// SPDX-License-Identifier: (GPL-2.0 OR MIT)
/* Google virtual Ethernet (gve) driver
 *
 * Copyright (C) 2015-2024 Google, Inc.
 */

#include "gve.h"
#include "gve_utils.h"

int gve_buf_ref_cnt(struct gve_rx_buf_state_dqo *bs)
{
	return page_count(bs->page_info.page) - bs->page_info.pagecnt_bias;
}

struct gve_rx_buf_state_dqo *gve_alloc_buf_state(struct gve_rx_ring *rx)
{
	struct gve_rx_buf_state_dqo *buf_state;
	s16 buffer_id;

	buffer_id = rx->dqo.free_buf_states;
	if (unlikely(buffer_id == -1))
		return NULL;

	buf_state = &rx->dqo.buf_states[buffer_id];

	/* Remove buf_state from free list */
	rx->dqo.free_buf_states = buf_state->next;

	/* Point buf_state to itself to mark it as allocated */
	buf_state->next = buffer_id;

	return buf_state;
}

bool gve_buf_state_is_allocated(struct gve_rx_ring *rx,
				struct gve_rx_buf_state_dqo *buf_state)
{
	s16 buffer_id = buf_state - rx->dqo.buf_states;

	return buf_state->next == buffer_id;
}

void gve_free_buf_state(struct gve_rx_ring *rx,
			struct gve_rx_buf_state_dqo *buf_state)
{
	s16 buffer_id = buf_state - rx->dqo.buf_states;

	buf_state->next = rx->dqo.free_buf_states;
	rx->dqo.free_buf_states = buffer_id;
}

struct gve_rx_buf_state_dqo *gve_dequeue_buf_state(struct gve_rx_ring *rx,
						   struct gve_index_list *list)
{
	struct gve_rx_buf_state_dqo *buf_state;
	s16 buffer_id;

	buffer_id = list->head;
	if (unlikely(buffer_id == -1))
		return NULL;

	buf_state = &rx->dqo.buf_states[buffer_id];

	/* Remove buf_state from list */
	list->head = buf_state->next;
	if (buf_state->next == -1)
		list->tail = -1;

	/* Point buf_state to itself to mark it as allocated */
	buf_state->next = buffer_id;

	return buf_state;
}

void gve_enqueue_buf_state(struct gve_rx_ring *rx, struct gve_index_list *list,
			   struct gve_rx_buf_state_dqo *buf_state)
{
	s16 buffer_id = buf_state - rx->dqo.buf_states;

	buf_state->next = -1;

	if (list->head == -1) {
		list->head = buffer_id;
		list->tail = buffer_id;
	} else {
		int tail = list->tail;

		rx->dqo.buf_states[tail].next = buffer_id;
		list->tail = buffer_id;
	}
}

struct gve_rx_buf_state_dqo *gve_get_recycled_buf_state(struct gve_rx_ring *rx)
{
	struct gve_rx_buf_state_dqo *buf_state;
	int i;

	/* Recycled buf states are immediately usable. */
	buf_state = gve_dequeue_buf_state(rx, &rx->dqo.recycled_buf_states);
	if (likely(buf_state))
		return buf_state;

	if (unlikely(rx->dqo.used_buf_states.head == -1))
		return NULL;

	/* Used buf states are only usable when ref count reaches 0, which means
	 * no SKBs refer to them.
	 *
	 * Search a limited number before giving up.
	 */
	for (i = 0; i < 5; i++) {
		buf_state = gve_dequeue_buf_state(rx, &rx->dqo.used_buf_states);
		if (gve_buf_ref_cnt(buf_state) == 0) {
			rx->dqo.used_buf_states_cnt--;
			return buf_state;
		}

		gve_enqueue_buf_state(rx, &rx->dqo.used_buf_states, buf_state);
	}

	return NULL;
}

int gve_alloc_qpl_page_dqo(struct gve_rx_ring *rx,
			   struct gve_rx_buf_state_dqo *buf_state)
{
	struct gve_priv *priv = rx->gve;
	u32 idx;

	idx = rx->dqo.next_qpl_page_idx;
	if (idx >= gve_get_rx_pages_per_qpl_dqo(priv->rx_desc_cnt)) {
		net_err_ratelimited("%s: Out of QPL pages\n",
				    priv->dev->name);
		return -ENOMEM;
	}
	buf_state->page_info.page = rx->dqo.qpl->pages[idx];
	buf_state->addr = rx->dqo.qpl->page_buses[idx];
	rx->dqo.next_qpl_page_idx++;
	buf_state->page_info.page_offset = 0;
	buf_state->page_info.page_address =
		page_address(buf_state->page_info.page);
	buf_state->page_info.buf_size = priv->data_buffer_size_dqo;
	buf_state->last_single_ref_offset = 0;

	/* The page already has 1 ref. */
	page_ref_add(buf_state->page_info.page, INT_MAX - 1);
	buf_state->page_info.pagecnt_bias = INT_MAX;

	return 0;
}

void gve_free_qpl_page_dqo(struct gve_rx_buf_state_dqo *buf_state)
{
	if (!buf_state->page_info.page)
		return;

	page_ref_sub(buf_state->page_info.page,
		     buf_state->page_info.pagecnt_bias - 1);
	buf_state->page_info.page = NULL;
}

void gve_try_recycle_buf(struct gve_priv *priv, struct gve_rx_ring *rx,
			 struct gve_rx_buf_state_dqo *buf_state)
{
	const u16 data_buffer_size = priv->data_buffer_size_dqo;
	int pagecount;

	/* Can't reuse if we only fit one buffer per page */
	if (data_buffer_size * 2 > PAGE_SIZE)
		goto mark_used;

	pagecount = gve_buf_ref_cnt(buf_state);

	/* Record the offset when we have a single remaining reference.
	 *
	 * When this happens, we know all of the other offsets of the page are
	 * usable.
	 */
	if (pagecount == 1) {
		buf_state->last_single_ref_offset =
			buf_state->page_info.page_offset;
	}

	/* Use the next buffer sized chunk in the page. */
	buf_state->page_info.page_offset += data_buffer_size;
	buf_state->page_info.page_offset &= (PAGE_SIZE - 1);

	/* If we wrap around to the same offset without ever dropping to 1
	 * reference, then we don't know if this offset was ever freed.
	 */
	if (buf_state->page_info.page_offset ==
	    buf_state->last_single_ref_offset) {
		goto mark_used;
	}

	gve_enqueue_buf_state(rx, &rx->dqo.recycled_buf_states, buf_state);
	return;

mark_used:
	gve_enqueue_buf_state(rx, &rx->dqo.used_buf_states, buf_state);
	rx->dqo.used_buf_states_cnt++;
}

void gve_free_to_page_pool(struct gve_rx_ring *rx,
			   struct gve_rx_buf_state_dqo *buf_state,
			   bool allow_direct)
{
	struct page *page = buf_state->page_info.page;

	if (!page)
		return;

	page_pool_put_full_page(page->pp, page, allow_direct);
	buf_state->page_info.page = NULL;
}

static int gve_alloc_from_page_pool(struct gve_rx_ring *rx,
				    struct gve_rx_buf_state_dqo *buf_state)
{
	struct gve_priv *priv = rx->gve;
	struct page *page;

	buf_state->page_info.buf_size = priv->data_buffer_size_dqo;
	page = page_pool_alloc(rx->dqo.page_pool,
			       &buf_state->page_info.page_offset,
			       &buf_state->page_info.buf_size, GFP_ATOMIC);

	if (!page)
		return -ENOMEM;

	buf_state->page_info.page = page;
	buf_state->page_info.page_address = page_address(page);
	buf_state->addr = page_pool_get_dma_addr(page);

	return 0;
}

struct page_pool *gve_rx_create_page_pool(struct gve_priv *priv,
					  struct gve_rx_ring *rx)
{
	u32 ntfy_id = gve_rx_idx_to_ntfy(priv, rx->q_num);
	struct page_pool_params pp = {
		.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV,
		.order = 0,
		.pool_size = GVE_PAGE_POOL_SIZE_MULTIPLIER * priv->rx_desc_cnt,
		.dev = &priv->pdev->dev,
		.netdev = priv->dev,
		.napi = &priv->ntfy_blocks[ntfy_id].napi,
		.max_len = PAGE_SIZE,
		.dma_dir = DMA_FROM_DEVICE,
	};

	return page_pool_create(&pp);
}

void gve_free_buffer(struct gve_rx_ring *rx,
		     struct gve_rx_buf_state_dqo *buf_state)
{
	if (rx->dqo.page_pool) {
		gve_free_to_page_pool(rx, buf_state, true);
		gve_free_buf_state(rx, buf_state);
	} else {
		gve_enqueue_buf_state(rx, &rx->dqo.recycled_buf_states,
				      buf_state);
	}
}

void gve_reuse_buffer(struct gve_rx_ring *rx,
		      struct gve_rx_buf_state_dqo *buf_state)
{
	if (rx->dqo.page_pool) {
		buf_state->page_info.page = NULL;
		gve_free_buf_state(rx, buf_state);
	} else {
		gve_dec_pagecnt_bias(&buf_state->page_info);
		gve_try_recycle_buf(rx->gve, rx, buf_state);
	}
}

int gve_alloc_buffer(struct gve_rx_ring *rx, struct gve_rx_desc_dqo *desc)
{
	struct gve_rx_buf_state_dqo *buf_state;

	if (rx->dqo.page_pool) {
		buf_state = gve_alloc_buf_state(rx);
		if (WARN_ON_ONCE(!buf_state))
			return -ENOMEM;

		if (gve_alloc_from_page_pool(rx, buf_state))
			goto free_buf_state;
	} else {
		buf_state = gve_get_recycled_buf_state(rx);
		if (unlikely(!buf_state)) {
			buf_state = gve_alloc_buf_state(rx);
			if (unlikely(!buf_state))
				return -ENOMEM;

			if (unlikely(gve_alloc_qpl_page_dqo(rx, buf_state)))
				goto free_buf_state;
		}
	}
	desc->buf_id = cpu_to_le16(buf_state - rx->dqo.buf_states);
	desc->buf_addr = cpu_to_le64(buf_state->addr +
				     buf_state->page_info.page_offset);

	return 0;

free_buf_state:
	gve_free_buf_state(rx, buf_state);
	return -ENOMEM;
}