/*
 * 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 */
	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 20 ms */
		if (ehci->ASS_poll_count++ < 20) {
			ehci_enable_event(ehci, EHCI_HRTIMER_POLL_ASS, true);
			return;
		}
		ehci_warn(ehci, "Waited too long for the async schedule status, giving up\n");
	}
	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 20 ms */
		if (ehci->PSS_poll_count++ < 20) {
			ehci_enable_event(ehci, EHCI_HRTIMER_POLL_PSS, true);
			return;
		}
		ehci_warn(ehci, "Waited too long for the periodic schedule status, giving up\n");
	}
	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\n");
	}

	/* 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 */
}


/* 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 (ehci->intr_unlink) {
		struct ehci_qh	*qh = ehci->intr_unlink;

		if (!stopped && qh->unlink_cycle == ehci->intr_unlink_cycle)
			break;
		ehci->intr_unlink = qh->unlink_next;
		qh->unlink_next = NULL;
		end_unlink_intr(ehci, qh);
	}

	/* Handle remaining entries later */
	if (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)
{
	if (ehci->rh_state != EHCI_RH_RUNNING)
		return;

	/*
	 * 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->async_iaa) {
		u32 cmd, status;

		/* 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_vdbg(ehci, "IAA watchdog: status %x cmd %x\n",
				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 */
	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;
}