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![Kirill Smelkov](/assets/img/avatar_default.png)
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>
190 lines
5.2 KiB
C
190 lines
5.2 KiB
C
/*
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* Copyright (C) 2007 by Alan Stern
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/* this file is part of ehci-hcd.c */
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/* Display the ports dedicated to the companion controller */
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static ssize_t show_companion(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 nports, index, n;
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int count = PAGE_SIZE;
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char *ptr = buf;
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ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
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nports = HCS_N_PORTS(ehci->hcs_params);
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for (index = 0; index < nports; ++index) {
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if (test_bit(index, &ehci->companion_ports)) {
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n = scnprintf(ptr, count, "%d\n", index + 1);
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ptr += n;
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count -= n;
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}
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}
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return ptr - buf;
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}
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/*
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* Dedicate or undedicate a port to the companion controller.
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* Syntax is "[-]portnum", where a leading '-' sign means
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* return control of the port to the EHCI controller.
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*/
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static ssize_t store_companion(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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int portnum, new_owner;
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ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
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new_owner = PORT_OWNER; /* Owned by companion */
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if (sscanf(buf, "%d", &portnum) != 1)
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return -EINVAL;
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if (portnum < 0) {
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portnum = - portnum;
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new_owner = 0; /* Owned by EHCI */
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}
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if (portnum <= 0 || portnum > HCS_N_PORTS(ehci->hcs_params))
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return -ENOENT;
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portnum--;
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if (new_owner)
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set_bit(portnum, &ehci->companion_ports);
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else
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clear_bit(portnum, &ehci->companion_ports);
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set_owner(ehci, portnum, new_owner);
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return count;
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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(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(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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