linux/drivers/usb/host/ehci-sysfs.c
Alan Stern d0ce5c6b92 USB: EHCI: use a bandwidth-allocation table
This patch significantly changes the scheduling code in ehci-hcd.
Instead of calculating the current bandwidth utilization by trudging
through the schedule and adding up the times used by the existing
transfers, we will now maintain a table holding the time used for each
of 64 microframes.  This will drastically speed up the bandwidth
computations.

In addition, it eliminates a theoretical bug.  An isochronous endpoint
may have bandwidth reserved even at times when it has no transfers
listed in the schedule.  The table will keep track of the reserved
bandwidth, whereas adding up entries in the schedule would miss it.

As a corollary, we can keep bandwidth reserved for endpoints even
when they aren't in active use.  Eventually the bandwidth will be
reserved when a new alternate setting is installed; for now the
endpoint's reservation takes place when its first URB is submitted.

A drawback of this approach is that transfers with an interval larger
than 64 microframes will have to be charged for bandwidth as though
the interval was 64.  In practice this shouldn't matter much;
transfers with longer intervals tend to be rather short anyway (things
like hubs or HID devices).

Another minor drawback is that we will keep track of two different
period and phase values: the actual ones and the ones used for
bandwidth allocation (which are limited to 64).  This adds only a
small amount of overhead: 3 bytes for each endpoint.

The patch also adds a new debugfs file named "bandwidth" to display
the information stored in the new table.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-10-11 16:45:43 -07:00

188 lines
5.1 KiB
C

/*
* Copyright (C) 2007 by Alan Stern
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/* this file is part of ehci-hcd.c */
/* Display the ports dedicated to the companion controller */
static ssize_t show_companion(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct ehci_hcd *ehci;
int nports, index, n;
int count = PAGE_SIZE;
char *ptr = buf;
ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
nports = HCS_N_PORTS(ehci->hcs_params);
for (index = 0; index < nports; ++index) {
if (test_bit(index, &ehci->companion_ports)) {
n = scnprintf(ptr, count, "%d\n", index + 1);
ptr += n;
count -= n;
}
}
return ptr - buf;
}
/*
* Dedicate or undedicate a port to the companion controller.
* Syntax is "[-]portnum", where a leading '-' sign means
* return control of the port to the EHCI controller.
*/
static ssize_t store_companion(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct ehci_hcd *ehci;
int portnum, new_owner;
ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
new_owner = PORT_OWNER; /* Owned by companion */
if (sscanf(buf, "%d", &portnum) != 1)
return -EINVAL;
if (portnum < 0) {
portnum = - portnum;
new_owner = 0; /* Owned by EHCI */
}
if (portnum <= 0 || portnum > HCS_N_PORTS(ehci->hcs_params))
return -ENOENT;
portnum--;
if (new_owner)
set_bit(portnum, &ehci->companion_ports);
else
clear_bit(portnum, &ehci->companion_ports);
set_owner(ehci, portnum, new_owner);
return count;
}
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 uframe;
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
* to see whether the decrease is possible.
*/
if (uframe_periodic_max < ehci->uframe_periodic_max) {
u8 allocated_max = 0;
for (uframe = 0; uframe < EHCI_BANDWIDTH_SIZE; ++uframe)
allocated_max = max(allocated_max,
ehci->bandwidth[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(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(controller, &dev_attr_companion);
device_remove_file(controller, &dev_attr_uframe_periodic_max);
}