// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (C) 2021 in-tech smart charging GmbH
 *
 * driver is based on micrel/ks8851_spi.c
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/cache.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>

#include <linux/spi/spi.h>
#include <linux/of_net.h>

#define MSG_DEFAULT	(NETIF_MSG_DRV | NETIF_MSG_PROBE | NETIF_MSG_LINK | \
			 NETIF_MSG_TIMER)

#define DRV_NAME	"mse102x"

#define DET_CMD		0x0001
#define DET_SOF		0x0002
#define DET_DFT		0x55AA

#define CMD_SHIFT	12
#define CMD_RTS		(0x1 << CMD_SHIFT)
#define CMD_CTR		(0x2 << CMD_SHIFT)

#define CMD_MASK	GENMASK(15, CMD_SHIFT)
#define LEN_MASK	GENMASK(CMD_SHIFT - 1, 0)

#define DET_CMD_LEN	4
#define DET_SOF_LEN	2
#define DET_DFT_LEN	2

#define MIN_FREQ_HZ	6000000
#define MAX_FREQ_HZ	7142857

struct mse102x_stats {
	u64 xfer_err;
	u64 invalid_cmd;
	u64 invalid_ctr;
	u64 invalid_dft;
	u64 invalid_len;
	u64 invalid_rts;
	u64 invalid_sof;
	u64 tx_timeout;
};

static const char mse102x_gstrings_stats[][ETH_GSTRING_LEN] = {
	"SPI transfer errors",
	"Invalid command",
	"Invalid CTR",
	"Invalid DFT",
	"Invalid frame length",
	"Invalid RTS",
	"Invalid SOF",
	"TX timeout",
};

struct mse102x_net {
	struct net_device	*ndev;

	u8			rxd[8];
	u8			txd[8];

	u32			msg_enable ____cacheline_aligned;

	struct sk_buff_head	txq;
	struct mse102x_stats	stats;
};

struct mse102x_net_spi {
	struct mse102x_net	mse102x;
	struct mutex		lock;		/* Protect SPI frame transfer */
	struct work_struct	tx_work;
	struct spi_device	*spidev;
	struct spi_message	spi_msg;
	struct spi_transfer	spi_xfer;

#ifdef CONFIG_DEBUG_FS
	struct dentry		*device_root;
#endif
};

#define to_mse102x_spi(mse) container_of((mse), struct mse102x_net_spi, mse102x)

#ifdef CONFIG_DEBUG_FS

static int mse102x_info_show(struct seq_file *s, void *what)
{
	struct mse102x_net_spi *mses = s->private;

	seq_printf(s, "TX ring size        : %u\n",
		   skb_queue_len(&mses->mse102x.txq));

	seq_printf(s, "IRQ                 : %d\n",
		   mses->spidev->irq);

	seq_printf(s, "SPI effective speed : %lu\n",
		   (unsigned long)mses->spi_xfer.effective_speed_hz);
	seq_printf(s, "SPI mode            : %x\n",
		   mses->spidev->mode);

	return 0;
}
DEFINE_SHOW_ATTRIBUTE(mse102x_info);

static void mse102x_init_device_debugfs(struct mse102x_net_spi *mses)
{
	mses->device_root = debugfs_create_dir(dev_name(&mses->mse102x.ndev->dev),
					       NULL);

	debugfs_create_file("info", S_IFREG | 0444, mses->device_root, mses,
			    &mse102x_info_fops);
}

static void mse102x_remove_device_debugfs(struct mse102x_net_spi *mses)
{
	debugfs_remove_recursive(mses->device_root);
}

#else /* CONFIG_DEBUG_FS */

static void mse102x_init_device_debugfs(struct mse102x_net_spi *mses)
{
}

static void mse102x_remove_device_debugfs(struct mse102x_net_spi *mses)
{
}

#endif

/* SPI register read/write calls.
 *
 * All these calls issue SPI transactions to access the chip's registers. They
 * all require that the necessary lock is held to prevent accesses when the
 * chip is busy transferring packet data.
 */

static void mse102x_tx_cmd_spi(struct mse102x_net *mse, u16 cmd)
{
	struct mse102x_net_spi *mses = to_mse102x_spi(mse);
	struct spi_transfer *xfer = &mses->spi_xfer;
	struct spi_message *msg = &mses->spi_msg;
	__be16 txb[2];
	int ret;

	txb[0] = cpu_to_be16(DET_CMD);
	txb[1] = cpu_to_be16(cmd);

	xfer->tx_buf = txb;
	xfer->rx_buf = NULL;
	xfer->len = DET_CMD_LEN;

	ret = spi_sync(mses->spidev, msg);
	if (ret < 0) {
		netdev_err(mse->ndev, "%s: spi_sync() failed: %d\n",
			   __func__, ret);
		mse->stats.xfer_err++;
	}
}

static int mse102x_rx_cmd_spi(struct mse102x_net *mse, u8 *rxb)
{
	struct mse102x_net_spi *mses = to_mse102x_spi(mse);
	struct spi_transfer *xfer = &mses->spi_xfer;
	struct spi_message *msg = &mses->spi_msg;
	__be16 *txb = (__be16 *)mse->txd;
	__be16 *cmd = (__be16 *)mse->rxd;
	u8 *trx = mse->rxd;
	int ret;

	txb[0] = 0;
	txb[1] = 0;

	xfer->tx_buf = txb;
	xfer->rx_buf = trx;
	xfer->len = DET_CMD_LEN;

	ret = spi_sync(mses->spidev, msg);
	if (ret < 0) {
		netdev_err(mse->ndev, "%s: spi_sync() failed: %d\n",
			   __func__, ret);
		mse->stats.xfer_err++;
	} else if (*cmd != cpu_to_be16(DET_CMD)) {
		net_dbg_ratelimited("%s: Unexpected response (0x%04x)\n",
				    __func__, *cmd);
		mse->stats.invalid_cmd++;
		ret = -EIO;
	} else {
		memcpy(rxb, trx + 2, 2);
	}

	return ret;
}

static inline void mse102x_push_header(struct sk_buff *skb)
{
	__be16 *header = skb_push(skb, DET_SOF_LEN);

	*header = cpu_to_be16(DET_SOF);
}

static inline void mse102x_put_footer(struct sk_buff *skb)
{
	__be16 *footer = skb_put(skb, DET_DFT_LEN);

	*footer = cpu_to_be16(DET_DFT);
}

static int mse102x_tx_frame_spi(struct mse102x_net *mse, struct sk_buff *txp,
				unsigned int pad)
{
	struct mse102x_net_spi *mses = to_mse102x_spi(mse);
	struct spi_transfer *xfer = &mses->spi_xfer;
	struct spi_message *msg = &mses->spi_msg;
	struct sk_buff *tskb = NULL;
	int ret;

	netif_dbg(mse, tx_queued, mse->ndev, "%s: skb %p, %d@%p\n",
		  __func__, txp, txp->len, txp->data);

	if ((skb_headroom(txp) < DET_SOF_LEN) ||
	    (skb_tailroom(txp) < DET_DFT_LEN + pad)) {
		tskb = skb_copy_expand(txp, DET_SOF_LEN, DET_DFT_LEN + pad,
				       GFP_KERNEL);
		if (!tskb)
			return -ENOMEM;

		txp = tskb;
	}

	mse102x_push_header(txp);

	if (pad)
		skb_put_zero(txp, pad);

	mse102x_put_footer(txp);

	xfer->tx_buf = txp->data;
	xfer->rx_buf = NULL;
	xfer->len = txp->len;

	ret = spi_sync(mses->spidev, msg);
	if (ret < 0) {
		netdev_err(mse->ndev, "%s: spi_sync() failed: %d\n",
			   __func__, ret);
		mse->stats.xfer_err++;
	}

	dev_kfree_skb(tskb);

	return ret;
}

static int mse102x_rx_frame_spi(struct mse102x_net *mse, u8 *buff,
				unsigned int frame_len)
{
	struct mse102x_net_spi *mses = to_mse102x_spi(mse);
	struct spi_transfer *xfer = &mses->spi_xfer;
	struct spi_message *msg = &mses->spi_msg;
	__be16 *sof = (__be16 *)buff;
	__be16 *dft = (__be16 *)(buff + DET_SOF_LEN + frame_len);
	int ret;

	xfer->rx_buf = buff;
	xfer->tx_buf = NULL;
	xfer->len = DET_SOF_LEN + frame_len + DET_DFT_LEN;

	ret = spi_sync(mses->spidev, msg);
	if (ret < 0) {
		netdev_err(mse->ndev, "%s: spi_sync() failed: %d\n",
			   __func__, ret);
		mse->stats.xfer_err++;
	} else if (*sof != cpu_to_be16(DET_SOF)) {
		netdev_dbg(mse->ndev, "%s: SPI start of frame is invalid (0x%04x)\n",
			   __func__, *sof);
		mse->stats.invalid_sof++;
		ret = -EIO;
	} else if (*dft != cpu_to_be16(DET_DFT)) {
		netdev_dbg(mse->ndev, "%s: SPI frame tail is invalid (0x%04x)\n",
			   __func__, *dft);
		mse->stats.invalid_dft++;
		ret = -EIO;
	}

	return ret;
}

static void mse102x_dump_packet(const char *msg, int len, const char *data)
{
	printk(KERN_DEBUG ": %s - packet len:%d\n", msg, len);
	print_hex_dump(KERN_DEBUG, "pk data: ", DUMP_PREFIX_OFFSET, 16, 1,
		       data, len, true);
}

static void mse102x_rx_pkt_spi(struct mse102x_net *mse)
{
	struct sk_buff *skb;
	unsigned int rxalign;
	unsigned int rxlen;
	__be16 rx = 0;
	u16 cmd_resp;
	u8 *rxpkt;
	int ret;

	mse102x_tx_cmd_spi(mse, CMD_CTR);
	ret = mse102x_rx_cmd_spi(mse, (u8 *)&rx);
	cmd_resp = be16_to_cpu(rx);

	if (ret || ((cmd_resp & CMD_MASK) != CMD_RTS)) {
		usleep_range(50, 100);

		mse102x_tx_cmd_spi(mse, CMD_CTR);
		ret = mse102x_rx_cmd_spi(mse, (u8 *)&rx);
		if (ret)
			return;

		cmd_resp = be16_to_cpu(rx);
		if ((cmd_resp & CMD_MASK) != CMD_RTS) {
			net_dbg_ratelimited("%s: Unexpected response (0x%04x)\n",
					    __func__, cmd_resp);
			mse->stats.invalid_rts++;
			return;
		}

		net_dbg_ratelimited("%s: Unexpected response to first CMD\n",
				    __func__);
	}

	rxlen = cmd_resp & LEN_MASK;
	if (!rxlen) {
		net_dbg_ratelimited("%s: No frame length defined\n", __func__);
		mse->stats.invalid_len++;
		return;
	}

	rxalign = ALIGN(rxlen + DET_SOF_LEN + DET_DFT_LEN, 4);
	skb = netdev_alloc_skb_ip_align(mse->ndev, rxalign);
	if (!skb)
		return;

	/* 2 bytes Start of frame (before ethernet header)
	 * 2 bytes Data frame tail (after ethernet frame)
	 * They are copied, but ignored.
	 */
	rxpkt = skb_put(skb, rxlen) - DET_SOF_LEN;
	if (mse102x_rx_frame_spi(mse, rxpkt, rxlen)) {
		mse->ndev->stats.rx_errors++;
		dev_kfree_skb(skb);
		return;
	}

	if (netif_msg_pktdata(mse))
		mse102x_dump_packet(__func__, skb->len, skb->data);

	skb->protocol = eth_type_trans(skb, mse->ndev);
	netif_rx(skb);

	mse->ndev->stats.rx_packets++;
	mse->ndev->stats.rx_bytes += rxlen;
}

static int mse102x_tx_pkt_spi(struct mse102x_net *mse, struct sk_buff *txb,
			      unsigned long work_timeout)
{
	unsigned int pad = 0;
	__be16 rx = 0;
	u16 cmd_resp;
	int ret;
	bool first = true;

	if (txb->len < ETH_ZLEN)
		pad = ETH_ZLEN - txb->len;

	while (1) {
		mse102x_tx_cmd_spi(mse, CMD_RTS | (txb->len + pad));
		ret = mse102x_rx_cmd_spi(mse, (u8 *)&rx);
		cmd_resp = be16_to_cpu(rx);

		if (!ret) {
			/* ready to send frame ? */
			if (cmd_resp == CMD_CTR)
				break;

			net_dbg_ratelimited("%s: Unexpected response (0x%04x)\n",
					    __func__, cmd_resp);
			mse->stats.invalid_ctr++;
		}

		/* It's not predictable how long / many retries it takes to
		 * send at least one packet, so TX timeouts are possible.
		 * That's the reason why the netdev watchdog is not used here.
		 */
		if (time_after(jiffies, work_timeout))
			return -ETIMEDOUT;

		if (first) {
			/* throttle at first issue */
			netif_stop_queue(mse->ndev);
			/* fast retry */
			usleep_range(50, 100);
			first = false;
		} else {
			msleep(20);
		}
	}

	ret = mse102x_tx_frame_spi(mse, txb, pad);
	if (ret)
		net_dbg_ratelimited("%s: Failed to send (%d), drop frame\n",
				    __func__, ret);

	return ret;
}

#define TX_QUEUE_MAX 10

static void mse102x_tx_work(struct work_struct *work)
{
	/* Make sure timeout is sufficient to transfer TX_QUEUE_MAX frames */
	unsigned long work_timeout = jiffies + msecs_to_jiffies(1000);
	struct mse102x_net_spi *mses;
	struct mse102x_net *mse;
	struct sk_buff *txb;
	int ret = 0;

	mses = container_of(work, struct mse102x_net_spi, tx_work);
	mse = &mses->mse102x;

	while ((txb = skb_dequeue(&mse->txq))) {
		unsigned int len = max_t(unsigned int, txb->len, ETH_ZLEN);

		mutex_lock(&mses->lock);
		ret = mse102x_tx_pkt_spi(mse, txb, work_timeout);
		mutex_unlock(&mses->lock);
		if (ret) {
			mse->ndev->stats.tx_dropped++;
		} else {
			mse->ndev->stats.tx_bytes += len;
			mse->ndev->stats.tx_packets++;
		}

		dev_kfree_skb(txb);
	}

	if (ret == -ETIMEDOUT) {
		if (netif_msg_timer(mse))
			netdev_err_once(mse->ndev, "tx work timeout\n");

		mse->stats.tx_timeout++;
	}

	netif_wake_queue(mse->ndev);
}

static netdev_tx_t mse102x_start_xmit_spi(struct sk_buff *skb,
					  struct net_device *ndev)
{
	struct mse102x_net *mse = netdev_priv(ndev);
	struct mse102x_net_spi *mses = to_mse102x_spi(mse);

	netif_dbg(mse, tx_queued, ndev,
		  "%s: skb %p, %d@%p\n", __func__, skb, skb->len, skb->data);

	skb_queue_tail(&mse->txq, skb);

	if (skb_queue_len(&mse->txq) >= TX_QUEUE_MAX)
		netif_stop_queue(ndev);

	schedule_work(&mses->tx_work);

	return NETDEV_TX_OK;
}

static void mse102x_init_mac(struct mse102x_net *mse, struct device_node *np)
{
	struct net_device *ndev = mse->ndev;
	int ret = of_get_ethdev_address(np, ndev);

	if (ret) {
		eth_hw_addr_random(ndev);
		dev_warn(ndev->dev.parent, "Using random MAC address: %pM\n",
			 ndev->dev_addr);
	}
}

/* Assumption: this is called for every incoming packet */
static irqreturn_t mse102x_irq(int irq, void *_mse)
{
	struct mse102x_net *mse = _mse;
	struct mse102x_net_spi *mses = to_mse102x_spi(mse);

	mutex_lock(&mses->lock);
	mse102x_rx_pkt_spi(mse);
	mutex_unlock(&mses->lock);

	return IRQ_HANDLED;
}

static int mse102x_net_open(struct net_device *ndev)
{
	struct mse102x_net *mse = netdev_priv(ndev);
	int ret;

	ret = request_threaded_irq(ndev->irq, NULL, mse102x_irq, IRQF_ONESHOT,
				   ndev->name, mse);
	if (ret < 0) {
		netdev_err(ndev, "Failed to get irq: %d\n", ret);
		return ret;
	}

	netif_dbg(mse, ifup, ndev, "opening\n");

	netif_start_queue(ndev);

	netif_carrier_on(ndev);

	netif_dbg(mse, ifup, ndev, "network device up\n");

	return 0;
}

static int mse102x_net_stop(struct net_device *ndev)
{
	struct mse102x_net *mse = netdev_priv(ndev);
	struct mse102x_net_spi *mses = to_mse102x_spi(mse);

	netif_info(mse, ifdown, ndev, "shutting down\n");

	netif_carrier_off(mse->ndev);

	/* stop any outstanding work */
	flush_work(&mses->tx_work);

	netif_stop_queue(ndev);

	skb_queue_purge(&mse->txq);

	free_irq(ndev->irq, mse);

	return 0;
}

static const struct net_device_ops mse102x_netdev_ops = {
	.ndo_open		= mse102x_net_open,
	.ndo_stop		= mse102x_net_stop,
	.ndo_start_xmit		= mse102x_start_xmit_spi,
	.ndo_set_mac_address	= eth_mac_addr,
	.ndo_validate_addr	= eth_validate_addr,
};

/* ethtool support */

static void mse102x_get_drvinfo(struct net_device *ndev,
				struct ethtool_drvinfo *di)
{
	strscpy(di->driver, DRV_NAME, sizeof(di->driver));
	strscpy(di->bus_info, dev_name(ndev->dev.parent), sizeof(di->bus_info));
}

static u32 mse102x_get_msglevel(struct net_device *ndev)
{
	struct mse102x_net *mse = netdev_priv(ndev);

	return mse->msg_enable;
}

static void mse102x_set_msglevel(struct net_device *ndev, u32 to)
{
	struct mse102x_net *mse = netdev_priv(ndev);

	mse->msg_enable = to;
}

static void mse102x_get_ethtool_stats(struct net_device *ndev,
				      struct ethtool_stats *estats, u64 *data)
{
	struct mse102x_net *mse = netdev_priv(ndev);
	struct mse102x_stats *st = &mse->stats;

	memcpy(data, st, ARRAY_SIZE(mse102x_gstrings_stats) * sizeof(u64));
}

static void mse102x_get_strings(struct net_device *ndev, u32 stringset, u8 *buf)
{
	switch (stringset) {
	case ETH_SS_STATS:
		memcpy(buf, &mse102x_gstrings_stats,
		       sizeof(mse102x_gstrings_stats));
		break;
	default:
		WARN_ON(1);
		break;
	}
}

static int mse102x_get_sset_count(struct net_device *ndev, int sset)
{
	switch (sset) {
	case ETH_SS_STATS:
		return ARRAY_SIZE(mse102x_gstrings_stats);
	default:
		return -EINVAL;
	}
}

static const struct ethtool_ops mse102x_ethtool_ops = {
	.get_drvinfo		= mse102x_get_drvinfo,
	.get_link		= ethtool_op_get_link,
	.get_msglevel		= mse102x_get_msglevel,
	.set_msglevel		= mse102x_set_msglevel,
	.get_ethtool_stats	= mse102x_get_ethtool_stats,
	.get_strings		= mse102x_get_strings,
	.get_sset_count		= mse102x_get_sset_count,
};

/* driver bus management functions */

static int mse102x_suspend(struct device *dev)
{
	struct mse102x_net *mse = dev_get_drvdata(dev);
	struct net_device *ndev = mse->ndev;

	if (netif_running(ndev)) {
		netif_device_detach(ndev);
		mse102x_net_stop(ndev);
	}

	return 0;
}

static int mse102x_resume(struct device *dev)
{
	struct mse102x_net *mse = dev_get_drvdata(dev);
	struct net_device *ndev = mse->ndev;

	if (netif_running(ndev)) {
		mse102x_net_open(ndev);
		netif_device_attach(ndev);
	}

	return 0;
}

static DEFINE_SIMPLE_DEV_PM_OPS(mse102x_pm_ops, mse102x_suspend, mse102x_resume);

static int mse102x_probe_spi(struct spi_device *spi)
{
	struct device *dev = &spi->dev;
	struct mse102x_net_spi *mses;
	struct net_device *ndev;
	struct mse102x_net *mse;
	int ret;

	spi->bits_per_word = 8;
	spi->mode |= SPI_MODE_3;
	/* enforce minimum speed to ensure device functionality */
	spi->controller->min_speed_hz = MIN_FREQ_HZ;

	if (!spi->max_speed_hz)
		spi->max_speed_hz = MAX_FREQ_HZ;

	if (spi->max_speed_hz < MIN_FREQ_HZ ||
	    spi->max_speed_hz > MAX_FREQ_HZ) {
		dev_err(&spi->dev, "SPI max frequency out of range (min: %u, max: %u)\n",
			MIN_FREQ_HZ, MAX_FREQ_HZ);
		return -EINVAL;
	}

	ret = spi_setup(spi);
	if (ret < 0) {
		dev_err(&spi->dev, "Unable to setup SPI device: %d\n", ret);
		return ret;
	}

	ndev = devm_alloc_etherdev(dev, sizeof(struct mse102x_net_spi));
	if (!ndev)
		return -ENOMEM;

	ndev->needed_tailroom += ALIGN(DET_DFT_LEN, 4);
	ndev->needed_headroom += ALIGN(DET_SOF_LEN, 4);
	ndev->priv_flags &= ~IFF_TX_SKB_SHARING;
	ndev->tx_queue_len = 100;

	mse = netdev_priv(ndev);
	mses = to_mse102x_spi(mse);

	mses->spidev = spi;
	mutex_init(&mses->lock);
	INIT_WORK(&mses->tx_work, mse102x_tx_work);

	/* initialise pre-made spi transfer messages */
	spi_message_init(&mses->spi_msg);
	spi_message_add_tail(&mses->spi_xfer, &mses->spi_msg);

	ndev->irq = spi->irq;
	mse->ndev = ndev;

	/* set the default message enable */
	mse->msg_enable = netif_msg_init(-1, MSG_DEFAULT);

	skb_queue_head_init(&mse->txq);

	SET_NETDEV_DEV(ndev, dev);

	dev_set_drvdata(dev, mse);

	netif_carrier_off(mse->ndev);
	ndev->netdev_ops = &mse102x_netdev_ops;
	ndev->ethtool_ops = &mse102x_ethtool_ops;

	mse102x_init_mac(mse, dev->of_node);

	ret = register_netdev(ndev);
	if (ret) {
		dev_err(dev, "failed to register network device: %d\n", ret);
		return ret;
	}

	mse102x_init_device_debugfs(mses);

	return 0;
}

static void mse102x_remove_spi(struct spi_device *spi)
{
	struct mse102x_net *mse = dev_get_drvdata(&spi->dev);
	struct mse102x_net_spi *mses = to_mse102x_spi(mse);

	mse102x_remove_device_debugfs(mses);
	unregister_netdev(mse->ndev);
}

static const struct of_device_id mse102x_match_table[] = {
	{ .compatible = "vertexcom,mse1021" },
	{ .compatible = "vertexcom,mse1022" },
	{ }
};
MODULE_DEVICE_TABLE(of, mse102x_match_table);

static const struct spi_device_id mse102x_ids[] = {
	{ "mse1021" },
	{ "mse1022" },
	{ }
};
MODULE_DEVICE_TABLE(spi, mse102x_ids);

static struct spi_driver mse102x_driver = {
	.driver = {
		.name = DRV_NAME,
		.of_match_table = mse102x_match_table,
		.pm = pm_sleep_ptr(&mse102x_pm_ops),
	},
	.probe = mse102x_probe_spi,
	.remove = mse102x_remove_spi,
	.id_table = mse102x_ids,
};
module_spi_driver(mse102x_driver);

MODULE_DESCRIPTION("MSE102x Network driver");
MODULE_AUTHOR("Stefan Wahren <stefan.wahren@chargebyte.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:" DRV_NAME);