00:1d.1 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #2 (rev 02)
00:1d.2 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #3 (rev 02)
00:1d.3 USB Controller: Intel Corporation N10/ICH 7 Family USB UHCI Controller #4 (rev 02)
00:1d.7 USB Controller: Intel Corporation N10/ICH 7 Family USB2 EHCI Controller (rev 02)
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev e2)
00:1f.0 ISA bridge: Intel Corporation NM10 Family LPC Controller (rev 02)
00:1f.2 SATA controller: Intel Corporation N10/ICH7 Family SATA AHCI Controller (rev 02)
01:00.0 Network controller: Broadcom Corporation BCM4313 802.11b/g/n Wireless LAN Controller (rev 01)
02:00.0 Ethernet controller: Marvell Technology Group Ltd. 88E8059 PCI-E Gigabit Ethernet Controller (rev 11)
and the system works stable with 110us/uframe (~88%) isoc bandwith allocated for
above-mentioned isochronous transfers.
NOTE 3
~~~~~~
This feature is off by default. I mean max periodic bandwidth is set to
100us/uframe by default exactly as it was before the patch. So only those of us
who need the extreme settings are taking the risk - normal users who do not
alter uframe_periodic_max sysfs attribute should not see any change at all.
NOTE 4
~~~~~~
I've tried to update documentation in Documentation/ABI/ thoroughly, but
only "TBD" was put into Documentation/usb/ehci.txt -- the text there seems
to be outdated and much needing refreshing, before it could be amended.
Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Kirill Smelkov
Greg Kroah-Hartman
parent
4c67045bfc
commit
cc62a7eb63
@ -10,3 +10,26 @@ KernelVersion: 2.6.35
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Contact: masa-korg@dsn.okisemi.com
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Description: Write/read Option ROM data.
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What: /sys/module/ehci_hcd/drivers/.../uframe_periodic_max
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Date: July 2011
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KernelVersion: 3.1
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Contact: Kirill Smelkov <kirr@mns.spb.ru>
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Description: Maximum time allowed for periodic transfers per microframe (μs)
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[ USB 2.0 sets maximum allowed time for periodic transfers per
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microframe to be 80%, that is 100 microseconds out of 125
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microseconds (full microframe).
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However there are cases, when 80% max isochronous bandwidth is
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too limiting. For example two video streams could require 110
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microseconds of isochronous bandwidth per microframe to work
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together. ]
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Through this setting it is possible to raise the limit so that
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the host controller would allow allocating more than 100
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microseconds of periodic bandwidth per microframe.
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Beware, non-standard modes are usually not thoroughly tested by
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hardware designers, and the hardware can malfunction when this
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setting differ from default 100.
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@ -210,3 +210,5 @@ TBD: Interrupt and ISO transfer performance issues. Those periodic
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transfers are fully scheduled, so the main issue is likely to be how
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to trigger "high bandwidth" modes.
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TBD: More than standard 80% periodic bandwidth allocation is possible
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through sysfs uframe_periodic_max parameter. Describe that.
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@ -571,6 +571,12 @@ static int ehci_init(struct usb_hcd *hcd)
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hcc_params = ehci_readl(ehci, &ehci->caps->hcc_params);
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/*
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* by default set standard 80% (== 100 usec/uframe) max periodic
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* bandwidth as required by USB 2.0
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*/
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ehci->uframe_periodic_max = 100;
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/*
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* hw default: 1K periodic list heads, one per frame.
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* periodic_size can shrink by USBCMD update if hcc_params allows.
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@ -172,7 +172,7 @@ periodic_usecs (struct ehci_hcd *ehci, unsigned frame, unsigned uframe)
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}
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}
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#ifdef DEBUG
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if (usecs > 100)
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if (usecs > ehci->uframe_periodic_max)
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ehci_err (ehci, "uframe %d sched overrun: %d usecs\n",
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frame * 8 + uframe, usecs);
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#endif
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@ -709,11 +709,8 @@ static int check_period (
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if (uframe >= 8)
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return 0;
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/*
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* 80% periodic == 100 usec/uframe available
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* convert "usecs we need" to "max already claimed"
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*/
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usecs = 100 - usecs;
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/* convert "usecs we need" to "max already claimed" */
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usecs = ehci->uframe_periodic_max - usecs;
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/* we "know" 2 and 4 uframe intervals were rejected; so
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* for period 0, check _every_ microframe in the schedule.
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@ -1286,9 +1283,9 @@ itd_slot_ok (
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{
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uframe %= period;
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do {
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/* can't commit more than 80% periodic == 100 usec */
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/* can't commit more than uframe_periodic_max usec */
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if (periodic_usecs (ehci, uframe >> 3, uframe & 0x7)
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> (100 - usecs))
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> (ehci->uframe_periodic_max - usecs))
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return 0;
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/* we know urb->interval is 2^N uframes */
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@ -1345,7 +1342,7 @@ sitd_slot_ok (
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#endif
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/* check starts (OUT uses more than one) */
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max_used = 100 - stream->usecs;
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max_used = ehci->uframe_periodic_max - stream->usecs;
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for (tmp = stream->raw_mask & 0xff; tmp; tmp >>= 1, uf++) {
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if (periodic_usecs (ehci, frame, uf) > max_used)
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return 0;
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@ -1354,7 +1351,7 @@ sitd_slot_ok (
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/* for IN, check CSPLIT */
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if (stream->c_usecs) {
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uf = uframe & 7;
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max_used = 100 - stream->c_usecs;
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max_used = ehci->uframe_periodic_max - stream->c_usecs;
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do {
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tmp = 1 << uf;
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tmp <<= 8;
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@ -74,21 +74,117 @@ static ssize_t store_companion(struct device *dev,
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}
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static DEVICE_ATTR(companion, 0644, show_companion, store_companion);
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/*
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* Display / Set uframe_periodic_max
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*/
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static ssize_t show_uframe_periodic_max(struct device *dev,
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struct device_attribute *attr,
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char *buf)
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{
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struct ehci_hcd *ehci;
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int n;
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ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
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n = scnprintf(buf, PAGE_SIZE, "%d\n", ehci->uframe_periodic_max);
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return n;
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}
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static ssize_t store_uframe_periodic_max(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct ehci_hcd *ehci;
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unsigned uframe_periodic_max;
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unsigned frame, uframe;
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unsigned short allocated_max;
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unsigned long flags;
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ssize_t ret;
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ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
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if (kstrtouint(buf, 0, &uframe_periodic_max) < 0)
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return -EINVAL;
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if (uframe_periodic_max < 100 || uframe_periodic_max >= 125) {
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ehci_info(ehci, "rejecting invalid request for "
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"uframe_periodic_max=%u\n", uframe_periodic_max);
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return -EINVAL;
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}
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ret = -EINVAL;
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/*
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* lock, so that our checking does not race with possible periodic
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* bandwidth allocation through submitting new urbs.
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*/
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spin_lock_irqsave (&ehci->lock, flags);
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/*
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* for request to decrease max periodic bandwidth, we have to check
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* every microframe in the schedule to see whether the decrease is
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* possible.
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*/
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if (uframe_periodic_max < ehci->uframe_periodic_max) {
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allocated_max = 0;
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for (frame = 0; frame < ehci->periodic_size; ++frame)
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for (uframe = 0; uframe < 7; ++uframe)
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allocated_max = max(allocated_max,
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periodic_usecs (ehci, frame, uframe));
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if (allocated_max > uframe_periodic_max) {
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ehci_info(ehci,
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"cannot decrease uframe_periodic_max becase "
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"periodic bandwidth is already allocated "
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"(%u > %u)\n",
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allocated_max, uframe_periodic_max);
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goto out_unlock;
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}
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}
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/* increasing is always ok */
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ehci_info(ehci, "setting max periodic bandwidth to %u%% "
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"(== %u usec/uframe)\n",
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100*uframe_periodic_max/125, uframe_periodic_max);
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if (uframe_periodic_max != 100)
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ehci_warn(ehci, "max periodic bandwidth set is non-standard\n");
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ehci->uframe_periodic_max = uframe_periodic_max;
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ret = count;
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out_unlock:
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spin_unlock_irqrestore (&ehci->lock, flags);
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return ret;
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}
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static DEVICE_ATTR(uframe_periodic_max, 0644, show_uframe_periodic_max, store_uframe_periodic_max);
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static inline int create_sysfs_files(struct ehci_hcd *ehci)
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{
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struct device *controller = ehci_to_hcd(ehci)->self.controller;
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int i = 0;
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/* with integrated TT there is no companion! */
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if (!ehci_is_TDI(ehci))
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i = device_create_file(ehci_to_hcd(ehci)->self.controller,
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&dev_attr_companion);
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i = device_create_file(controller, &dev_attr_companion);
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if (i)
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goto out;
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i = device_create_file(controller, &dev_attr_uframe_periodic_max);
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out:
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return i;
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}
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static inline void remove_sysfs_files(struct ehci_hcd *ehci)
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{
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struct device *controller = ehci_to_hcd(ehci)->self.controller;
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/* with integrated TT there is no companion! */
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if (!ehci_is_TDI(ehci))
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device_remove_file(ehci_to_hcd(ehci)->self.controller,
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&dev_attr_companion);
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device_remove_file(controller, &dev_attr_companion);
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device_remove_file(controller, &dev_attr_uframe_periodic_max);
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}
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@ -87,6 +87,8 @@ struct ehci_hcd { /* one per controller */
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union ehci_shadow *pshadow; /* mirror hw periodic table */
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int next_uframe; /* scan periodic, start here */
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unsigned periodic_sched; /* periodic activity count */
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unsigned uframe_periodic_max; /* max periodic time per uframe */
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/* list of itds & sitds completed while clock_frame was still active */
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struct list_head cached_itd_list;
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