forked from Minki/linux
df2022553d
This patch (as1577) adds hrtimer support for unlinking interrupt QHs in ehci-hcd. The current code relies on a fixed delay of either 2 or 55 us, which is not always adequate and in any case is totally bogus. Thanks to internal caching, the EHCI hardware may continue to access an interrupt QH for more than a millisecond after it has been unlinked. In fact, the EHCI spec doesn't say how long to wait before using an unlinked interrupt QH. The patch sets the delay to 9 microframes minimum, which ought to be adequate. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
270 lines
8.1 KiB
C
270 lines
8.1 KiB
C
/*
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* Copyright (C) 2012 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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/* This file is part of ehci-hcd.c */
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/*-------------------------------------------------------------------------*/
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/* Set a bit in the USBCMD register */
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static void ehci_set_command_bit(struct ehci_hcd *ehci, u32 bit)
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{
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ehci->command |= bit;
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ehci_writel(ehci, ehci->command, &ehci->regs->command);
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/* unblock posted write */
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ehci_readl(ehci, &ehci->regs->command);
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}
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/* Clear a bit in the USBCMD register */
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static void ehci_clear_command_bit(struct ehci_hcd *ehci, u32 bit)
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{
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ehci->command &= ~bit;
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ehci_writel(ehci, ehci->command, &ehci->regs->command);
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/* unblock posted write */
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ehci_readl(ehci, &ehci->regs->command);
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}
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/*-------------------------------------------------------------------------*/
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/*
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* EHCI timer support... Now using hrtimers.
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*
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* Lots of different events are triggered from ehci->hrtimer. Whenever
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* the timer routine runs, it checks each possible event; events that are
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* currently enabled and whose expiration time has passed get handled.
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* The set of enabled events is stored as a collection of bitflags in
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* ehci->enabled_hrtimer_events, and they are numbered in order of
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* increasing delay values (ranging between 1 ms and 100 ms).
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*
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* Rather than implementing a sorted list or tree of all pending events,
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* we keep track only of the lowest-numbered pending event, in
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* ehci->next_hrtimer_event. Whenever ehci->hrtimer gets restarted, its
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* expiration time is set to the timeout value for this event.
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*
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* As a result, events might not get handled right away; the actual delay
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* could be anywhere up to twice the requested delay. This doesn't
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* matter, because none of the events are especially time-critical. The
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* ones that matter most all have a delay of 1 ms, so they will be
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* handled after 2 ms at most, which is okay. In addition to this, we
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* allow for an expiration range of 1 ms.
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*/
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/*
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* Delay lengths for the hrtimer event types.
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* Keep this list sorted by delay length, in the same order as
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* the event types indexed by enum ehci_hrtimer_event in ehci.h.
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*/
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static unsigned event_delays_ns[] = {
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1 * NSEC_PER_MSEC, /* EHCI_HRTIMER_POLL_ASS */
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1 * NSEC_PER_MSEC, /* EHCI_HRTIMER_POLL_PSS */
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1125 * NSEC_PER_USEC, /* EHCI_HRTIMER_UNLINK_INTR */
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10 * NSEC_PER_MSEC, /* EHCI_HRTIMER_DISABLE_PERIODIC */
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15 * NSEC_PER_MSEC, /* EHCI_HRTIMER_DISABLE_ASYNC */
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};
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/* Enable a pending hrtimer event */
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static void ehci_enable_event(struct ehci_hcd *ehci, unsigned event,
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bool resched)
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{
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ktime_t *timeout = &ehci->hr_timeouts[event];
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if (resched)
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*timeout = ktime_add(ktime_get(),
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ktime_set(0, event_delays_ns[event]));
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ehci->enabled_hrtimer_events |= (1 << event);
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/* Track only the lowest-numbered pending event */
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if (event < ehci->next_hrtimer_event) {
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ehci->next_hrtimer_event = event;
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hrtimer_start_range_ns(&ehci->hrtimer, *timeout,
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NSEC_PER_MSEC, HRTIMER_MODE_ABS);
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}
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}
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/* Poll the STS_ASS status bit; see when it agrees with CMD_ASE */
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static void ehci_poll_ASS(struct ehci_hcd *ehci)
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{
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unsigned actual, want;
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/* Don't enable anything if the controller isn't running (e.g., died) */
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if (ehci->rh_state != EHCI_RH_RUNNING)
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return;
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want = (ehci->command & CMD_ASE) ? STS_ASS : 0;
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actual = ehci_readl(ehci, &ehci->regs->status) & STS_ASS;
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if (want != actual) {
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/* Poll again later, but give up after about 20 ms */
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if (ehci->ASS_poll_count++ < 20) {
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ehci_enable_event(ehci, EHCI_HRTIMER_POLL_ASS, true);
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return;
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}
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ehci_warn(ehci, "Waited too long for the async schedule status, giving up\n");
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}
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ehci->ASS_poll_count = 0;
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/* The status is up-to-date; restart or stop the schedule as needed */
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if (want == 0) { /* Stopped */
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if (ehci->async_count > 0)
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ehci_set_command_bit(ehci, CMD_ASE);
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} else { /* Running */
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if (ehci->async_count == 0) {
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/* Turn off the schedule after a while */
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ehci_enable_event(ehci, EHCI_HRTIMER_DISABLE_ASYNC,
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true);
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}
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}
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}
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/* Turn off the async schedule after a brief delay */
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static void ehci_disable_ASE(struct ehci_hcd *ehci)
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{
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ehci_clear_command_bit(ehci, CMD_ASE);
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}
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/* Poll the STS_PSS status bit; see when it agrees with CMD_PSE */
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static void ehci_poll_PSS(struct ehci_hcd *ehci)
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{
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unsigned actual, want;
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/* Don't do anything if the controller isn't running (e.g., died) */
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if (ehci->rh_state != EHCI_RH_RUNNING)
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return;
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want = (ehci->command & CMD_PSE) ? STS_PSS : 0;
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actual = ehci_readl(ehci, &ehci->regs->status) & STS_PSS;
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if (want != actual) {
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/* Poll again later, but give up after about 20 ms */
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if (ehci->PSS_poll_count++ < 20) {
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ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
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return;
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}
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ehci_warn(ehci, "Waited too long for the periodic schedule status, giving up\n");
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}
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ehci->PSS_poll_count = 0;
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/* The status is up-to-date; restart or stop the schedule as needed */
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if (want == 0) { /* Stopped */
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free_cached_lists(ehci);
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if (ehci->periodic_count > 0) {
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/* make sure ehci_work scans these */
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ehci->next_uframe = ehci_read_frame_index(ehci)
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& ((ehci->periodic_size << 3) - 1);
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ehci_set_command_bit(ehci, CMD_PSE);
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}
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} else { /* Running */
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if (ehci->periodic_count == 0) {
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/* Turn off the schedule after a while */
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ehci_enable_event(ehci, EHCI_HRTIMER_DISABLE_PERIODIC,
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true);
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}
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}
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}
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/* Turn off the periodic schedule after a brief delay */
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static void ehci_disable_PSE(struct ehci_hcd *ehci)
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{
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ehci_clear_command_bit(ehci, CMD_PSE);
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/* Poll to see when it actually stops */
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ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
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}
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/* Handle unlinked interrupt QHs once they are gone from the hardware */
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static void ehci_handle_intr_unlinks(struct ehci_hcd *ehci)
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{
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bool stopped = (ehci->rh_state < EHCI_RH_RUNNING);
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/*
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* Process all the QHs on the intr_unlink list that were added
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* before the current unlink cycle began. The list is in
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* temporal order, so stop when we reach the first entry in the
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* current cycle. But if the root hub isn't running then
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* process all the QHs on the list.
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*/
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ehci->intr_unlinking = true;
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while (ehci->intr_unlink) {
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struct ehci_qh *qh = ehci->intr_unlink;
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if (!stopped && qh->unlink_cycle == ehci->intr_unlink_cycle)
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break;
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ehci->intr_unlink = qh->unlink_next;
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qh->unlink_next = NULL;
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end_unlink_intr(ehci, qh);
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}
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/* Handle remaining entries later */
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if (ehci->intr_unlink) {
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ehci_enable_event(ehci, EHCI_HRTIMER_UNLINK_INTR, true);
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++ehci->intr_unlink_cycle;
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}
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ehci->intr_unlinking = false;
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}
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/*
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* Handler functions for the hrtimer event types.
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* Keep this array in the same order as the event types indexed by
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* enum ehci_hrtimer_event in ehci.h.
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*/
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static void (*event_handlers[])(struct ehci_hcd *) = {
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ehci_poll_ASS, /* EHCI_HRTIMER_POLL_ASS */
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ehci_poll_PSS, /* EHCI_HRTIMER_POLL_PSS */
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ehci_handle_intr_unlinks, /* EHCI_HRTIMER_UNLINK_INTR */
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ehci_disable_PSE, /* EHCI_HRTIMER_DISABLE_PERIODIC */
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ehci_disable_ASE, /* EHCI_HRTIMER_DISABLE_ASYNC */
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};
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static enum hrtimer_restart ehci_hrtimer_func(struct hrtimer *t)
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{
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struct ehci_hcd *ehci = container_of(t, struct ehci_hcd, hrtimer);
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ktime_t now;
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unsigned long events;
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unsigned long flags;
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unsigned e;
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spin_lock_irqsave(&ehci->lock, flags);
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events = ehci->enabled_hrtimer_events;
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ehci->enabled_hrtimer_events = 0;
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ehci->next_hrtimer_event = EHCI_HRTIMER_NO_EVENT;
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/*
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* Check each pending event. If its time has expired, handle
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* the event; otherwise re-enable it.
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*/
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now = ktime_get();
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for_each_set_bit(e, &events, EHCI_HRTIMER_NUM_EVENTS) {
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if (now.tv64 >= ehci->hr_timeouts[e].tv64)
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event_handlers[e](ehci);
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else
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ehci_enable_event(ehci, e, false);
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}
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spin_unlock_irqrestore(&ehci->lock, flags);
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return HRTIMER_NORESTART;
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}
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