/*
 * drivers/net/ethernet/ec_bhf.c
 *
 * Copyright (C) 2014 Darek Marcinkiewicz <reksio@newterm.pl>
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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 is a driver for EtherCAT master module present on CCAT FPGA.
 * Those can be found on Bechhoff CX50xx industrial PCs.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/pci.h>
#include <linux/init.h>

#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/ip.h>
#include <linux/skbuff.h>
#include <linux/hrtimer.h>
#include <linux/interrupt.h>
#include <linux/stat.h>

#define TIMER_INTERVAL_NSEC	20000

#define INFO_BLOCK_SIZE		0x10
#define INFO_BLOCK_TYPE		0x0
#define INFO_BLOCK_REV		0x2
#define INFO_BLOCK_BLK_CNT	0x4
#define INFO_BLOCK_TX_CHAN	0x4
#define INFO_BLOCK_RX_CHAN	0x5
#define INFO_BLOCK_OFFSET	0x8

#define EC_MII_OFFSET		0x4
#define EC_FIFO_OFFSET		0x8
#define EC_MAC_OFFSET		0xc

#define MAC_FRAME_ERR_CNT	0x0
#define MAC_RX_ERR_CNT		0x1
#define MAC_CRC_ERR_CNT		0x2
#define MAC_LNK_LST_ERR_CNT	0x3
#define MAC_TX_FRAME_CNT	0x10
#define MAC_RX_FRAME_CNT	0x14
#define MAC_TX_FIFO_LVL		0x20
#define MAC_DROPPED_FRMS	0x28
#define MAC_CONNECTED_CCAT_FLAG	0x78

#define MII_MAC_ADDR		0x8
#define MII_MAC_FILT_FLAG	0xe
#define MII_LINK_STATUS		0xf

#define FIFO_TX_REG		0x0
#define FIFO_TX_RESET		0x8
#define FIFO_RX_REG		0x10
#define FIFO_RX_ADDR_VALID	(1u << 31)
#define FIFO_RX_RESET		0x18

#define DMA_CHAN_OFFSET		0x1000
#define DMA_CHAN_SIZE		0x8

#define DMA_WINDOW_SIZE_MASK	0xfffffffc

#define ETHERCAT_MASTER_ID	0x14

static struct pci_device_id ids[] = {
	{ PCI_DEVICE(0x15ec, 0x5000), },
	{ 0, }
};
MODULE_DEVICE_TABLE(pci, ids);

struct rx_header {
#define RXHDR_NEXT_ADDR_MASK	0xffffffu
#define RXHDR_NEXT_VALID	(1u << 31)
	__le32 next;
#define RXHDR_NEXT_RECV_FLAG	0x1
	__le32 recv;
#define RXHDR_LEN_MASK		0xfffu
	__le16 len;
	__le16 port;
	__le32 reserved;
	u8 timestamp[8];
} __packed;

#define PKT_PAYLOAD_SIZE	0x7e8
struct rx_desc {
	struct rx_header header;
	u8 data[PKT_PAYLOAD_SIZE];
} __packed;

struct tx_header {
	__le16 len;
#define TX_HDR_PORT_0		0x1
#define TX_HDR_PORT_1		0x2
	u8 port;
	u8 ts_enable;
#define TX_HDR_SENT		0x1
	__le32 sent;
	u8 timestamp[8];
} __packed;

struct tx_desc {
	struct tx_header header;
	u8 data[PKT_PAYLOAD_SIZE];
} __packed;

#define FIFO_SIZE		64

static long polling_frequency = TIMER_INTERVAL_NSEC;

struct bhf_dma {
	u8 *buf;
	size_t len;
	dma_addr_t buf_phys;

	u8 *alloc;
	size_t alloc_len;
	dma_addr_t alloc_phys;
};

struct ec_bhf_priv {
	struct net_device *net_dev;
	struct pci_dev *dev;

	void __iomem *io;
	void __iomem *dma_io;

	struct hrtimer hrtimer;

	int tx_dma_chan;
	int rx_dma_chan;
	void __iomem *ec_io;
	void __iomem *fifo_io;
	void __iomem *mii_io;
	void __iomem *mac_io;

	struct bhf_dma rx_buf;
	struct rx_desc *rx_descs;
	int rx_dnext;
	int rx_dcount;

	struct bhf_dma tx_buf;
	struct tx_desc *tx_descs;
	int tx_dcount;
	int tx_dnext;

	u64 stat_rx_bytes;
	u64 stat_tx_bytes;
};

#define PRIV_TO_DEV(priv) (&(priv)->dev->dev)

static void ec_bhf_reset(struct ec_bhf_priv *priv)
{
	iowrite8(0, priv->mac_io + MAC_FRAME_ERR_CNT);
	iowrite8(0, priv->mac_io + MAC_RX_ERR_CNT);
	iowrite8(0, priv->mac_io + MAC_CRC_ERR_CNT);
	iowrite8(0, priv->mac_io + MAC_LNK_LST_ERR_CNT);
	iowrite32(0, priv->mac_io + MAC_TX_FRAME_CNT);
	iowrite32(0, priv->mac_io + MAC_RX_FRAME_CNT);
	iowrite8(0, priv->mac_io + MAC_DROPPED_FRMS);

	iowrite8(0, priv->fifo_io + FIFO_TX_RESET);
	iowrite8(0, priv->fifo_io + FIFO_RX_RESET);

	iowrite8(0, priv->mac_io + MAC_TX_FIFO_LVL);
}

static void ec_bhf_send_packet(struct ec_bhf_priv *priv, struct tx_desc *desc)
{
	u32 len = le16_to_cpu(desc->header.len) + sizeof(desc->header);
	u32 addr = (u8 *)desc - priv->tx_buf.buf;

	iowrite32((ALIGN(len, 8) << 24) | addr, priv->fifo_io + FIFO_TX_REG);
}

static int ec_bhf_desc_sent(struct tx_desc *desc)
{
	return le32_to_cpu(desc->header.sent) & TX_HDR_SENT;
}

static void ec_bhf_process_tx(struct ec_bhf_priv *priv)
{
	if (unlikely(netif_queue_stopped(priv->net_dev))) {
		/* Make sure that we perceive changes to tx_dnext. */
		smp_rmb();

		if (ec_bhf_desc_sent(&priv->tx_descs[priv->tx_dnext]))
			netif_wake_queue(priv->net_dev);
	}
}

static int ec_bhf_pkt_received(struct rx_desc *desc)
{
	return le32_to_cpu(desc->header.recv) & RXHDR_NEXT_RECV_FLAG;
}

static void ec_bhf_add_rx_desc(struct ec_bhf_priv *priv, struct rx_desc *desc)
{
	iowrite32(FIFO_RX_ADDR_VALID | ((u8 *)(desc) - priv->rx_buf.buf),
		  priv->fifo_io + FIFO_RX_REG);
}

static void ec_bhf_process_rx(struct ec_bhf_priv *priv)
{
	struct rx_desc *desc = &priv->rx_descs[priv->rx_dnext];

	while (ec_bhf_pkt_received(desc)) {
		int pkt_size = (le16_to_cpu(desc->header.len) &
			       RXHDR_LEN_MASK) - sizeof(struct rx_header) - 4;
		u8 *data = desc->data;
		struct sk_buff *skb;

		skb = netdev_alloc_skb_ip_align(priv->net_dev, pkt_size);
		if (skb) {
			memcpy(skb_put(skb, pkt_size), data, pkt_size);
			skb->protocol = eth_type_trans(skb, priv->net_dev);
			priv->stat_rx_bytes += pkt_size;

			netif_rx(skb);
		} else {
			dev_err_ratelimited(PRIV_TO_DEV(priv),
					    "Couldn't allocate a skb_buff for a packet of size %u\n",
					    pkt_size);
		}

		desc->header.recv = 0;

		ec_bhf_add_rx_desc(priv, desc);

		priv->rx_dnext = (priv->rx_dnext + 1) % priv->rx_dcount;
		desc = &priv->rx_descs[priv->rx_dnext];
	}
}

static enum hrtimer_restart ec_bhf_timer_fun(struct hrtimer *timer)
{
	struct ec_bhf_priv *priv = container_of(timer, struct ec_bhf_priv,
						hrtimer);
	ec_bhf_process_rx(priv);
	ec_bhf_process_tx(priv);

	if (!netif_running(priv->net_dev))
		return HRTIMER_NORESTART;

	hrtimer_forward_now(timer, ktime_set(0, polling_frequency));
	return HRTIMER_RESTART;
}

static int ec_bhf_setup_offsets(struct ec_bhf_priv *priv)
{
	struct device *dev = PRIV_TO_DEV(priv);
	unsigned block_count, i;
	void __iomem *ec_info;

	block_count = ioread8(priv->io + INFO_BLOCK_BLK_CNT);
	for (i = 0; i < block_count; i++) {
		u16 type = ioread16(priv->io + i * INFO_BLOCK_SIZE +
				    INFO_BLOCK_TYPE);
		if (type == ETHERCAT_MASTER_ID)
			break;
	}
	if (i == block_count) {
		dev_err(dev, "EtherCAT master with DMA block not found\n");
		return -ENODEV;
	}

	ec_info = priv->io + i * INFO_BLOCK_SIZE;

	priv->tx_dma_chan = ioread8(ec_info + INFO_BLOCK_TX_CHAN);
	priv->rx_dma_chan = ioread8(ec_info + INFO_BLOCK_RX_CHAN);

	priv->ec_io = priv->io + ioread32(ec_info + INFO_BLOCK_OFFSET);
	priv->mii_io = priv->ec_io + ioread32(priv->ec_io + EC_MII_OFFSET);
	priv->fifo_io = priv->ec_io + ioread32(priv->ec_io + EC_FIFO_OFFSET);
	priv->mac_io = priv->ec_io + ioread32(priv->ec_io + EC_MAC_OFFSET);

	return 0;
}

static netdev_tx_t ec_bhf_start_xmit(struct sk_buff *skb,
				     struct net_device *net_dev)
{
	struct ec_bhf_priv *priv = netdev_priv(net_dev);
	struct tx_desc *desc;
	unsigned len;

	desc = &priv->tx_descs[priv->tx_dnext];

	skb_copy_and_csum_dev(skb, desc->data);
	len = skb->len;

	memset(&desc->header, 0, sizeof(desc->header));
	desc->header.len = cpu_to_le16(len);
	desc->header.port = TX_HDR_PORT_0;

	ec_bhf_send_packet(priv, desc);

	priv->tx_dnext = (priv->tx_dnext + 1) % priv->tx_dcount;

	if (!ec_bhf_desc_sent(&priv->tx_descs[priv->tx_dnext])) {
		/* Make sure that updates to tx_dnext are perceived
		 * by timer routine.
		 */
		smp_wmb();

		netif_stop_queue(net_dev);
	}

	priv->stat_tx_bytes += len;

	dev_kfree_skb(skb);

	return NETDEV_TX_OK;
}

static int ec_bhf_alloc_dma_mem(struct ec_bhf_priv *priv,
				struct bhf_dma *buf,
				int channel,
				int size)
{
	int offset = channel * DMA_CHAN_SIZE + DMA_CHAN_OFFSET;
	struct device *dev = PRIV_TO_DEV(priv);
	u32 mask;

	iowrite32(0xffffffff, priv->dma_io + offset);

	mask = ioread32(priv->dma_io + offset);
	mask &= DMA_WINDOW_SIZE_MASK;

	/* We want to allocate a chunk of memory that is:
	 * - aligned to the mask we just read
	 * - is of size 2^mask bytes (at most)
	 * In order to ensure that we will allocate buffer of
	 * 2 * 2^mask bytes.
	 */
	buf->len = min_t(int, ~mask + 1, size);
	buf->alloc_len = 2 * buf->len;

	buf->alloc = dma_alloc_coherent(dev, buf->alloc_len, &buf->alloc_phys,
					GFP_KERNEL);
	if (buf->alloc == NULL) {
		dev_err(dev, "Failed to allocate buffer\n");
		return -ENOMEM;
	}

	buf->buf_phys = (buf->alloc_phys + buf->len) & mask;
	buf->buf = buf->alloc + (buf->buf_phys - buf->alloc_phys);

	iowrite32(0, priv->dma_io + offset + 4);
	iowrite32(buf->buf_phys, priv->dma_io + offset);

	return 0;
}

static void ec_bhf_setup_tx_descs(struct ec_bhf_priv *priv)
{
	int i = 0;

	priv->tx_dcount = priv->tx_buf.len / sizeof(struct tx_desc);
	priv->tx_descs = (struct tx_desc *)priv->tx_buf.buf;
	priv->tx_dnext = 0;

	for (i = 0; i < priv->tx_dcount; i++)
		priv->tx_descs[i].header.sent = cpu_to_le32(TX_HDR_SENT);
}

static void ec_bhf_setup_rx_descs(struct ec_bhf_priv *priv)
{
	int i;

	priv->rx_dcount = priv->rx_buf.len / sizeof(struct rx_desc);
	priv->rx_descs = (struct rx_desc *)priv->rx_buf.buf;
	priv->rx_dnext = 0;

	for (i = 0; i < priv->rx_dcount; i++) {
		struct rx_desc *desc = &priv->rx_descs[i];
		u32 next;

		if (i != priv->rx_dcount - 1)
			next = (u8 *)(desc + 1) - priv->rx_buf.buf;
		else
			next = 0;
		next |= RXHDR_NEXT_VALID;
		desc->header.next = cpu_to_le32(next);
		desc->header.recv = 0;
		ec_bhf_add_rx_desc(priv, desc);
	}
}

static int ec_bhf_open(struct net_device *net_dev)
{
	struct ec_bhf_priv *priv = netdev_priv(net_dev);
	struct device *dev = PRIV_TO_DEV(priv);
	int err = 0;

	ec_bhf_reset(priv);

	err = ec_bhf_alloc_dma_mem(priv, &priv->rx_buf, priv->rx_dma_chan,
				   FIFO_SIZE * sizeof(struct rx_desc));
	if (err) {
		dev_err(dev, "Failed to allocate rx buffer\n");
		goto out;
	}
	ec_bhf_setup_rx_descs(priv);

	err = ec_bhf_alloc_dma_mem(priv, &priv->tx_buf, priv->tx_dma_chan,
				   FIFO_SIZE * sizeof(struct tx_desc));
	if (err) {
		dev_err(dev, "Failed to allocate tx buffer\n");
		goto error_rx_free;
	}
	iowrite8(0, priv->mii_io + MII_MAC_FILT_FLAG);
	ec_bhf_setup_tx_descs(priv);

	netif_start_queue(net_dev);

	hrtimer_init(&priv->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	priv->hrtimer.function = ec_bhf_timer_fun;
	hrtimer_start(&priv->hrtimer, ktime_set(0, polling_frequency),
		      HRTIMER_MODE_REL);

	return 0;

error_rx_free:
	dma_free_coherent(dev, priv->rx_buf.alloc_len, priv->rx_buf.alloc,
			  priv->rx_buf.alloc_len);
out:
	return err;
}

static int ec_bhf_stop(struct net_device *net_dev)
{
	struct ec_bhf_priv *priv = netdev_priv(net_dev);
	struct device *dev = PRIV_TO_DEV(priv);

	hrtimer_cancel(&priv->hrtimer);

	ec_bhf_reset(priv);

	netif_tx_disable(net_dev);

	dma_free_coherent(dev, priv->tx_buf.alloc_len,
			  priv->tx_buf.alloc, priv->tx_buf.alloc_phys);
	dma_free_coherent(dev, priv->rx_buf.alloc_len,
			  priv->rx_buf.alloc, priv->rx_buf.alloc_phys);

	return 0;
}

static struct rtnl_link_stats64 *
ec_bhf_get_stats(struct net_device *net_dev,
		 struct rtnl_link_stats64 *stats)
{
	struct ec_bhf_priv *priv = netdev_priv(net_dev);

	stats->rx_errors = ioread8(priv->mac_io + MAC_RX_ERR_CNT) +
				ioread8(priv->mac_io + MAC_CRC_ERR_CNT) +
				ioread8(priv->mac_io + MAC_FRAME_ERR_CNT);
	stats->rx_packets = ioread32(priv->mac_io + MAC_RX_FRAME_CNT);
	stats->tx_packets = ioread32(priv->mac_io + MAC_TX_FRAME_CNT);
	stats->rx_dropped = ioread8(priv->mac_io + MAC_DROPPED_FRMS);

	stats->tx_bytes = priv->stat_tx_bytes;
	stats->rx_bytes = priv->stat_rx_bytes;

	return stats;
}

static const struct net_device_ops ec_bhf_netdev_ops = {
	.ndo_start_xmit		= ec_bhf_start_xmit,
	.ndo_open		= ec_bhf_open,
	.ndo_stop		= ec_bhf_stop,
	.ndo_get_stats64	= ec_bhf_get_stats,
	.ndo_change_mtu		= eth_change_mtu,
	.ndo_validate_addr	= eth_validate_addr,
	.ndo_set_mac_address	= eth_mac_addr
};

static int ec_bhf_probe(struct pci_dev *dev, const struct pci_device_id *id)
{
	struct net_device *net_dev;
	struct ec_bhf_priv *priv;
	void __iomem *dma_io;
	void __iomem *io;
	int err = 0;

	err = pci_enable_device(dev);
	if (err)
		return err;

	pci_set_master(dev);

	err = pci_set_dma_mask(dev, DMA_BIT_MASK(32));
	if (err) {
		dev_err(&dev->dev,
			"Required dma mask not supported, failed to initialize device\n");
		err = -EIO;
		goto err_disable_dev;
	}

	err = pci_set_consistent_dma_mask(dev, DMA_BIT_MASK(32));
	if (err) {
		dev_err(&dev->dev,
			"Required dma mask not supported, failed to initialize device\n");
		goto err_disable_dev;
	}

	err = pci_request_regions(dev, "ec_bhf");
	if (err) {
		dev_err(&dev->dev, "Failed to request pci memory regions\n");
		goto err_disable_dev;
	}

	io = pci_iomap(dev, 0, 0);
	if (!io) {
		dev_err(&dev->dev, "Failed to map pci card memory bar 0");
		err = -EIO;
		goto err_release_regions;
	}

	dma_io = pci_iomap(dev, 2, 0);
	if (!dma_io) {
		dev_err(&dev->dev, "Failed to map pci card memory bar 2");
		err = -EIO;
		goto err_unmap;
	}

	net_dev = alloc_etherdev(sizeof(struct ec_bhf_priv));
	if (net_dev == NULL) {
		err = -ENOMEM;
		goto err_unmap_dma_io;
	}

	pci_set_drvdata(dev, net_dev);
	SET_NETDEV_DEV(net_dev, &dev->dev);

	net_dev->features = 0;
	net_dev->flags |= IFF_NOARP;

	net_dev->netdev_ops = &ec_bhf_netdev_ops;

	priv = netdev_priv(net_dev);
	priv->net_dev = net_dev;
	priv->io = io;
	priv->dma_io = dma_io;
	priv->dev = dev;

	err = ec_bhf_setup_offsets(priv);
	if (err < 0)
		goto err_free_net_dev;

	memcpy_fromio(net_dev->dev_addr, priv->mii_io + MII_MAC_ADDR, 6);

	err = register_netdev(net_dev);
	if (err < 0)
		goto err_free_net_dev;

	return 0;

err_free_net_dev:
	free_netdev(net_dev);
err_unmap_dma_io:
	pci_iounmap(dev, dma_io);
err_unmap:
	pci_iounmap(dev, io);
err_release_regions:
	pci_release_regions(dev);
err_disable_dev:
	pci_clear_master(dev);
	pci_disable_device(dev);

	return err;
}

static void ec_bhf_remove(struct pci_dev *dev)
{
	struct net_device *net_dev = pci_get_drvdata(dev);
	struct ec_bhf_priv *priv = netdev_priv(net_dev);

	unregister_netdev(net_dev);
	free_netdev(net_dev);

	pci_iounmap(dev, priv->dma_io);
	pci_iounmap(dev, priv->io);
	pci_release_regions(dev);
	pci_clear_master(dev);
	pci_disable_device(dev);
}

static struct pci_driver pci_driver = {
	.name		= "ec_bhf",
	.id_table	= ids,
	.probe		= ec_bhf_probe,
	.remove		= ec_bhf_remove,
};
module_pci_driver(pci_driver);

module_param(polling_frequency, long, S_IRUGO);
MODULE_PARM_DESC(polling_frequency, "Polling timer frequency in ns");

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dariusz Marcinkiewicz <reksio@newterm.pl>");