// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
/*
 *   Copyright (c) 2011, 2012, Qualcomm Atheros Communications Inc.
 *   Copyright (c) 2017, I2SE GmbH
 */

/*   This module implements the Qualcomm Atheros UART protocol for
 *   kernel-based UART device; it is essentially an Ethernet-to-UART
 *   serial converter;
 */

#include <linux/device.h>
#include <linux/errno.h>
#include <linux/etherdevice.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/of.h>
#include <linux/of_net.h>
#include <linux/sched.h>
#include <linux/serdev.h>
#include <linux/skbuff.h>
#include <linux/types.h>

#include "qca_7k_common.h"

#define QCAUART_DRV_VERSION "0.1.0"
#define QCAUART_DRV_NAME "qcauart"
#define QCAUART_TX_TIMEOUT (1 * HZ)

struct qcauart {
	struct net_device *net_dev;
	spinlock_t lock;			/* transmit lock */
	struct work_struct tx_work;		/* Flushes transmit buffer   */

	struct serdev_device *serdev;
	struct qcafrm_handle frm_handle;
	struct sk_buff *rx_skb;

	unsigned char *tx_head;			/* pointer to next XMIT byte */
	int tx_left;				/* bytes left in XMIT queue  */
	unsigned char *tx_buffer;
};

static size_t
qca_tty_receive(struct serdev_device *serdev, const u8 *data, size_t count)
{
	struct qcauart *qca = serdev_device_get_drvdata(serdev);
	struct net_device *netdev = qca->net_dev;
	struct net_device_stats *n_stats = &netdev->stats;
	size_t i;

	if (!qca->rx_skb) {
		qca->rx_skb = netdev_alloc_skb_ip_align(netdev,
							netdev->mtu +
							VLAN_ETH_HLEN);
		if (!qca->rx_skb) {
			n_stats->rx_errors++;
			n_stats->rx_dropped++;
			return 0;
		}
	}

	for (i = 0; i < count; i++) {
		s32 retcode;

		retcode = qcafrm_fsm_decode(&qca->frm_handle,
					    qca->rx_skb->data,
					    skb_tailroom(qca->rx_skb),
					    data[i]);

		switch (retcode) {
		case QCAFRM_GATHER:
		case QCAFRM_NOHEAD:
			break;
		case QCAFRM_NOTAIL:
			netdev_dbg(netdev, "recv: no RX tail\n");
			n_stats->rx_errors++;
			n_stats->rx_dropped++;
			break;
		case QCAFRM_INVLEN:
			netdev_dbg(netdev, "recv: invalid RX length\n");
			n_stats->rx_errors++;
			n_stats->rx_dropped++;
			break;
		default:
			n_stats->rx_packets++;
			n_stats->rx_bytes += retcode;
			skb_put(qca->rx_skb, retcode);
			qca->rx_skb->protocol = eth_type_trans(
						qca->rx_skb, qca->rx_skb->dev);
			skb_checksum_none_assert(qca->rx_skb);
			netif_rx(qca->rx_skb);
			qca->rx_skb = netdev_alloc_skb_ip_align(netdev,
								netdev->mtu +
								VLAN_ETH_HLEN);
			if (!qca->rx_skb) {
				netdev_dbg(netdev, "recv: out of RX resources\n");
				n_stats->rx_errors++;
				return i;
			}
		}
	}

	return i;
}

/* Write out any remaining transmit buffer. Scheduled when tty is writable */
static void qcauart_transmit(struct work_struct *work)
{
	struct qcauart *qca = container_of(work, struct qcauart, tx_work);
	struct net_device_stats *n_stats = &qca->net_dev->stats;
	int written;

	spin_lock_bh(&qca->lock);

	/* First make sure we're connected. */
	if (!netif_running(qca->net_dev)) {
		spin_unlock_bh(&qca->lock);
		return;
	}

	if (qca->tx_left <= 0)  {
		/* Now serial buffer is almost free & we can start
		 * transmission of another packet
		 */
		n_stats->tx_packets++;
		spin_unlock_bh(&qca->lock);
		netif_wake_queue(qca->net_dev);
		return;
	}

	written = serdev_device_write_buf(qca->serdev, qca->tx_head,
					  qca->tx_left);
	if (written > 0) {
		qca->tx_left -= written;
		qca->tx_head += written;
	}
	spin_unlock_bh(&qca->lock);
}

/* Called by the driver when there's room for more data.
 * Schedule the transmit.
 */
static void qca_tty_wakeup(struct serdev_device *serdev)
{
	struct qcauart *qca = serdev_device_get_drvdata(serdev);

	schedule_work(&qca->tx_work);
}

static const struct serdev_device_ops qca_serdev_ops = {
	.receive_buf = qca_tty_receive,
	.write_wakeup = qca_tty_wakeup,
};

static int qcauart_netdev_open(struct net_device *dev)
{
	struct qcauart *qca = netdev_priv(dev);

	netif_start_queue(qca->net_dev);

	return 0;
}

static int qcauart_netdev_close(struct net_device *dev)
{
	struct qcauart *qca = netdev_priv(dev);

	netif_stop_queue(dev);
	flush_work(&qca->tx_work);

	spin_lock_bh(&qca->lock);
	qca->tx_left = 0;
	spin_unlock_bh(&qca->lock);

	return 0;
}

static netdev_tx_t
qcauart_netdev_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct net_device_stats *n_stats = &dev->stats;
	struct qcauart *qca = netdev_priv(dev);
	u8 pad_len = 0;
	int written;
	u8 *pos;

	spin_lock(&qca->lock);

	WARN_ON(qca->tx_left);

	if (!netif_running(dev))  {
		spin_unlock(&qca->lock);
		netdev_warn(qca->net_dev, "xmit: iface is down\n");
		goto out;
	}

	pos = qca->tx_buffer;

	if (skb->len < QCAFRM_MIN_LEN)
		pad_len = QCAFRM_MIN_LEN - skb->len;

	pos += qcafrm_create_header(pos, skb->len + pad_len);

	memcpy(pos, skb->data, skb->len);
	pos += skb->len;

	if (pad_len) {
		memset(pos, 0, pad_len);
		pos += pad_len;
	}

	pos += qcafrm_create_footer(pos);

	netif_stop_queue(qca->net_dev);

	written = serdev_device_write_buf(qca->serdev, qca->tx_buffer,
					  pos - qca->tx_buffer);
	if (written > 0) {
		qca->tx_left = (pos - qca->tx_buffer) - written;
		qca->tx_head = qca->tx_buffer + written;
		n_stats->tx_bytes += written;
	}
	spin_unlock(&qca->lock);

	netif_trans_update(dev);
out:
	dev_kfree_skb_any(skb);
	return NETDEV_TX_OK;
}

static void qcauart_netdev_tx_timeout(struct net_device *dev, unsigned int txqueue)
{
	struct qcauart *qca = netdev_priv(dev);

	netdev_info(qca->net_dev, "Transmit timeout at %ld, latency %ld\n",
		    jiffies, dev_trans_start(dev));
	dev->stats.tx_errors++;
	dev->stats.tx_dropped++;
}

static int qcauart_netdev_init(struct net_device *dev)
{
	struct qcauart *qca = netdev_priv(dev);
	size_t len;

	/* Finish setting up the device info. */
	dev->mtu = QCAFRM_MAX_MTU;
	dev->type = ARPHRD_ETHER;

	len = QCAFRM_HEADER_LEN + QCAFRM_MAX_LEN + QCAFRM_FOOTER_LEN;
	qca->tx_buffer = devm_kmalloc(&qca->serdev->dev, len, GFP_KERNEL);
	if (!qca->tx_buffer)
		return -ENOMEM;

	qca->rx_skb = netdev_alloc_skb_ip_align(qca->net_dev,
						qca->net_dev->mtu +
						VLAN_ETH_HLEN);
	if (!qca->rx_skb)
		return -ENOBUFS;

	return 0;
}

static void qcauart_netdev_uninit(struct net_device *dev)
{
	struct qcauart *qca = netdev_priv(dev);

	dev_kfree_skb(qca->rx_skb);
}

static const struct net_device_ops qcauart_netdev_ops = {
	.ndo_init = qcauart_netdev_init,
	.ndo_uninit = qcauart_netdev_uninit,
	.ndo_open = qcauart_netdev_open,
	.ndo_stop = qcauart_netdev_close,
	.ndo_start_xmit = qcauart_netdev_xmit,
	.ndo_set_mac_address = eth_mac_addr,
	.ndo_tx_timeout = qcauart_netdev_tx_timeout,
	.ndo_validate_addr = eth_validate_addr,
};

static void qcauart_netdev_setup(struct net_device *dev)
{
	dev->netdev_ops = &qcauart_netdev_ops;
	dev->watchdog_timeo = QCAUART_TX_TIMEOUT;
	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
	dev->tx_queue_len = 100;

	/* MTU range: 46 - 1500 */
	dev->min_mtu = QCAFRM_MIN_MTU;
	dev->max_mtu = QCAFRM_MAX_MTU;
}

static const struct of_device_id qca_uart_of_match[] = {
	{
	 .compatible = "qca,qca7000",
	},
	{}
};
MODULE_DEVICE_TABLE(of, qca_uart_of_match);

static int qca_uart_probe(struct serdev_device *serdev)
{
	struct net_device *qcauart_dev = alloc_etherdev(sizeof(struct qcauart));
	struct qcauart *qca;
	u32 speed = 115200;
	int ret;

	if (!qcauart_dev)
		return -ENOMEM;

	qcauart_netdev_setup(qcauart_dev);
	SET_NETDEV_DEV(qcauart_dev, &serdev->dev);

	qca = netdev_priv(qcauart_dev);
	if (!qca) {
		pr_err("qca_uart: Fail to retrieve private structure\n");
		ret = -ENOMEM;
		goto free;
	}
	qca->net_dev = qcauart_dev;
	qca->serdev = serdev;
	qcafrm_fsm_init_uart(&qca->frm_handle);

	spin_lock_init(&qca->lock);
	INIT_WORK(&qca->tx_work, qcauart_transmit);

	of_property_read_u32(serdev->dev.of_node, "current-speed", &speed);

	ret = of_get_ethdev_address(serdev->dev.of_node, qca->net_dev);
	if (ret) {
		eth_hw_addr_random(qca->net_dev);
		dev_info(&serdev->dev, "Using random MAC address: %pM\n",
			 qca->net_dev->dev_addr);
	}

	netif_carrier_on(qca->net_dev);
	serdev_device_set_drvdata(serdev, qca);
	serdev_device_set_client_ops(serdev, &qca_serdev_ops);

	ret = serdev_device_open(serdev);
	if (ret) {
		dev_err(&serdev->dev, "Unable to open device %s\n",
			qcauart_dev->name);
		goto free;
	}

	speed = serdev_device_set_baudrate(serdev, speed);
	dev_info(&serdev->dev, "Using baudrate: %u\n", speed);

	serdev_device_set_flow_control(serdev, false);

	ret = register_netdev(qcauart_dev);
	if (ret) {
		dev_err(&serdev->dev, "Unable to register net device %s\n",
			qcauart_dev->name);
		serdev_device_close(serdev);
		cancel_work_sync(&qca->tx_work);
		goto free;
	}

	return 0;

free:
	free_netdev(qcauart_dev);
	return ret;
}

static void qca_uart_remove(struct serdev_device *serdev)
{
	struct qcauart *qca = serdev_device_get_drvdata(serdev);

	unregister_netdev(qca->net_dev);

	/* Flush any pending characters in the driver. */
	serdev_device_close(serdev);
	cancel_work_sync(&qca->tx_work);

	free_netdev(qca->net_dev);
}

static struct serdev_device_driver qca_uart_driver = {
	.probe = qca_uart_probe,
	.remove = qca_uart_remove,
	.driver = {
		.name = QCAUART_DRV_NAME,
		.of_match_table = qca_uart_of_match,
	},
};

module_serdev_device_driver(qca_uart_driver);

MODULE_DESCRIPTION("Qualcomm Atheros QCA7000 UART Driver");
MODULE_AUTHOR("Qualcomm Atheros Communications");
MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_VERSION(QCAUART_DRV_VERSION);