/*
   * Copyright (C) 2012 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.
   */
  
  /* This file is part of ehci-hcd.c */
  
  /*-------------------------------------------------------------------------*/
  
  /* Set a bit in the USBCMD register */
  static void ehci_set_command_bit(struct ehci_hcd *ehci, u32 bit)
  {
  	ehci->command |= bit;
  	ehci_writel(ehci, ehci->command, &ehci->regs->command);
  
  	/* unblock posted write */
  	ehci_readl(ehci, &ehci->regs->command);
  }
  
  /* Clear a bit in the USBCMD register */
  static void ehci_clear_command_bit(struct ehci_hcd *ehci, u32 bit)
  {
  	ehci->command &= ~bit;
  	ehci_writel(ehci, ehci->command, &ehci->regs->command);
  
  	/* unblock posted write */
  	ehci_readl(ehci, &ehci->regs->command);
  }
  
  /*-------------------------------------------------------------------------*/
  
  /*
   * EHCI timer support...  Now using hrtimers.
   *
   * Lots of different events are triggered from ehci->hrtimer.  Whenever
   * the timer routine runs, it checks each possible event; events that are
   * currently enabled and whose expiration time has passed get handled.
   * The set of enabled events is stored as a collection of bitflags in
   * ehci->enabled_hrtimer_events, and they are numbered in order of
   * increasing delay values (ranging between 1 ms and 100 ms).
   *
   * Rather than implementing a sorted list or tree of all pending events,
   * we keep track only of the lowest-numbered pending event, in
   * ehci->next_hrtimer_event.  Whenever ehci->hrtimer gets restarted, its
   * expiration time is set to the timeout value for this event.
   *
   * As a result, events might not get handled right away; the actual delay
   * could be anywhere up to twice the requested delay.  This doesn't
   * matter, because none of the events are especially time-critical.  The
   * ones that matter most all have a delay of 1 ms, so they will be
   * handled after 2 ms at most, which is okay.  In addition to this, we
   * allow for an expiration range of 1 ms.
   */
  
  /*
   * Delay lengths for the hrtimer event types.
   * Keep this list sorted by delay length, in the same order as
   * the event types indexed by enum ehci_hrtimer_event in ehci.h.
   */
  static unsigned event_delays_ns[] = {
  	1 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_POLL_ASS */
  	1 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_POLL_PSS */
  	1 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_POLL_DEAD */
  	1125 * NSEC_PER_USEC,	/* EHCI_HRTIMER_UNLINK_INTR */
  	2 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_FREE_ITDS */
  	5 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_START_UNLINK_INTR */
  	6 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_ASYNC_UNLINKS */
  	10 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_IAA_WATCHDOG */
  	10 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_DISABLE_PERIODIC */
  	15 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_DISABLE_ASYNC */
  	100 * NSEC_PER_MSEC,	/* EHCI_HRTIMER_IO_WATCHDOG */
  };
  
  /* Enable a pending hrtimer event */
  static void ehci_enable_event(struct ehci_hcd *ehci, unsigned event,
  		bool resched)
  {
  	ktime_t		*timeout = &ehci->hr_timeouts[event];
  
  	if (resched)
  		*timeout = ktime_add(ktime_get(),
  				ktime_set(0, event_delays_ns[event]));
  	ehci->enabled_hrtimer_events |= (1 << event);
  
  	/* Track only the lowest-numbered pending event */
  	if (event < ehci->next_hrtimer_event) {
  		ehci->next_hrtimer_event = event;
  		hrtimer_start_range_ns(&ehci->hrtimer, *timeout,
  				NSEC_PER_MSEC, HRTIMER_MODE_ABS);
  	}
  }
  
  
  /* Poll the STS_ASS status bit; see when it agrees with CMD_ASE */
  static void ehci_poll_ASS(struct ehci_hcd *ehci)
  {
  	unsigned	actual, want;
  
  	/* Don't enable anything if the controller isn't running (e.g., died) */
  	if (ehci->rh_state != EHCI_RH_RUNNING)
  		return;
  
  	want = (ehci->command & CMD_ASE) ? STS_ASS : 0;
  	actual = ehci_readl(ehci, &ehci->regs->status) & STS_ASS;
  
  	if (want != actual) {
  
  		/* Poll again later, but give up after about 2-4 ms */
  		if (ehci->ASS_poll_count++ < 2) {
  			ehci_enable_event(ehci, EHCI_HRTIMER_POLL_ASS, true);
  			return;
  		}
  		ehci_dbg(ehci, "Waited too long for the async schedule status (%x/%x), giving up
  ",
  				want, actual);
  	}
  	ehci->ASS_poll_count = 0;
  
  	/* The status is up-to-date; restart or stop the schedule as needed */
  	if (want == 0) {	/* Stopped */
  		if (ehci->async_count > 0)
  			ehci_set_command_bit(ehci, CMD_ASE);
  
  	} else {		/* Running */
  		if (ehci->async_count == 0) {
  
  			/* Turn off the schedule after a while */
  			ehci_enable_event(ehci, EHCI_HRTIMER_DISABLE_ASYNC,
  					true);
  		}
  	}
  }
  
  /* Turn off the async schedule after a brief delay */
  static void ehci_disable_ASE(struct ehci_hcd *ehci)
  {
  	ehci_clear_command_bit(ehci, CMD_ASE);
  }
  
  
  /* Poll the STS_PSS status bit; see when it agrees with CMD_PSE */
  static void ehci_poll_PSS(struct ehci_hcd *ehci)
  {
  	unsigned	actual, want;
  
  	/* Don't do anything if the controller isn't running (e.g., died) */
  	if (ehci->rh_state != EHCI_RH_RUNNING)
  		return;
  
  	want = (ehci->command & CMD_PSE) ? STS_PSS : 0;
  	actual = ehci_readl(ehci, &ehci->regs->status) & STS_PSS;
  
  	if (want != actual) {
  
  		/* Poll again later, but give up after about 2-4 ms */
  		if (ehci->PSS_poll_count++ < 2) {
  			ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
  			return;
  		}
  		ehci_dbg(ehci, "Waited too long for the periodic schedule status (%x/%x), giving up
  ",
  				want, actual);
  	}
  	ehci->PSS_poll_count = 0;
  
  	/* The status is up-to-date; restart or stop the schedule as needed */
  	if (want == 0) {	/* Stopped */
  		if (ehci->periodic_count > 0)
  			ehci_set_command_bit(ehci, CMD_PSE);
  
  	} else {		/* Running */
  		if (ehci->periodic_count == 0) {
  
  			/* Turn off the schedule after a while */
  			ehci_enable_event(ehci, EHCI_HRTIMER_DISABLE_PERIODIC,
  					true);
  		}
  	}
  }
  
  /* Turn off the periodic schedule after a brief delay */
  static void ehci_disable_PSE(struct ehci_hcd *ehci)
  {
  	ehci_clear_command_bit(ehci, CMD_PSE);
  }
  
  
  /* Poll the STS_HALT status bit; see when a dead controller stops */
  static void ehci_handle_controller_death(struct ehci_hcd *ehci)
  {
  	if (!(ehci_readl(ehci, &ehci->regs->status) & STS_HALT)) {
  
  		/* Give up after a few milliseconds */
  		if (ehci->died_poll_count++ < 5) {
  			/* Try again later */
  			ehci_enable_event(ehci, EHCI_HRTIMER_POLL_DEAD, true);
  			return;
  		}
  		ehci_warn(ehci, "Waited too long for the controller to stop, giving up
  ");
  	}
  
  	/* Clean up the mess */
  	ehci->rh_state = EHCI_RH_HALTED;
  	ehci_writel(ehci, 0, &ehci->regs->configured_flag);
  	ehci_writel(ehci, 0, &ehci->regs->intr_enable);
  	ehci_work(ehci);
  	end_unlink_async(ehci);
  
  	/* Not in process context, so don't try to reset the controller */
  }
  
  /* start to unlink interrupt QHs  */
  static void ehci_handle_start_intr_unlinks(struct ehci_hcd *ehci)
  {
  	bool		stopped = (ehci->rh_state < EHCI_RH_RUNNING);
  
  	/*
  	 * Process all the QHs on the intr_unlink list that were added
  	 * before the current unlink cycle began.  The list is in
  	 * temporal order, so stop when we reach the first entry in the
  	 * current cycle.  But if the root hub isn't running then
  	 * process all the QHs on the list.
  	 */
  	while (!list_empty(&ehci->intr_unlink_wait)) {
  		struct ehci_qh	*qh;
  
  		qh = list_first_entry(&ehci->intr_unlink_wait,
  				struct ehci_qh, unlink_node);
  		if (!stopped && (qh->unlink_cycle ==
  				ehci->intr_unlink_wait_cycle))
  			break;
  		list_del_init(&qh->unlink_node);
  		start_unlink_intr(ehci, qh);
  	}
  
  	/* Handle remaining entries later */
  	if (!list_empty(&ehci->intr_unlink_wait)) {
  		ehci_enable_event(ehci, EHCI_HRTIMER_START_UNLINK_INTR, true);
  		++ehci->intr_unlink_wait_cycle;
  	}
  }
  
  /* Handle unlinked interrupt QHs once they are gone from the hardware */
  static void ehci_handle_intr_unlinks(struct ehci_hcd *ehci)
  {
  	bool		stopped = (ehci->rh_state < EHCI_RH_RUNNING);
  
  	/*
  	 * Process all the QHs on the intr_unlink list that were added
  	 * before the current unlink cycle began.  The list is in
  	 * temporal order, so stop when we reach the first entry in the
  	 * current cycle.  But if the root hub isn't running then
  	 * process all the QHs on the list.
  	 */
  	ehci->intr_unlinking = true;
  	while (!list_empty(&ehci->intr_unlink)) {
  		struct ehci_qh	*qh;
  
  		qh = list_first_entry(&ehci->intr_unlink, struct ehci_qh,
  				unlink_node);
  		if (!stopped && qh->unlink_cycle == ehci->intr_unlink_cycle)
  			break;
  		list_del_init(&qh->unlink_node);
  		end_unlink_intr(ehci, qh);
  	}
  
  	/* Handle remaining entries later */
  	if (!list_empty(&ehci->intr_unlink)) {
  		ehci_enable_event(ehci, EHCI_HRTIMER_UNLINK_INTR, true);
  		++ehci->intr_unlink_cycle;
  	}
  	ehci->intr_unlinking = false;
  }
  
  
  /* Start another free-iTDs/siTDs cycle */
  static void start_free_itds(struct ehci_hcd *ehci)
  {
  	if (!(ehci->enabled_hrtimer_events & BIT(EHCI_HRTIMER_FREE_ITDS))) {
  		ehci->last_itd_to_free = list_entry(
  				ehci->cached_itd_list.prev,
  				struct ehci_itd, itd_list);
  		ehci->last_sitd_to_free = list_entry(
  				ehci->cached_sitd_list.prev,
  				struct ehci_sitd, sitd_list);
  		ehci_enable_event(ehci, EHCI_HRTIMER_FREE_ITDS, true);
  	}
  }
  
  /* Wait for controller to stop using old iTDs and siTDs */
  static void end_free_itds(struct ehci_hcd *ehci)
  {
  	struct ehci_itd		*itd, *n;
  	struct ehci_sitd	*sitd, *sn;
  
  	if (ehci->rh_state < EHCI_RH_RUNNING) {
  		ehci->last_itd_to_free = NULL;
  		ehci->last_sitd_to_free = NULL;
  	}
  
  	list_for_each_entry_safe(itd, n, &ehci->cached_itd_list, itd_list) {
  		list_del(&itd->itd_list);
  		dma_pool_free(ehci->itd_pool, itd, itd->itd_dma);
  		if (itd == ehci->last_itd_to_free)
  			break;
  	}
  	list_for_each_entry_safe(sitd, sn, &ehci->cached_sitd_list, sitd_list) {
  		list_del(&sitd->sitd_list);
  		dma_pool_free(ehci->sitd_pool, sitd, sitd->sitd_dma);
  		if (sitd == ehci->last_sitd_to_free)
  			break;
  	}
  
  	if (!list_empty(&ehci->cached_itd_list) ||
  			!list_empty(&ehci->cached_sitd_list))
  		start_free_itds(ehci);
  }
  
  
  /* Handle lost (or very late) IAA interrupts */
  static void ehci_iaa_watchdog(struct ehci_hcd *ehci)
  {
  	u32 cmd, status;
  
  	/*
  	 * Lost IAA irqs wedge things badly; seen first with a vt8235.
  	 * So we need this watchdog, but must protect it against both
  	 * (a) SMP races against real IAA firing and retriggering, and
  	 * (b) clean HC shutdown, when IAA watchdog was pending.
  	 */
  	if (!ehci->iaa_in_progress || ehci->rh_state != EHCI_RH_RUNNING)
  		return;
  
  	/* If we get here, IAA is *REALLY* late.  It's barely
  	 * conceivable that the system is so busy that CMD_IAAD
  	 * is still legitimately set, so let's be sure it's
  	 * clear before we read STS_IAA.  (The HC should clear
  	 * CMD_IAAD when it sets STS_IAA.)
  	 */
  	cmd = ehci_readl(ehci, &ehci->regs->command);
  
  	/*
  	 * If IAA is set here it either legitimately triggered
  	 * after the watchdog timer expired (_way_ late, so we'll
  	 * still count it as lost) ... or a silicon erratum:
  	 * - VIA seems to set IAA without triggering the IRQ;
  	 * - IAAD potentially cleared without setting IAA.
  	 */
  	status = ehci_readl(ehci, &ehci->regs->status);
  	if ((status & STS_IAA) || !(cmd & CMD_IAAD)) {
  		COUNT(ehci->stats.lost_iaa);
  		ehci_writel(ehci, STS_IAA, &ehci->regs->status);
  	}
  
  	ehci_dbg(ehci, "IAA watchdog: status %x cmd %x
  ", status, cmd);
  	end_unlink_async(ehci);
  }
  
  
  /* Enable the I/O watchdog, if appropriate */
  static void turn_on_io_watchdog(struct ehci_hcd *ehci)
  {
  	/* Not needed if the controller isn't running or it's already enabled */
  	if (ehci->rh_state != EHCI_RH_RUNNING ||
  			(ehci->enabled_hrtimer_events &
  				BIT(EHCI_HRTIMER_IO_WATCHDOG)))
  		return;
  
  	/*
  	 * Isochronous transfers always need the watchdog.
  	 * For other sorts we use it only if the flag is set.
  	 */
  	if (ehci->isoc_count > 0 || (ehci->need_io_watchdog &&
  			ehci->async_count + ehci->intr_count > 0))
  		ehci_enable_event(ehci, EHCI_HRTIMER_IO_WATCHDOG, true);
  }
  
  
  /*
   * Handler functions for the hrtimer event types.
   * Keep this array in the same order as the event types indexed by
   * enum ehci_hrtimer_event in ehci.h.
   */
  static void (*event_handlers[])(struct ehci_hcd *) = {
  	ehci_poll_ASS,			/* EHCI_HRTIMER_POLL_ASS */
  	ehci_poll_PSS,			/* EHCI_HRTIMER_POLL_PSS */
  	ehci_handle_controller_death,	/* EHCI_HRTIMER_POLL_DEAD */
  	ehci_handle_intr_unlinks,	/* EHCI_HRTIMER_UNLINK_INTR */
  	end_free_itds,			/* EHCI_HRTIMER_FREE_ITDS */
  	ehci_handle_start_intr_unlinks,	/* EHCI_HRTIMER_START_UNLINK_INTR */
  	unlink_empty_async,		/* EHCI_HRTIMER_ASYNC_UNLINKS */
  	ehci_iaa_watchdog,		/* EHCI_HRTIMER_IAA_WATCHDOG */
  	ehci_disable_PSE,		/* EHCI_HRTIMER_DISABLE_PERIODIC */
  	ehci_disable_ASE,		/* EHCI_HRTIMER_DISABLE_ASYNC */
  	ehci_work,			/* EHCI_HRTIMER_IO_WATCHDOG */
  };
  
  static enum hrtimer_restart ehci_hrtimer_func(struct hrtimer *t)
  {
  	struct ehci_hcd	*ehci = container_of(t, struct ehci_hcd, hrtimer);
  	ktime_t		now;
  	unsigned long	events;
  	unsigned long	flags;
  	unsigned	e;
  
  	spin_lock_irqsave(&ehci->lock, flags);
  
  	events = ehci->enabled_hrtimer_events;
  	ehci->enabled_hrtimer_events = 0;
  	ehci->next_hrtimer_event = EHCI_HRTIMER_NO_EVENT;
  
  	/*
  	 * Check each pending event.  If its time has expired, handle
  	 * the event; otherwise re-enable it.
  	 */
  	now = ktime_get();
  	for_each_set_bit(e, &events, EHCI_HRTIMER_NUM_EVENTS) {
  		if (now.tv64 >= ehci->hr_timeouts[e].tv64)
  			event_handlers[e](ehci);
  		else
  			ehci_enable_event(ehci, e, false);
  	}
  
  	spin_unlock_irqrestore(&ehci->lock, flags);
  	return HRTIMER_NORESTART;
  }