/*
 * Copyright (c) 2017 Ondrej Hlavaty
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <errno.h>
#include <assert.h>
#include <ddi.h>
#include <as.h>
#include <align.h>
#include <libarch/barrier.h>
#include <usb/debug.h>
#include "hw_struct/trb.h"
#include "trb_ring.h"

#define SEGMENT_HEADER_SIZE (sizeof(link_t) + sizeof(uintptr_t))

/**
 * Number of TRBs in a segment (with our header).
 */
#define SEGMENT_TRB_COUNT ((PAGE_SIZE - SEGMENT_HEADER_SIZE) / sizeof(xhci_trb_t))

struct trb_segment {
	xhci_trb_t trb_storage [SEGMENT_TRB_COUNT];

	link_t segments_link;
	uintptr_t phys;
} __attribute__((aligned(PAGE_SIZE)));


/**
 * Get the first TRB of a segment.
 */
static inline xhci_trb_t *segment_begin(trb_segment_t *segment)
{
	return segment->trb_storage;
}

/**
 * Get the one-past-end TRB of a segment.
 */
static inline xhci_trb_t *segment_end(trb_segment_t *segment)
{
	return segment_begin(segment) + SEGMENT_TRB_COUNT;
}

/**
 * Allocate and initialize new segment.
 *
 * TODO: When the HC supports 64-bit addressing, there's no need to restrict
 * to DMAMEM_4GiB.
 */
static int trb_segment_alloc(trb_segment_t **segment)
{
	dma_buffer_t dbuf;

	const int err = dma_buffer_alloc(&dbuf, PAGE_SIZE);
	if (err)
		return err;

	*segment = dbuf.virt;
	memset(*segment, 0, PAGE_SIZE);
	(*segment)->phys = dbuf.phys;
	usb_log_debug2("Allocated new ring segment.");
	return EOK;
}

static void trb_segment_free(trb_segment_t *segment)
{
	dma_buffer_t dbuf = { .virt = segment, .phys = segment->phys };
	dma_buffer_free(&dbuf);
}

/**
 * Initializes the ring with one segment.
 */
int xhci_trb_ring_init(xhci_trb_ring_t *ring)
{
	struct trb_segment *segment;
	int err;

	list_initialize(&ring->segments);

	if ((err = trb_segment_alloc(&segment)) != EOK)
		return err;

	list_append(&segment->segments_link, &ring->segments);
	ring->segment_count = 1;

	xhci_trb_t *last = segment_end(segment) - 1;
	xhci_trb_link_fill(last, segment->phys);
	TRB_LINK_SET_TC(*last, true);

	ring->enqueue_segment = segment;
	ring->enqueue_trb = segment_begin(segment);
	ring->dequeue = segment->phys;
	ring->pcs = 1;

	fibril_mutex_initialize(&ring->guard);

	return EOK;
}

/**
 * Free all segments inside the ring.
 */
void xhci_trb_ring_fini(xhci_trb_ring_t *ring)
{
	assert(ring);

	list_foreach_safe(ring->segments, cur, next) {
		trb_segment_t *segment = list_get_instance(cur, trb_segment_t, segments_link);
		trb_segment_free(segment);
	}
}

/**
 * When the enqueue pointer targets a Link TRB, resolve it.
 *
 * Relies on segments being in the segment list in linked order.
 *
 * According to section 4.9.2.2, figure 16, the link TRBs cannot be chained, so
 * it shall not be called in cycle, nor have an inner cycle.
 */
static void trb_ring_resolve_link(xhci_trb_ring_t *ring)
{
	link_t *next_segment = list_next(&ring->enqueue_segment->segments_link, &ring->segments);
	if (!next_segment)
		next_segment = list_first(&ring->segments);

	ring->enqueue_segment = list_get_instance(next_segment, trb_segment_t, segments_link);
	ring->enqueue_trb = segment_begin(ring->enqueue_segment);
}

/**
 * Get the physical address of the enqueue pointer.
 */
static uintptr_t trb_ring_enqueue_phys(xhci_trb_ring_t *ring)
{
	uintptr_t trb_id = ring->enqueue_trb - segment_begin(ring->enqueue_segment);
	return ring->enqueue_segment->phys + trb_id * sizeof(xhci_trb_t);
}

/**
 * Decides whether the TRB will trigger an interrupt after being processed.
 */
static bool trb_generates_interrupt(xhci_trb_t *trb)
{
	return TRB_TYPE(*trb) >= XHCI_TRB_TYPE_ENABLE_SLOT_CMD
		|| TRB_IOC(*trb);
}

/**
 * Enqueue TD composed of TRBs.
 *
 * This will copy specified number of TRBs chained together into the ring. The
 * cycle flag in TRBs may be changed.
 *
 * The copied TRBs must be contiguous in memory, and must not contain Link TRBs.
 *
 * We cannot avoid the copying, because the TRB in ring should be updated atomically.
 *
 * @param first_trb the first TRB
 * @param trbs number of TRBS to enqueue
 * @param phys returns address of the last TRB enqueued
 * @return EOK on success,
 *         EAGAIN when the ring is too full to fit all TRBs (temporary)
 */
int xhci_trb_ring_enqueue_multiple(xhci_trb_ring_t *ring, xhci_trb_t *first_trb,
	size_t trbs, uintptr_t *phys)
{
	assert(trbs > 0);
	fibril_mutex_lock(&ring->guard);

	xhci_trb_t * const saved_enqueue_trb = ring->enqueue_trb;
	trb_segment_t * const saved_enqueue_segment = ring->enqueue_segment;
	if (phys)
		*phys = (uintptr_t)NULL;

	/*
	 * First, dry run and advance the enqueue pointer to see if the ring would
	 * be full anytime during the transaction.
	 */
	xhci_trb_t *trb = first_trb;
	for (size_t i = 0; i < trbs; ++i, ++trb) {
		if (trb_generates_interrupt(trb)) {
			if (*phys)
				return ENOTSUP;
			*phys = trb_ring_enqueue_phys(ring);
		}

		ring->enqueue_trb++;

		if (TRB_TYPE(*ring->enqueue_trb) == XHCI_TRB_TYPE_LINK)
			trb_ring_resolve_link(ring);

		if (trb_ring_enqueue_phys(ring) == ring->dequeue)
			goto err_again;
	}

	ring->enqueue_segment = saved_enqueue_segment;
	ring->enqueue_trb = saved_enqueue_trb;

	/*
	 * Now, copy the TRBs without further checking.
	 */
	trb = first_trb;
	for (size_t i = 0; i < trbs; ++i, ++trb) {
		TRB_SET_CYCLE(*trb, ring->pcs);
		xhci_trb_copy_to_pio(ring->enqueue_trb, trb);

		usb_log_debug2("TRB ring(%p): Enqueued TRB %p", ring, trb);
		ring->enqueue_trb++;

		if (TRB_TYPE(*ring->enqueue_trb) == XHCI_TRB_TYPE_LINK) {
			TRB_SET_CYCLE(*ring->enqueue_trb, ring->pcs);

			if (TRB_LINK_TC(*ring->enqueue_trb)) {
				ring->pcs = !ring->pcs;
				usb_log_debug2("TRB ring(%p): PCS toggled", ring);
			}

			trb_ring_resolve_link(ring);
		}
	}

	fibril_mutex_unlock(&ring->guard);
	return EOK;

err_again:
	ring->enqueue_segment = saved_enqueue_segment;
	ring->enqueue_trb = saved_enqueue_trb;
	fibril_mutex_unlock(&ring->guard);
	return EAGAIN;
}

/**
 * Enqueue TD composed of a single TRB. See: `xhci_trb_ring_enqueue_multiple`
 */
int xhci_trb_ring_enqueue(xhci_trb_ring_t *ring, xhci_trb_t *td, uintptr_t *phys)
{
	return xhci_trb_ring_enqueue_multiple(ring, td, 1, phys);
}

/**
 * Initializes an event ring.
 */
int xhci_event_ring_init(xhci_event_ring_t *ring)
{
	struct trb_segment *segment;
	int err;

	list_initialize(&ring->segments);

	if ((err = trb_segment_alloc(&segment)) != EOK)
		return err;

	list_append(&segment->segments_link, &ring->segments);
	ring->segment_count = 1;

	ring->dequeue_segment = segment;
	ring->dequeue_trb = segment_begin(segment);
	ring->dequeue_ptr = segment->phys;

	if (dma_buffer_alloc(&ring->erst, PAGE_SIZE)) {
		xhci_event_ring_fini(ring);
		return ENOMEM;
	}
	xhci_erst_entry_t *erst = ring->erst.virt;

	memset(erst, 0, PAGE_SIZE);
	xhci_fill_erst_entry(&erst[0], segment->phys, SEGMENT_TRB_COUNT);

	ring->ccs = 1;

	fibril_mutex_initialize(&ring->guard);

	usb_log_debug("Initialized event ring.");

	return EOK;
}

void xhci_event_ring_fini(xhci_event_ring_t *ring)
{
	list_foreach_safe(ring->segments, cur, next) {
		trb_segment_t *segment = list_get_instance(cur, trb_segment_t, segments_link);
		dmamem_unmap_anonymous(segment);
	}

	dma_buffer_free(&ring->erst);
}

/**
 * Get the physical address of the dequeue pointer.
 */
static uintptr_t event_ring_dequeue_phys(xhci_event_ring_t *ring)
{
	uintptr_t trb_id = ring->dequeue_trb - segment_begin(ring->dequeue_segment);
	return ring->dequeue_segment->phys + trb_id * sizeof(xhci_trb_t);
}

/**
 * Fill the event with next valid event from the ring.
 *
 * @param event pointer to event to be overwritten
 * @return EOK on success,
 *         ENOENT when the ring is empty
 */
int xhci_event_ring_dequeue(xhci_event_ring_t *ring, xhci_trb_t *event)
{
	fibril_mutex_lock(&ring->guard);

	/**
	 * The ERDP reported to the HC is a half-phase off the one we need to
	 * maintain. Therefore, we keep it extra.
	 */
	ring->dequeue_ptr = event_ring_dequeue_phys(ring);

	if (TRB_CYCLE(*ring->dequeue_trb) != ring->ccs) {
		fibril_mutex_unlock(&ring->guard);
		return ENOENT; /* The ring is empty. */
	}

	/* Do not reorder the Cycle bit reading with memcpy */
	read_barrier();

	memcpy(event, ring->dequeue_trb, sizeof(xhci_trb_t));

	ring->dequeue_trb++;
	const unsigned index = ring->dequeue_trb - segment_begin(ring->dequeue_segment);

	/* Wrapping around segment boundary */
	if (index >= SEGMENT_TRB_COUNT) {
		link_t *next_segment = list_next(&ring->dequeue_segment->segments_link, &ring->segments);

		/* Wrapping around table boundary */
		if (!next_segment) {
			next_segment = list_first(&ring->segments);
			ring->ccs = !ring->ccs;
		}

		ring->dequeue_segment = list_get_instance(next_segment, trb_segment_t, segments_link);
		ring->dequeue_trb = segment_begin(ring->dequeue_segment);
	}

	fibril_mutex_unlock(&ring->guard);
	return EOK;
}