xref: /linux/drivers/thunderbolt/nhi.c (revision 7db28abbea0f7dc1ec4fdfdc149db5fbd9e4c994)

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Thunderbolt driver - NHI driver
 *
 * The NHI (native host interface) is the device that allows us to send and
 * receive frames from the thunderbolt bus.
 *
 * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
 * Copyright (C) 2018, Intel Corporation
 */

#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/iommu.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/property.h>
#include <linux/string_choices.h>
#include <linux/string_helpers.h>

#include "nhi.h"
#include "nhi_regs.h"
#include "tb.h"

#define RING_TYPE(ring) ((ring)->is_tx ? "TX ring" : "RX ring")

#define RING_FIRST_USABLE_HOPID	1
/*
 * Used with QUIRK_E2E to specify an unused HopID the Rx credits are
 * transferred.
 */
#define RING_E2E_RESERVED_HOPID	RING_FIRST_USABLE_HOPID

#define NHI_MAILBOX_TIMEOUT	500 /* ms */

static bool host_reset = true;
module_param(host_reset, bool, 0444);
MODULE_PARM_DESC(host_reset, "reset USB4 host router (default: true)");

static int ring_interrupt_index(const struct tb_ring *ring)
{
	int bit = ring->hop;
	if (!ring->is_tx)
		bit += ring->nhi->hop_count;
	return bit;
}

static void nhi_mask_interrupt(struct tb_nhi *nhi, int mask, int ring)
{
	if (nhi->quirks & QUIRK_AUTO_CLEAR_INT) {
		u32 val;

		val = ioread32(nhi->iobase + REG_RING_INTERRUPT_BASE + ring);
		iowrite32(val & ~mask, nhi->iobase + REG_RING_INTERRUPT_BASE + ring);
	} else {
		iowrite32(mask, nhi->iobase + REG_RING_INTERRUPT_MASK_CLEAR_BASE + ring);
	}
}

static void nhi_clear_interrupt(struct tb_nhi *nhi, int ring)
{
	if (nhi->quirks & QUIRK_AUTO_CLEAR_INT)
		ioread32(nhi->iobase + REG_RING_NOTIFY_BASE + ring);
	else
		iowrite32(~0, nhi->iobase + REG_RING_INT_CLEAR + ring);
}

/*
 * ring_interrupt_active() - activate/deactivate interrupts for a single ring
 *
 * ring->nhi->lock must be held.
 */
static void ring_interrupt_active(struct tb_ring *ring, bool active)
{
	int index = ring_interrupt_index(ring) / 32 * 4;
	int reg = REG_RING_INTERRUPT_BASE + index;
	int interrupt_bit = ring_interrupt_index(ring) & 31;
	int mask = 1 << interrupt_bit;
	u32 old, new;

	if (ring->irq > 0) {
		u32 step, shift, ivr, misc, itr;
		void __iomem *ivr_base;
		int auto_clear_bit;
		int index;

		if (ring->is_tx)
			index = ring->hop;
		else
			index = ring->hop + ring->nhi->hop_count;

		/*
		 * Intel routers support a bit that isn't part of
		 * the USB4 spec to ask the hardware to clear
		 * interrupt status bits automatically since
		 * we already know which interrupt was triggered.
		 *
		 * Other routers explicitly disable auto-clear
		 * to prevent conditions that may occur where two
		 * MSIX interrupts are simultaneously active and
		 * reading the register clears both of them.
		 */
		misc = ioread32(ring->nhi->iobase + REG_DMA_MISC);
		if (ring->nhi->quirks & QUIRK_AUTO_CLEAR_INT)
			auto_clear_bit = REG_DMA_MISC_INT_AUTO_CLEAR;
		else
			auto_clear_bit = REG_DMA_MISC_DISABLE_AUTO_CLEAR;
		if (!(misc & auto_clear_bit))
			iowrite32(misc | auto_clear_bit,
				  ring->nhi->iobase + REG_DMA_MISC);

		ivr_base = ring->nhi->iobase + REG_INT_VEC_ALLOC_BASE;
		step = index / REG_INT_VEC_ALLOC_REGS * REG_INT_VEC_ALLOC_BITS;
		shift = index % REG_INT_VEC_ALLOC_REGS * REG_INT_VEC_ALLOC_BITS;
		ivr = ioread32(ivr_base + step);
		ivr &= ~(REG_INT_VEC_ALLOC_MASK << shift);
		if (active)
			ivr |= ring->vector << shift;
		iowrite32(ivr, ivr_base + step);

		/* Throttling is specified in 256ns increments */
		itr = DIV_ROUND_UP(ring->interval_nsec, 256);
		itr &= REG_INT_THROTTLING_RATE_INTERVAL_MASK;
		iowrite32(itr, ring->nhi->iobase + REG_INT_THROTTLING_RATE +
			  ring->vector * 4);
	}

	old = ioread32(ring->nhi->iobase + reg);
	if (active)
		new = old | mask;
	else
		new = old & ~mask;

	dev_dbg(ring->nhi->dev,
		"%s interrupt at register %#x bit %d (%#x -> %#x)\n",
		active ? "enabling" : "disabling", reg, interrupt_bit, old, new);

	if (new == old)
		dev_WARN(ring->nhi->dev, "interrupt for %s %d is already %s\n",
			 RING_TYPE(ring), ring->hop,
			 str_enabled_disabled(active));

	if (active)
		iowrite32(new, ring->nhi->iobase + reg);
	else
		nhi_mask_interrupt(ring->nhi, mask, index);
}

/*
 * nhi_disable_interrupts() - disable interrupts for all rings
 *
 * Use only during init and shutdown.
 */
void nhi_disable_interrupts(struct tb_nhi *nhi)
{
	int i = 0;
	/* disable interrupts */
	for (i = 0; i < RING_INTERRUPT_REG_COUNT(nhi); i++)
		nhi_mask_interrupt(nhi, ~0, 4 * i);

	/* clear interrupt status bits */
	for (i = 0; i < RING_NOTIFY_REG_COUNT(nhi); i++)
		nhi_clear_interrupt(nhi, 4 * i);
}

/* ring helper methods */

static void __iomem *ring_desc_base(struct tb_ring *ring)
{
	void __iomem *io = ring->nhi->iobase;
	io += ring->is_tx ? REG_TX_RING_BASE : REG_RX_RING_BASE;
	io += ring->hop * 16;
	return io;
}

static void __iomem *ring_options_base(struct tb_ring *ring)
{
	void __iomem *io = ring->nhi->iobase;
	io += ring->is_tx ? REG_TX_OPTIONS_BASE : REG_RX_OPTIONS_BASE;
	io += ring->hop * 32;
	return io;
}

static void ring_iowrite_cons(struct tb_ring *ring, u16 cons)
{
	/*
	 * The other 16-bits in the register is read-only and writes to it
	 * are ignored by the hardware so we can save one ioread32() by
	 * filling the read-only bits with zeroes.
	 */
	iowrite32(cons, ring_desc_base(ring) + 8);
}

static void ring_iowrite_prod(struct tb_ring *ring, u16 prod)
{
	/* See ring_iowrite_cons() above for explanation */
	iowrite32(prod << 16, ring_desc_base(ring) + 8);
}

static void ring_iowrite32desc(struct tb_ring *ring, u32 value, u32 offset)
{
	iowrite32(value, ring_desc_base(ring) + offset);
}

static void ring_iowrite64desc(struct tb_ring *ring, u64 value, u32 offset)
{
	iowrite32(value, ring_desc_base(ring) + offset);
	iowrite32(value >> 32, ring_desc_base(ring) + offset + 4);
}

static void ring_iowrite32options(struct tb_ring *ring, u32 value, u32 offset)
{
	iowrite32(value, ring_options_base(ring) + offset);
}

static bool ring_full(struct tb_ring *ring)
{
	return ((ring->head + 1) % ring->size) == ring->tail;
}

static bool ring_empty(struct tb_ring *ring)
{
	return ring->head == ring->tail;
}

/*
 * ring_write_descriptors() - post frames from ring->queue to the controller
 *
 * ring->lock is held.
 */
static void ring_write_descriptors(struct tb_ring *ring)
{
	struct ring_frame *frame, *n;
	struct ring_desc *descriptor;
	u32 flags;

	flags = RING_DESC_POSTED;
	if (!(ring->flags & RING_FLAG_NO_INTERRUPT))
		flags |= RING_DESC_INTERRUPT;

	list_for_each_entry_safe(frame, n, &ring->queue, list) {
		if (ring_full(ring))
			break;
		list_move_tail(&frame->list, &ring->in_flight);
		descriptor = &ring->descriptors[ring->head];
		descriptor->phys = frame->buffer_phy;
		descriptor->time = 0;
		descriptor->flags = flags;
		if (ring->is_tx) {
			descriptor->length = frame->size;
			descriptor->eof = frame->eof;
			descriptor->sof = frame->sof;
		}
		ring->head = (ring->head + 1) % ring->size;
		if (ring->is_tx)
			ring_iowrite_prod(ring, ring->head);
		else
			ring_iowrite_cons(ring, ring->head);
	}
}

/*
 * ring_work() - progress completed frames
 *
 * If the ring is shutting down then all frames are marked as canceled and
 * their callbacks are invoked.
 *
 * Otherwise we collect all completed frame from the ring buffer, write new
 * frame to the ring buffer and invoke the callbacks for the completed frames.
 */
static void ring_work(struct work_struct *work)
{
	struct tb_ring *ring = container_of(work, typeof(*ring), work);
	struct ring_frame *frame;
	bool canceled = false;
	unsigned long flags;
	LIST_HEAD(done);

	spin_lock_irqsave(&ring->lock, flags);

	if (!ring->running) {
		/*  Move all frames to done and mark them as canceled. */
		list_splice_tail_init(&ring->in_flight, &done);
		list_splice_tail_init(&ring->queue, &done);
		canceled = true;
		goto invoke_callback;
	}

	while (!ring_empty(ring)) {
		if (!(ring->descriptors[ring->tail].flags
				& RING_DESC_COMPLETED))
			break;
		frame = list_first_entry(&ring->in_flight, typeof(*frame),
					 list);
		list_move_tail(&frame->list, &done);
		if (!ring->is_tx) {
			frame->size = ring->descriptors[ring->tail].length;
			frame->eof = ring->descriptors[ring->tail].eof;
			frame->sof = ring->descriptors[ring->tail].sof;
			frame->flags = ring->descriptors[ring->tail].flags;
		}
		ring->tail = (ring->tail + 1) % ring->size;
	}
	ring_write_descriptors(ring);

invoke_callback:
	/* allow callbacks to schedule new work */
	spin_unlock_irqrestore(&ring->lock, flags);
	while (!list_empty(&done)) {
		frame = list_first_entry(&done, typeof(*frame), list);
		/*
		 * The callback may reenqueue or delete frame.
		 * Do not hold on to it.
		 */
		list_del_init(&frame->list);
		if (frame->callback)
			frame->callback(ring, frame, canceled);
	}

	wake_up(&ring->wait);
}

int __tb_ring_enqueue(struct tb_ring *ring, struct ring_frame *frame)
{
	unsigned long flags;
	int ret = 0;

	spin_lock_irqsave(&ring->lock, flags);
	if (ring->running) {
		list_add_tail(&frame->list, &ring->queue);
		ring_write_descriptors(ring);
	} else {
		ret = -ESHUTDOWN;
	}
	spin_unlock_irqrestore(&ring->lock, flags);
	return ret;
}
EXPORT_SYMBOL_GPL(__tb_ring_enqueue);

/**
 * tb_ring_poll() - Poll one completed frame from the ring
 * @ring: Ring to poll
 *
 * This function can be called when @start_poll callback of the @ring
 * has been called or the ring is created with %RING_FLAG_NO_INTERRUPT.
 * It will read one completed frame from the ring and return it to the
 * caller.
 *
 * Return: Pointer to &struct ring_frame, %NULL if there is no more
 * completed frames.
 */
struct ring_frame *tb_ring_poll(struct tb_ring *ring)
{
	struct ring_frame *frame = NULL;
	unsigned long flags;

	spin_lock_irqsave(&ring->lock, flags);
	if (!ring->running)
		goto unlock;
	if (ring_empty(ring))
		goto unlock;

	if (ring->descriptors[ring->tail].flags & RING_DESC_COMPLETED) {
		frame = list_first_entry(&ring->in_flight, typeof(*frame),
					 list);
		list_del_init(&frame->list);

		if (!ring->is_tx) {
			frame->size = ring->descriptors[ring->tail].length;
			frame->eof = ring->descriptors[ring->tail].eof;
			frame->sof = ring->descriptors[ring->tail].sof;
			frame->flags = ring->descriptors[ring->tail].flags;
		}

		ring->tail = (ring->tail + 1) % ring->size;
	}

unlock:
	spin_unlock_irqrestore(&ring->lock, flags);
	return frame;
}
EXPORT_SYMBOL_GPL(tb_ring_poll);

static void __ring_interrupt_mask(struct tb_ring *ring, bool mask)
{
	int idx = ring_interrupt_index(ring);
	int reg = REG_RING_INTERRUPT_BASE + idx / 32 * 4;
	int bit = idx % 32;
	u32 val;

	val = ioread32(ring->nhi->iobase + reg);
	if (mask)
		val &= ~BIT(bit);
	else
		val |= BIT(bit);
	iowrite32(val, ring->nhi->iobase + reg);
}

/* Both @nhi->lock and @ring->lock should be held */
static void __ring_interrupt(struct tb_ring *ring)
{
	if (!ring->running)
		return;

	if (ring->start_poll) {
		__ring_interrupt_mask(ring, true);
		ring->start_poll(ring->poll_data);
	} else {
		schedule_work(&ring->work);
	}
}

/**
 * tb_ring_poll_complete() - Re-start interrupt for the ring
 * @ring: Ring to re-start the interrupt
 *
 * This will re-start (unmask) the ring interrupt once the user is done
 * with polling.
 */
void tb_ring_poll_complete(struct tb_ring *ring)
{
	unsigned long flags;

	spin_lock_irqsave(&ring->nhi->lock, flags);
	spin_lock(&ring->lock);
	if (ring->start_poll)
		__ring_interrupt_mask(ring, false);
	spin_unlock(&ring->lock);
	spin_unlock_irqrestore(&ring->nhi->lock, flags);
}
EXPORT_SYMBOL_GPL(tb_ring_poll_complete);

static void ring_clear_msix(const struct tb_ring *ring)
{
	int bit;

	if (ring->nhi->quirks & QUIRK_AUTO_CLEAR_INT)
		return;

	bit = ring_interrupt_index(ring) & 31;
	if (ring->is_tx)
		iowrite32(BIT(bit), ring->nhi->iobase + REG_RING_INT_CLEAR);
	else
		iowrite32(BIT(bit), ring->nhi->iobase + REG_RING_INT_CLEAR +
			  4 * (ring->nhi->hop_count / 32));
}

irqreturn_t ring_msix(int irq, void *data)
{
	struct tb_ring *ring = data;

	spin_lock(&ring->nhi->lock);
	ring_clear_msix(ring);
	spin_lock(&ring->lock);
	__ring_interrupt(ring);
	spin_unlock(&ring->lock);
	spin_unlock(&ring->nhi->lock);

	return IRQ_HANDLED;
}

static int nhi_alloc_hop(struct tb_nhi *nhi, struct tb_ring *ring)
{
	unsigned int start_hop = RING_FIRST_USABLE_HOPID;
	int ret = 0;

	if (nhi->quirks & QUIRK_E2E) {
		start_hop = RING_FIRST_USABLE_HOPID + 1;
		if (ring->flags & RING_FLAG_E2E && !ring->is_tx) {
			dev_dbg(nhi->dev, "quirking E2E TX HopID %u -> %u\n",
				ring->e2e_tx_hop, RING_E2E_RESERVED_HOPID);
			ring->e2e_tx_hop = RING_E2E_RESERVED_HOPID;
		}
	}

	spin_lock_irq(&nhi->lock);

	if (ring->hop < 0) {
		unsigned int i;

		/*
		 * Automatically allocate HopID from the non-reserved
		 * range 1 .. hop_count - 1.
		 */
		for (i = start_hop; i < nhi->hop_count; i++) {
			if (ring->is_tx) {
				if (!nhi->tx_rings[i]) {
					ring->hop = i;
					break;
				}
			} else {
				if (!nhi->rx_rings[i]) {
					ring->hop = i;
					break;
				}
			}
		}
	}

	if (ring->hop > 0 && ring->hop < start_hop) {
		dev_warn(nhi->dev, "invalid hop: %d\n", ring->hop);
		ret = -EINVAL;
		goto err_unlock;
	}
	if (ring->hop < 0 || ring->hop >= nhi->hop_count) {
		dev_warn(nhi->dev, "invalid hop: %d\n", ring->hop);
		ret = -EINVAL;
		goto err_unlock;
	}
	if (ring->is_tx && nhi->tx_rings[ring->hop]) {
		dev_warn(nhi->dev, "TX hop %d already allocated\n",
			 ring->hop);
		ret = -EBUSY;
		goto err_unlock;
	}
	if (!ring->is_tx && nhi->rx_rings[ring->hop]) {
		dev_warn(nhi->dev, "RX hop %d already allocated\n",
			 ring->hop);
		ret = -EBUSY;
		goto err_unlock;
	}

	if (ring->is_tx)
		nhi->tx_rings[ring->hop] = ring;
	else
		nhi->rx_rings[ring->hop] = ring;

err_unlock:
	spin_unlock_irq(&nhi->lock);

	return ret;
}

static struct tb_ring *tb_ring_alloc(struct tb_nhi *nhi, u32 hop, int size,
				     bool transmit, unsigned int flags,
				     int e2e_tx_hop, u16 sof_mask, u16 eof_mask,
				     void (*start_poll)(void *),
				     void *poll_data)
{
	struct tb_ring *ring = NULL;

	dev_dbg(nhi->dev, "allocating %s ring %d of size %d\n",
		transmit ? "TX" : "RX", hop, size);

	if ((flags & RING_FLAG_NO_INTERRUPT) && start_poll) {
		dev_WARN(nhi->dev,
			 "start_poll() and NO_INTERRUPT cannot be used at the same time\n");
		return NULL;
	}

	ring = kzalloc_obj(*ring);
	if (!ring)
		return NULL;

	spin_lock_init(&ring->lock);
	INIT_LIST_HEAD(&ring->queue);
	INIT_LIST_HEAD(&ring->in_flight);
	INIT_WORK(&ring->work, ring_work);
	init_waitqueue_head(&ring->wait);

	ring->nhi = nhi;
	ring->hop = hop;
	ring->is_tx = transmit;
	ring->size = size;
	ring->flags = flags;
	ring->e2e_tx_hop = e2e_tx_hop;
	ring->sof_mask = sof_mask;
	ring->eof_mask = eof_mask;
	ring->head = 0;
	ring->tail = 0;
	ring->running = false;
	ring->start_poll = start_poll;
	ring->poll_data = poll_data;

	ring->descriptors = dma_alloc_coherent(ring->nhi->dev,
					       size * sizeof(*ring->descriptors),
					       &ring->descriptors_dma, GFP_KERNEL | __GFP_ZERO);
	if (!ring->descriptors)
		goto err_free_ring;

	if (!(flags & RING_FLAG_NO_INTERRUPT) && nhi->ops->request_ring_irq) {
		if (nhi->ops->request_ring_irq(ring, flags & RING_FLAG_NO_SUSPEND))
			goto err_free_descs;
	}

	if (nhi_alloc_hop(nhi, ring))
		goto err_release_msix;

	return ring;

err_release_msix:
	if (nhi->ops->release_ring_irq)
		nhi->ops->release_ring_irq(ring);
err_free_descs:
	dma_free_coherent(ring->nhi->dev,
			  ring->size * sizeof(*ring->descriptors),
			  ring->descriptors, ring->descriptors_dma);
err_free_ring:
	kfree(ring);

	return NULL;
}

/**
 * tb_ring_alloc_tx() - Allocate DMA ring for transmit
 * @nhi: Pointer to the NHI the ring is to be allocated
 * @hop: HopID (ring) to allocate
 * @size: Number of entries in the ring
 * @flags: Flags for the ring
 *
 * Return: Pointer to &struct tb_ring, %NULL otherwise.
 */
struct tb_ring *tb_ring_alloc_tx(struct tb_nhi *nhi, int hop, int size,
				 unsigned int flags)
{
	return tb_ring_alloc(nhi, hop, size, true, flags, 0, 0, 0, NULL, NULL);
}
EXPORT_SYMBOL_GPL(tb_ring_alloc_tx);

/**
 * tb_ring_alloc_rx() - Allocate DMA ring for receive
 * @nhi: Pointer to the NHI the ring is to be allocated
 * @hop: HopID (ring) to allocate. Pass %-1 for automatic allocation.
 * @size: Number of entries in the ring
 * @flags: Flags for the ring
 * @e2e_tx_hop: Transmit HopID when E2E is enabled in @flags
 * @sof_mask: Mask of PDF values that start a frame
 * @eof_mask: Mask of PDF values that end a frame
 * @start_poll: If not %NULL the ring will call this function when an
 *		interrupt is triggered and masked, instead of callback
 *		in each Rx frame.
 * @poll_data: Optional data passed to @start_poll
 *
 * Return: Pointer to &struct tb_ring, %NULL otherwise.
 */
struct tb_ring *tb_ring_alloc_rx(struct tb_nhi *nhi, int hop, int size,
				 unsigned int flags, int e2e_tx_hop,
				 u16 sof_mask, u16 eof_mask,
				 void (*start_poll)(void *), void *poll_data)
{
	return tb_ring_alloc(nhi, hop, size, false, flags, e2e_tx_hop, sof_mask, eof_mask,
			     start_poll, poll_data);
}
EXPORT_SYMBOL_GPL(tb_ring_alloc_rx);

/**
 * tb_ring_start() - enable a ring
 * @ring: Ring to start
 *
 * Must not be invoked in parallel with tb_ring_stop().
 */
void tb_ring_start(struct tb_ring *ring)
{
	u16 frame_size;
	u32 flags;

	spin_lock_irq(&ring->nhi->lock);
	spin_lock(&ring->lock);
	if (ring->nhi->going_away)
		goto err;
	if (ring->running) {
		dev_WARN(ring->nhi->dev, "ring already started\n");
		goto err;
	}
	dev_dbg(ring->nhi->dev, "starting %s %d\n",
		RING_TYPE(ring), ring->hop);

	if (ring->flags & RING_FLAG_FRAME) {
		/* Means 4096 */
		frame_size = 0;
		flags = RING_FLAG_ENABLE;
	} else {
		frame_size = TB_FRAME_SIZE;
		flags = RING_FLAG_ENABLE | RING_FLAG_RAW;
	}

	ring_iowrite64desc(ring, ring->descriptors_dma, 0);
	if (ring->is_tx) {
		ring_iowrite32desc(ring, ring->size, 12);
		ring_iowrite32options(ring, 0, 4);
		ring_iowrite32options(ring, flags, 0);
	} else {
		u32 sof_eof_mask = ring->sof_mask << 16 | ring->eof_mask;

		ring_iowrite32desc(ring, (frame_size << 16) | ring->size, 12);
		ring_iowrite32options(ring, sof_eof_mask, 4);
		ring_iowrite32options(ring, flags, 0);
	}

	/*
	 * Now that the ring valid bit is set we can configure E2E if
	 * enabled for the ring.
	 */
	if (ring->flags & RING_FLAG_E2E) {
		if (!ring->is_tx) {
			u32 hop;

			hop = ring->e2e_tx_hop << REG_RX_OPTIONS_E2E_HOP_SHIFT;
			hop &= REG_RX_OPTIONS_E2E_HOP_MASK;
			flags |= hop;

			dev_dbg(ring->nhi->dev,
				"enabling E2E for %s %d with TX HopID %d\n",
				RING_TYPE(ring), ring->hop, ring->e2e_tx_hop);
		} else {
			dev_dbg(ring->nhi->dev, "enabling E2E for %s %d\n",
				RING_TYPE(ring), ring->hop);
		}

		flags |= RING_FLAG_E2E_FLOW_CONTROL;
		ring_iowrite32options(ring, flags, 0);
	}

	if (!(ring->flags & RING_FLAG_NO_INTERRUPT))
		ring_interrupt_active(ring, true);
	ring->running = true;
err:
	spin_unlock(&ring->lock);
	spin_unlock_irq(&ring->nhi->lock);
}
EXPORT_SYMBOL_GPL(tb_ring_start);

static bool tb_ring_empty(struct tb_ring *ring)
{
	guard(spinlock_irqsave)(&ring->lock);
	return list_empty(&ring->in_flight);
}

/**
 * tb_ring_flush() - Waits for a ring to be empty
 * @ring: Ring to wait
 * @timeout_msec: Timeout in ms how long to wait.
 *
 * This can be called before stopping a ring to make sure all the frames
 * submitted prior have been completed.
 *
 * Return: %true if the ring is empty now, %false otherwise.
 */
bool tb_ring_flush(struct tb_ring *ring, unsigned int timeout_msec)
{
	if (!wait_event_timeout(ring->wait, tb_ring_empty(ring),
				msecs_to_jiffies(timeout_msec)))
		return false;
	return tb_ring_empty(ring);
}
EXPORT_SYMBOL_GPL(tb_ring_flush);

/**
 * tb_ring_stop() - shutdown a ring
 * @ring: Ring to stop
 *
 * Must not be invoked from a callback.
 *
 * This method will disable the ring. Further calls to
 * tb_ring_tx/tb_ring_rx will return -ESHUTDOWN until ring_stop has been
 * called.
 *
 * All enqueued frames will be canceled and their callbacks will be executed
 * with frame->canceled set to true (on the callback thread). This method
 * returns only after all callback invocations have finished.
 */
void tb_ring_stop(struct tb_ring *ring)
{
	spin_lock_irq(&ring->nhi->lock);
	spin_lock(&ring->lock);
	dev_dbg(ring->nhi->dev, "stopping %s %d\n",
		RING_TYPE(ring), ring->hop);
	if (ring->nhi->going_away)
		goto err;
	if (!ring->running) {
		dev_WARN(ring->nhi->dev, "%s %d already stopped\n",
			 RING_TYPE(ring), ring->hop);
		goto err;
	}
	if (!(ring->flags & RING_FLAG_NO_INTERRUPT))
		ring_interrupt_active(ring, false);

	ring_iowrite32options(ring, 0, 0);
	ring_iowrite64desc(ring, 0, 0);
	ring_iowrite32desc(ring, 0, 8);
	ring_iowrite32desc(ring, 0, 12);
	ring->head = 0;
	ring->tail = 0;
	ring->running = false;

err:
	spin_unlock(&ring->lock);
	spin_unlock_irq(&ring->nhi->lock);

	/*
	 * schedule ring->work to invoke callbacks on all remaining frames.
	 */
	schedule_work(&ring->work);
	flush_work(&ring->work);
}
EXPORT_SYMBOL_GPL(tb_ring_stop);

/*
 * tb_ring_free() - free ring
 *
 * When this method returns all invocations of ring->callback will have
 * finished.
 *
 * Ring must be stopped.
 *
 * Must NOT be called from ring_frame->callback!
 */
void tb_ring_free(struct tb_ring *ring)
{
	struct tb_nhi *nhi = ring->nhi;

	spin_lock_irq(&ring->nhi->lock);
	/*
	 * Dissociate the ring from the NHI. This also ensures that
	 * nhi_interrupt_work cannot reschedule ring->work.
	 */
	if (ring->is_tx)
		ring->nhi->tx_rings[ring->hop] = NULL;
	else
		ring->nhi->rx_rings[ring->hop] = NULL;

	if (ring->running) {
		dev_WARN(ring->nhi->dev, "%s %d still running\n",
			 RING_TYPE(ring), ring->hop);
	}
	spin_unlock_irq(&ring->nhi->lock);

	if (nhi->ops->release_ring_irq)
		nhi->ops->release_ring_irq(ring);

	dma_free_coherent(ring->nhi->dev,
			  ring->size * sizeof(*ring->descriptors),
			  ring->descriptors, ring->descriptors_dma);

	ring->descriptors = NULL;
	ring->descriptors_dma = 0;


	dev_dbg(ring->nhi->dev, "freeing %s %d\n", RING_TYPE(ring),
		ring->hop);

	/*
	 * ring->work can no longer be scheduled (it is scheduled only
	 * by nhi_interrupt_work, ring_stop and ring_msix). Wait for it
	 * to finish before freeing the ring.
	 */
	flush_work(&ring->work);
	kfree(ring);
}
EXPORT_SYMBOL_GPL(tb_ring_free);

/**
 * tb_ring_throttling() - Configure throttling for ring interrupt
 * @ring: Ring to configure
 * @interval_nsec: Interval counter for moderation (in ns), %0 disables
 *
 * Enables or disables ring interrupt throttling. The ring must be
 * stopped for this to be called. Granularity is 256 ns.
 *
 * Return: %0 on success, negative errno otherwise.
 */
int tb_ring_throttling(struct tb_ring *ring, unsigned int interval_nsec)
{
	guard(spinlock_irqsave)(&ring->lock);
	if (WARN_ON_ONCE(ring->running))
		return -EBUSY;
	ring->interval_nsec = interval_nsec;
	return 0;
}
EXPORT_SYMBOL_GPL(tb_ring_throttling);

/**
 * nhi_mailbox_cmd() - Send a command through NHI mailbox
 * @nhi: Pointer to the NHI structure
 * @cmd: Command to send
 * @data: Data to be send with the command
 *
 * Sends mailbox command to the firmware running on NHI.
 *
 * Return: %0 on success, negative errno otherwise.
 */
int nhi_mailbox_cmd(struct tb_nhi *nhi, enum nhi_mailbox_cmd cmd, u32 data)
{
	ktime_t timeout;
	u32 val;

	iowrite32(data, nhi->iobase + REG_INMAIL_DATA);

	val = ioread32(nhi->iobase + REG_INMAIL_CMD);
	val &= ~(REG_INMAIL_CMD_MASK | REG_INMAIL_ERROR);
	val |= REG_INMAIL_OP_REQUEST | cmd;
	iowrite32(val, nhi->iobase + REG_INMAIL_CMD);

	timeout = ktime_add_ms(ktime_get(), NHI_MAILBOX_TIMEOUT);
	do {
		val = ioread32(nhi->iobase + REG_INMAIL_CMD);
		if (!(val & REG_INMAIL_OP_REQUEST))
			break;
		usleep_range(10, 20);
	} while (ktime_before(ktime_get(), timeout));

	if (val & REG_INMAIL_OP_REQUEST)
		return -ETIMEDOUT;
	if (val & REG_INMAIL_ERROR)
		return -EIO;

	return 0;
}

/**
 * nhi_mailbox_mode() - Return current firmware operation mode
 * @nhi: Pointer to the NHI structure
 *
 * The function reads current firmware operation mode using NHI mailbox
 * registers and returns it to the caller.
 *
 * Return: &enum nhi_fw_mode.
 */
enum nhi_fw_mode nhi_mailbox_mode(struct tb_nhi *nhi)
{
	u32 val;

	val = ioread32(nhi->iobase + REG_OUTMAIL_CMD);
	val &= REG_OUTMAIL_CMD_OPMODE_MASK;
	val >>= REG_OUTMAIL_CMD_OPMODE_SHIFT;

	return (enum nhi_fw_mode)val;
}

void nhi_interrupt_work(struct work_struct *work)
{
	struct tb_nhi *nhi = container_of(work, typeof(*nhi), interrupt_work);
	int value = 0; /* Suppress uninitialized usage warning. */
	int bit;
	int hop = -1;
	int type = 0; /* current interrupt type 0: TX, 1: RX, 2: RX overflow */
	struct tb_ring *ring;

	spin_lock_irq(&nhi->lock);

	/*
	 * Starting at REG_RING_NOTIFY_BASE there are three status bitfields
	 * (TX, RX, RX overflow). We iterate over the bits and read a new
	 * dwords as required. The registers are cleared on read.
	 */
	for (bit = 0; bit < 3 * nhi->hop_count; bit++) {
		if (bit % 32 == 0)
			value = ioread32(nhi->iobase
					 + REG_RING_NOTIFY_BASE
					 + 4 * (bit / 32));
		if (++hop == nhi->hop_count) {
			hop = 0;
			type++;
		}
		if ((value & (1 << (bit % 32))) == 0)
			continue;
		if (type == 2) {
			dev_warn(nhi->dev, "RX overflow for ring %d\n", hop);
			continue;
		}
		if (type == 0)
			ring = nhi->tx_rings[hop];
		else
			ring = nhi->rx_rings[hop];
		if (ring == NULL) {
			dev_warn(nhi->dev,
				 "got interrupt for inactive %s ring %d\n",
				 type ? "RX" : "TX",
				 hop);
			continue;
		}

		spin_lock(&ring->lock);
		__ring_interrupt(ring);
		spin_unlock(&ring->lock);
	}
	spin_unlock_irq(&nhi->lock);
}

irqreturn_t nhi_msi(int irq, void *data)
{
	struct tb_nhi *nhi = data;
	schedule_work(&nhi->interrupt_work);
	return IRQ_HANDLED;
}

static int __nhi_suspend_noirq(struct device *dev, bool wakeup)
{
	struct tb *tb = dev_get_drvdata(dev);
	struct tb_nhi *nhi = tb->nhi;
	int ret;

	ret = tb_domain_suspend_noirq(tb);
	if (ret)
		return ret;

	if (nhi->ops->suspend_noirq) {
		ret = nhi->ops->suspend_noirq(tb->nhi, wakeup);
		if (ret)
			return ret;
	}

	return 0;
}

static int nhi_suspend_noirq(struct device *dev)
{
	return __nhi_suspend_noirq(dev, device_may_wakeup(dev));
}

static int nhi_freeze_noirq(struct device *dev)
{
	struct tb *tb = dev_get_drvdata(dev);

	return tb_domain_freeze_noirq(tb);
}

static int nhi_thaw_noirq(struct device *dev)
{
	struct tb *tb = dev_get_drvdata(dev);

	return tb_domain_thaw_noirq(tb);
}

static bool nhi_wake_supported(struct device *dev)
{
	u8 val;

	/*
	 * If power rails are sustainable for wakeup from S4 this
	 * property is set by the BIOS.
	 */
	if (!device_property_read_u8(dev, "WAKE_SUPPORTED", &val))
		return !!val;

	return true;
}

static int nhi_poweroff_noirq(struct device *dev)
{
	bool wakeup;

	wakeup = device_may_wakeup(dev) && nhi_wake_supported(dev);
	return __nhi_suspend_noirq(dev, wakeup);
}

static int nhi_resume_noirq(struct device *dev)
{
	struct tb *tb = dev_get_drvdata(dev);
	struct tb_nhi *nhi = tb->nhi;
	int ret;

	/*
	 * Check that the device is still there. It may be that the user
	 * unplugged last device which causes the host controller to go
	 * away on PCs.
	 */
	if ((nhi->ops->is_present && !nhi->ops->is_present(nhi))) {
		nhi->going_away = true;
	} else if (nhi->ops->resume_noirq) {
		ret = nhi->ops->resume_noirq(nhi);
		if (ret)
			return ret;
	}

	return tb_domain_resume_noirq(tb);
}

static int nhi_suspend(struct device *dev)
{
	struct tb *tb = dev_get_drvdata(dev);

	return tb_domain_suspend(tb);
}

static void nhi_complete(struct device *dev)
{
	struct tb *tb = dev_get_drvdata(dev);

	/*
	 * If we were runtime suspended when system suspend started,
	 * schedule runtime resume now. It should bring the domain back
	 * to functional state.
	 */
	if (pm_runtime_suspended(dev))
		pm_runtime_resume(dev);
	else
		tb_domain_complete(tb);
}

static int nhi_runtime_suspend(struct device *dev)
{
	struct tb *tb = dev_get_drvdata(dev);
	struct tb_nhi *nhi = tb->nhi;
	int ret;

	ret = tb_domain_runtime_suspend(tb);
	if (ret)
		return ret;

	if (nhi->ops->runtime_suspend) {
		ret = nhi->ops->runtime_suspend(tb->nhi);
		if (ret)
			return ret;
	}
	return 0;
}

static int nhi_runtime_resume(struct device *dev)
{
	struct tb *tb = dev_get_drvdata(dev);
	struct tb_nhi *nhi = tb->nhi;
	int ret;

	if (nhi->ops->runtime_resume) {
		ret = nhi->ops->runtime_resume(nhi);
		if (ret)
			return ret;
	}

	return tb_domain_runtime_resume(tb);
}

void nhi_shutdown(struct tb_nhi *nhi)
{
	int i;

	dev_dbg(nhi->dev, "shutdown\n");

	for (i = 0; i < nhi->hop_count; i++) {
		if (nhi->tx_rings[i])
			dev_WARN(nhi->dev,
				 "TX ring %d is still active\n", i);
		if (nhi->rx_rings[i])
			dev_WARN(nhi->dev,
				 "RX ring %d is still active\n", i);
	}
	nhi_disable_interrupts(nhi);

	if (nhi->ops->shutdown)
		nhi->ops->shutdown(nhi);
}

static void nhi_reset(struct tb_nhi *nhi)
{
	ktime_t timeout;
	u32 val;

	val = ioread32(nhi->iobase + REG_CAPS);
	/* Reset only v2 and later routers */
	if (FIELD_GET(REG_CAPS_VERSION_MASK, val) < REG_CAPS_VERSION_2)
		return;

	if (!host_reset) {
		dev_dbg(nhi->dev, "skipping host router reset\n");
		return;
	}

	iowrite32(REG_RESET_HRR, nhi->iobase + REG_RESET);
	msleep(100);

	timeout = ktime_add_ms(ktime_get(), 500);
	do {
		val = ioread32(nhi->iobase + REG_RESET);
		if (!(val & REG_RESET_HRR)) {
			dev_warn(nhi->dev, "host router reset successful\n");
			return;
		}
		usleep_range(10, 20);
	} while (ktime_before(ktime_get(), timeout));

	dev_warn(nhi->dev, "timeout resetting host router\n");
}

/**
 * nhi_reset_interface() - Reset the host interface
 * @nhi: Host interface to reset
 *
 * Brings the registers in the memory BAR back to their default state and
 * clears the End-to-End Flow Control state. The caller is responsible for
 * stopping the control channel over the reset because it clears the ring
 * state as well.
 */
void nhi_reset_interface(struct tb_nhi *nhi)
{
	u32 val;

	val = ioread32(nhi->iobase + REG_CAPS);
	/* Only v1 host interfaces implement the reset */
	if (FIELD_GET(REG_CAPS_VERSION_MASK, val) >= REG_CAPS_VERSION_2)
		return;

	dev_dbg(nhi->dev, "issuing host interface reset\n");

	iowrite32(REG_HOST_INTERFACE_RESET_RST,
		  nhi->iobase + REG_HOST_INTERFACE_RESET);
	/* Wait for tHIReset (10 ms) to complete */
	usleep_range(10000, 20000);
}

static struct tb *nhi_select_cm(struct tb_nhi *nhi)
{
	struct tb *tb;

	/*
	 * USB4 case is simple. If we got control of any of the
	 * capabilities, we use software CM.
	 */
	if (tb_acpi_is_native())
		return tb_probe(nhi);

	/*
	 * Either firmware based CM is running (we did not get control
	 * from the firmware) or this is pre-USB4 PC so try first
	 * firmware CM and then fallback to software CM.
	 */
	tb = icm_probe(nhi);
	if (!tb)
		tb = tb_probe(nhi);

	return tb;
}

int nhi_probe(struct tb_nhi *nhi)
{
	struct device *dev = nhi->dev;
	struct tb *tb;
	int res;

	if (!nhi->ops)
		return dev_err_probe(dev, -EINVAL, "NHI ops not set\n");

	if (!nhi->ops->init_interrupts)
		return dev_err_probe(dev, -EINVAL, "missing required NHI ops\n");

	nhi->hop_count = ioread32(nhi->iobase + REG_CAPS) & 0x3ff;
	dev_dbg(dev, "total paths: %d\n", nhi->hop_count);

	nhi->tx_rings = devm_kcalloc(dev, nhi->hop_count,
				     sizeof(*nhi->tx_rings), GFP_KERNEL);
	nhi->rx_rings = devm_kcalloc(dev, nhi->hop_count,
				     sizeof(*nhi->rx_rings), GFP_KERNEL);
	if (!nhi->tx_rings || !nhi->rx_rings)
		return -ENOMEM;

	nhi_reset(nhi);

	/* In case someone left them on. */
	nhi_disable_interrupts(nhi);

	res = nhi->ops->init_interrupts(nhi);
	if (res)
		return dev_err_probe(dev, res, "cannot enable interrupts, aborting\n");

	spin_lock_init(&nhi->lock);

	res = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64));
	if (res)
		return dev_err_probe(dev, res, "failed to set DMA mask\n");

	if (nhi->ops->init) {
		res = nhi->ops->init(nhi);
		if (res)
			return dev_err_probe(dev, res, "NHI specific init failed\n");
	}

	init_completion(&nhi->domain_released);

	tb = nhi_select_cm(nhi);
	if (!tb)
		return dev_err_probe(dev, -ENODEV,
			"failed to determine connection manager, aborting\n");

	dev_dbg(dev, "NHI initialized, starting thunderbolt\n");

	nhi->host_reset = host_reset;

	res = tb_domain_add(tb, host_reset);
	if (res) {
		/*
		 * At this point the RX/TX rings might already have been
		 * activated. Do a proper shutdown.
		 */
		tb_domain_put(tb);
		wait_for_completion(&nhi->domain_released);
		nhi_shutdown(nhi);
		return dev_err_probe(dev, res, "failed to add domain\n");
	}
	dev_set_drvdata(dev, tb);

	device_wakeup_enable(dev);

	pm_runtime_allow(dev);
	pm_runtime_set_autosuspend_delay(dev, TB_AUTOSUSPEND_DELAY);
	pm_runtime_use_autosuspend(dev);
	pm_runtime_put_autosuspend(dev);

	return 0;
}

/*
 * The tunneled pci bridges are siblings of us. Use resume_noirq to reenable
 * the tunnels asap. A corresponding pci quirk blocks the downstream bridges
 * resume_noirq until we are done.
 */
const struct dev_pm_ops nhi_pm_ops = {
	.suspend_noirq = nhi_suspend_noirq,
	.resume_noirq = nhi_resume_noirq,
	.freeze_noirq = nhi_freeze_noirq,  /*
					    * we just disable hotplug, the
					    * pci-tunnels stay alive.
					    */
	.thaw_noirq = nhi_thaw_noirq,
	.restore_noirq = nhi_resume_noirq,
	.suspend = nhi_suspend,
	.poweroff_noirq = nhi_poweroff_noirq,
	.poweroff = nhi_suspend,
	.complete = nhi_complete,
	.runtime_suspend = nhi_runtime_suspend,
	.runtime_resume = nhi_runtime_resume,
};