path: root/drivers/net/ethernet/sfc/rx_common.c

// SPDX-License-Identifier: GPL-2.0-only
/****************************************************************************
 * Driver for Solarflare network controllers and boards
 * Copyright 2018 Solarflare Communications Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation, incorporated herein by reference.
 */

#include "net_driver.h"
#include <linux/module.h>
#include <linux/iommu.h>
#include <net/rps.h>
#include "efx.h"
#include "nic.h"
#include "rx_common.h"

/* This is the percentage fill level below which new RX descriptors
 * will be added to the RX descriptor ring.
 */
static unsigned int rx_refill_threshold;
module_param(rx_refill_threshold, uint, 0444);
MODULE_PARM_DESC(rx_refill_threshold,
		 "RX descriptor ring refill threshold (%)");

/* RX maximum head room required.
 *
 * This must be at least 1 to prevent overflow, plus one packet-worth
 * to allow pipelined receives.
 */
#define EFX_RXD_HEAD_ROOM (1 + EFX_RX_MAX_FRAGS)

/* Check the RX page recycle ring for a page that can be reused. */
static struct page *efx_reuse_page(struct efx_rx_queue *rx_queue)
{
	struct efx_nic *efx = rx_queue->efx;
	struct efx_rx_page_state *state;
	unsigned int index;
	struct page *page;

	if (unlikely(!rx_queue->page_ring))
		return NULL;
	index = rx_queue->page_remove & rx_queue->page_ptr_mask;
	page = rx_queue->page_ring[index];
	if (page == NULL)
		return NULL;

	rx_queue->page_ring[index] = NULL;
	/* page_remove cannot exceed page_add. */
	if (rx_queue->page_remove != rx_queue->page_add)
		++rx_queue->page_remove;

	/* If page_count is 1 then we hold the only reference to this page. */
	if (page_count(page) == 1) {
		++rx_queue->page_recycle_count;
		return page;
	} else {
		state = page_address(page);
		dma_unmap_page(&efx->pci_dev->dev, state->dma_addr,
			       PAGE_SIZE << efx->rx_buffer_order,
			       DMA_FROM_DEVICE);
		put_page(page);
		++rx_queue->page_recycle_failed;
	}

	return NULL;
}

/* Attempt to recycle the page if there is an RX recycle ring; the page can
 * only be added if this is the final RX buffer, to prevent pages being used in
 * the descriptor ring and appearing in the recycle ring simultaneously.
 */
static void efx_recycle_rx_page(struct efx_channel *channel,
				struct efx_rx_buffer *rx_buf)
{
	struct efx_rx_queue *rx_queue = efx_channel_get_rx_queue(channel);
	struct efx_nic *efx = rx_queue->efx;
	struct page *page = rx_buf->page;
	unsigned int index;

	/* Only recycle the page after processing the final buffer. */
	if (!(rx_buf->flags & EFX_RX_BUF_LAST_IN_PAGE))
		return;

	index = rx_queue->page_add & rx_queue->page_ptr_mask;
	if (rx_queue->page_ring[index] == NULL) {
		unsigned int read_index = rx_queue->page_remove &
			rx_queue->page_ptr_mask;

		/* The next slot in the recycle ring is available, but
		 * increment page_remove if the read pointer currently
		 * points here.
		 */
		if (read_index == index)
			++rx_queue->page_remove;
		rx_queue->page_ring[index] = page;
		++rx_queue->page_add;
		return;
	}
	++rx_queue->page_recycle_full;
	efx_unmap_rx_buffer(efx, rx_buf);
	put_page(rx_buf->page);
}

/* Recycle the pages that are used by buffers that have just been received. */
void efx_recycle_rx_pages(struct efx_channel *channel,
			  struct efx_rx_buffer *rx_buf,
			  unsigned int n_frags)
{
	struct efx_rx_queue *rx_queue = efx_channel_get_rx_queue(channel);

	if (unlikely(!rx_queue->page_ring))
		return;

	do {
		efx_recycle_rx_page(channel, rx_buf);
		rx_buf = efx_rx_buf_next(rx_queue, rx_buf);
	} while (--n_frags);
}

void efx_discard_rx_packet(struct efx_channel *channel,
			   struct efx_rx_buffer *rx_buf,
			   unsigned int n_frags)
{
	struct efx_rx_queue *rx_queue = efx_channel_get_rx_queue(channel);

	efx_recycle_rx_pages(channel, rx_buf, n_frags);

	efx_free_rx_buffers(rx_queue, rx_buf, n_frags);
}

static void efx_init_rx_recycle_ring(struct efx_rx_queue *rx_queue)
{
	unsigned int bufs_in_recycle_ring, page_ring_size;
	struct efx_nic *efx = rx_queue->efx;

	bufs_in_recycle_ring = efx_rx_recycle_ring_size(efx);
	page_ring_size = roundup_pow_of_two(bufs_in_recycle_ring /
					    efx->rx_bufs_per_page);
	rx_queue->page_ring = kcalloc(page_ring_size,
				      sizeof(*rx_queue->page_ring), GFP_KERNEL);
	if (!rx_queue->page_ring)
		rx_queue->page_ptr_mask = 0;
	else
		rx_queue->page_ptr_mask = page_ring_size - 1;
}

static void efx_fini_rx_recycle_ring(struct efx_rx_queue *rx_queue)
{
	struct efx_nic *efx = rx_queue->efx;
	int i;

	if (unlikely(!rx_queue->page_ring))
		return;

	/* Unmap and release the pages in the recycle ring. Remove the ring. */
	for (i = 0; i <= rx_queue->page_ptr_mask; i++) {
		struct page *page = rx_queue