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/* uart_h5.c - UART based Bluetooth driver */

/*
 * Copyright (c) 2015-2016 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <errno.h>
#include <stddef.h>

#include <zephyr.h>

#include <init.h>
#include <drivers/uart.h>
#include <sys/util.h>
#include <sys/byteorder.h>
#include <debug/stack.h>
#include <sys/printk.h>
#include <string.h>

#include <bluetooth/bluetooth.h>
#include <bluetooth/hci.h>
#include <bluetooth/hci_driver.h>

#define BT_DBG_ENABLED IS_ENABLED(CONFIG_BT_DEBUG_HCI_DRIVER)
#define LOG_MODULE_NAME bt_driver
#include "common/log.h"

#include "../util.h"

static K_THREAD_STACK_DEFINE(tx_stack, 256);
static K_THREAD_STACK_DEFINE(rx_stack, 256);

static struct k_thread tx_thread_data;
static struct k_thread rx_thread_data;

static struct k_delayed_work ack_work;
static struct k_delayed_work retx_work;

#define HCI_3WIRE_ACK_PKT	0x00
#define HCI_COMMAND_PKT		0x01
#define HCI_ACLDATA_PKT		0x02
#define HCI_SCODATA_PKT		0x03
#define HCI_EVENT_PKT		0x04
#define HCI_3WIRE_LINK_PKT	0x0f
#define HCI_VENDOR_PKT		0xff

static bool reliable_packet(u8_t type)
{
	switch (type) {
	case HCI_COMMAND_PKT:
	case HCI_ACLDATA_PKT:
	case HCI_EVENT_PKT:
		return true;
	default:
		return false;
	}
}

/* FIXME: Correct timeout */
#define H5_RX_ACK_TIMEOUT	K_MSEC(250)
#define H5_TX_ACK_TIMEOUT	K_MSEC(250)

#define SLIP_DELIMITER	0xc0
#define SLIP_ESC	0xdb
#define SLIP_ESC_DELIM	0xdc
#define SLIP_ESC_ESC	0xdd

#define H5_RX_ESC	1
#define H5_TX_ACK_PEND	2

#define H5_HDR_SEQ(hdr)		((hdr)[0] & 0x07)
#define H5_HDR_ACK(hdr)		(((hdr)[0] >> 3) & 0x07)
#define H5_HDR_CRC(hdr)		(((hdr)[0] >> 6) & 0x01)
#define H5_HDR_RELIABLE(hdr)	(((hdr)[0] >> 7) & 0x01)
#define H5_HDR_PKT_TYPE(hdr)	((hdr)[1] & 0x0f)
#define H5_HDR_LEN(hdr)		((((hdr)[1] >> 4) & 0x0f) + ((hdr)[2] << 4))

#define H5_SET_SEQ(hdr, seq)	((hdr)[0] |= (seq))
#define H5_SET_ACK(hdr, ack)	((hdr)[0] |= (ack) << 3)
#define H5_SET_RELIABLE(hdr)	((hdr)[0] |= 1 << 7)
#define H5_SET_TYPE(hdr, type)	((hdr)[1] |= type)
#define H5_SET_LEN(hdr, len)	(((hdr)[1] |= ((len) & 0x0f) << 4), \
				 ((hdr)[2] |= (len) >> 4))

static struct h5 {
	struct net_buf		*rx_buf;

	struct k_fifo		tx_queue;
	struct k_fifo		rx_queue;
	struct k_fifo		unack_queue;

	u8_t			tx_win;
	u8_t			tx_ack;
	u8_t			tx_seq;

	u8_t			rx_ack;

	enum {
		UNINIT,
		INIT,
		ACTIVE,
	}			link_state;

	enum {
		START,
		HEADER,
		PAYLOAD,
		END,
	}			rx_state;
} h5;

static u8_t unack_queue_len;

static const u8_t sync_req[] = { 0x01, 0x7e };
static const u8_t sync_rsp[] = { 0x02, 0x7d };
/* Third byte may change */
static u8_t conf_req[3] = { 0x03, 0xfc };
static const u8_t conf_rsp[] = { 0x04, 0x7b };

/* H5 signal buffers pool */
#define MAX_SIG_LEN	3
#define SIGNAL_COUNT	2
#define SIG_BUF_SIZE (CONFIG_BT_HCI_RESERVE + MAX_SIG_LEN)
NET_BUF_POOL_DEFINE(h5_pool, SIGNAL_COUNT, SIG_BUF_SIZE, 0, NULL);

static struct device *h5_dev;

static void h5_reset_rx(void)
{
	if (h5.rx_buf) {
		net_buf_unref(h5.rx_buf);
		h5.rx_buf = NULL;
	}

	h5.rx_state = START;
}

static int h5_unslip_byte(u8_t *byte)
{
	int count;

	if (*byte != SLIP_ESC) {
		return 0;
	}

	do {
		count = uart_fifo_read(h5_dev, byte, sizeof(*byte));
	} while (!count);

	switch (*byte) {
	case SLIP_ESC_DELIM:
		*byte = SLIP_DELIMITER;
		break;
	case SLIP_ESC_ESC:
		*byte = SLIP_ESC;
		break;
	default:
		BT_ERR("Invalid escape byte %x\n", *byte);
		return -EIO;
	}

	return 0;
}

static void process_unack(void)
{
	u8_t next_seq = h5.tx_seq;
	u8_t number_removed = unack_queue_len;

	if (!unack_queue_len) {
		return;
	}

	BT_DBG("rx_ack %u tx_ack %u tx_seq %u unack_queue_len %u",
	       h5.rx_ack, h5.tx_ack, h5.tx_seq, unack_queue_len);

	while (unack_queue_len > 0) {
		if (next_seq == h5.rx_ack) {
			/* Next sequence number is the same as last received
			 * ack number
			 */
			break;
		}

		number_removed--;
		/* Similar to (n - 1) % 8 with unsigned conversion */
		next_seq = (next_seq - 1) & 0x07;
	}

	if (next_seq != h5.rx_ack) {
		BT_ERR("Wrong sequence: rx_ack %u tx_seq %u next_seq %u",
		       h5.rx_ack, h5.tx_seq, next_seq);
	}

	BT_DBG("Need to remove %u packet from the queue", number_removed);

	while (number_removed) {
		struct net_buf *buf = net_buf_get(&h5.unack_queue, K_NO_WAIT);

		if (!buf) {
			BT_ERR("Unack queue is empty");
			break;
		}

		/* TODO: print or do something with packet */
		BT_DBG("Remove buf from the unack_queue");

		net_buf_unref(buf);
		unack_queue_len--;
		number_removed--;
	}
}

static void h5_print_header(const u8_t *hdr, const char *str)
{
	if (H5_HDR_RELIABLE(hdr)) {
		BT_DBG("%s REL: seq %u ack %u crc %u type %u len %u",
		       str, H5_HDR_SEQ(hdr), H5_HDR_ACK(hdr),
		       H5_HDR_CRC(hdr), H5_HDR_PKT_TYPE(hdr),
		       H5_HDR_LEN(hdr));
	} else {
		BT_DBG("%s UNREL: ack %u crc %u type %u len %u",
		       str, H5_HDR_ACK(hdr), H5_HDR_CRC(hdr),
		       H5_HDR_PKT_TYPE(hdr), H5_HDR_LEN(hdr));
	}
}

#if defined(CONFIG_BT_DEBUG_HCI_DRIVER)
static void hexdump(const char *str, const u8_t *packet, size_t length)
{
	int n = 0;

	if (!length) {
		printk("%s zero-length signal packet\n", str);
		return;
	}

	while (length--) {
		if (n % 16 == 0) {
			printk("%s %08X ", str, n);
		}

		printk("%02X ", *packet++);

		n++;
		if (n % 8 == 0) {
			if (n % 16 == 0) {
				printk("\n");
			} else {
				printk(" ");
			}
		}
	}

	if (n % 16) {
		printk("\n");
	}
}
#else
#define hexdump(str, packet, length)
#endif

static u8_t h5_slip_byte(u8_t byte)
{
	switch (byte) {
	case SLIP_DELIMITER:
		uart_poll_out(h5_dev, SLIP_ESC);
		uart_poll_out(h5_dev, SLIP_ESC_DELIM);
		return 2;
	case SLIP_ESC:
		uart_poll_out(h5_dev, SLIP_ESC);
		uart_poll_out(h5_dev, SLIP_ESC_ESC);
		return 2;
	default:
		uart_poll_out(h5_dev, byte);
		return 1;
	}
}

static void h5_send(const u8_t *payload, u8_t type, int len)
{
	u8_t hdr[4];
	int i;

	hexdump("<= ", payload, len);

	(void)memset(hdr, 0, sizeof(hdr));

	/* Set ACK for outgoing packet and stop delayed work */
	H5_SET_ACK(hdr, h5.tx_ack);
	k_delayed_work_cancel(&ack_work);

	if (reliable_packet(type)) {
		H5_SET_RELIABLE(hdr);
		H5_SET_SEQ(hdr, h5.tx_seq);
		h5.tx_seq = (h5.tx_seq + 1) % 8;
	}

	H5_SET_TYPE(hdr, type);
	H5_SET_LEN(hdr, len);

	/* Calculate CRC */
	hdr[3] = ~((hdr[0] + hdr[1] + hdr[2]) & 0xff);

	h5_print_header(hdr, "TX: <");

	uart_poll_out(h5_dev, SLIP_DELIMITER);

	for (i = 0; i < 4; i++) {
		h5_slip_byte(hdr[i]);
	}

	for (i = 0; i < len; i++) {
		h5_slip_byte(payload[i]);
	}

	uart_poll_out(h5_dev, SLIP_DELIMITER);
}

/* Delayed work taking care about retransmitting packets */
static void retx_timeout(struct k_work *work)
{
	ARG_UNUSED(work);

	BT_DBG("unack_queue_len %u", unack_queue_len);

	if (unack_queue_len) {
		struct k_fifo tmp_queue;
		struct net_buf *buf;

		k_fifo_init(&tmp_queue);

		/* Queue to temperary queue */
		while ((buf = net_buf_get(&h5.tx_queue, K_NO_WAIT))) {
			net_buf_put(&tmp_queue, buf);
		}

		/* Queue unack packets to the beginning of the queue */
		while ((buf = net_buf_get(&h5.unack_queue, K_NO_WAIT))) {
			/* include also packet type */
			net_buf_push(buf, sizeof(u8_t));
			net_buf_put(&h5.tx_queue, buf);
			h5.tx_seq = (h5.tx_seq - 1) & 0x07;
			unack_queue_len--;
		}

		/* Queue saved packets from temp queue */
		while ((buf = net_buf_get(&tmp_queue, K_NO_WAIT))) {
			net_buf_put(&h5.tx_queue, buf);
		}
	}
}

static void ack_timeout(struct k_work *work)
{
	ARG_UNUSED(work);

	BT_DBG("");

	h5_send(NULL, HCI_3WIRE_ACK_PKT, 0);

	/* Analyze stacks */
	STACK_ANALYZE("tx_stack", tx_stack);
	STACK_ANALYZE("rx_stack", rx_stack);
}

static void h5_process_complete_packet(u8_t *hdr)
{
	struct net_buf *buf;

	BT_DBG("");

	/* rx_ack should be in every packet */
	h5.rx_ack = H5_HDR_ACK(hdr);

	if (reliable_packet(H5_HDR_PKT_TYPE(hdr))) {
		/* For reliable packet increment next transmit ack number */
		h5.tx_ack = (h5.tx_ack + 1) % 8;
		/* Submit delayed work to ack the packet */
		k_delayed_work_submit(&ack_work, H5_RX_ACK_TIMEOUT);
	}

	h5_print_header(hdr, "RX: >");

	process_unack();

	buf = h5.rx_buf;
	h5.rx_buf = NULL;

	switch (H5_HDR_PKT_TYPE(hdr)) {
	case HCI_3WIRE_ACK_PKT:
		net_buf_unref(buf);
		break;
	case HCI_3WIRE_LINK_PKT:
		net_buf_put(&h5.rx_queue, buf);
		break;
	case HCI_EVENT_PKT:
	case HCI_ACLDATA_PKT:
		hexdump("=> ", buf->data, buf->len);
		bt_recv(buf);
		break;
	}
}

static inline struct net_buf *get_evt_buf(u8_t evt)
{
	struct net_buf *buf;

	buf = bt_buf_get_evt(evt, false, K_NO_WAIT);
	if (buf) {
		net_buf_add_u8(h5.rx_buf, evt);
	}

	return buf;
}

static void bt_uart_isr(struct device *unused)
{
	static int remaining;
	u8_t byte;
	int ret;
	static u8_t hdr[4];

	ARG_UNUSED(unused);

	while (uart_irq_update(h5_dev) &&
	       uart_irq_is_pending(h5_dev)) {

		if (!uart_irq_rx_ready(h5_dev)) {
			if (uart_irq_tx_ready(h5_dev)) {
				BT_DBG("transmit ready");
			} else {
				BT_DBG("spurious interrupt");
			}
			/* Only the UART RX path is interrupt-enabled */
			break;
		}

		ret = uart_fifo_read(h5_dev, &byte, sizeof(byte));
		if (!ret) {
			continue;
		}

		switch (h5.rx_state) {
		case START:
			if (byte == SLIP_DELIMITER) {
				h5.rx_state = HEADER;
				remaining = sizeof(hdr);
			}
			break;
		case HEADER:
			/* In a case we confuse ending slip delimeter
			 * with starting one.
			 */
			if (byte == SLIP_DELIMITER) {
				remaining = sizeof(hdr);
				continue;
			}

			if (h5_unslip_byte(&byte) < 0) {
				h5_reset_rx();
				continue;
			}

			memcpy(&hdr[sizeof(hdr) - remaining], &byte, 1);
			remaining--;

			if (remaining) {
				break;
			}

			remaining = H5_HDR_LEN(hdr);

			switch (H5_HDR_PKT_TYPE(hdr)) {
			case HCI_EVENT_PKT:
				/* The buffer is allocated only once we know
				 * the exact event type.
				 */
				h5.rx_state = PAYLOAD;
				break;
			case HCI_ACLDATA_PKT:
				h5.rx_buf = bt_buf_get_rx(BT_BUF_ACL_IN,
							  K_NO_WAIT);
				if (!h5.rx_buf) {
					BT_WARN("No available data buffers");
					h5_reset_rx();
					continue;
				}

				h5.rx_state = PAYLOAD;
				break;
			case HCI_3WIRE_LINK_PKT:
			case HCI_3WIRE_ACK_PKT:
				h5.rx_buf = net_buf_alloc(&h5_pool, K_NO_WAIT);
				if (!h5.rx_buf) {
					BT_WARN("No available signal buffers");
					h5_reset_rx();
					continue;
				}

				h5.rx_state = PAYLOAD;
				break;
			default:
				BT_ERR("Wrong packet type %u",
				       H5_HDR_PKT_TYPE(hdr));
				h5.rx_state = END;
				break;
			}
			break;
		case PAYLOAD:
			if (h5_unslip_byte(&byte) < 0) {
				h5_reset_rx();
				continue;
			}

			/* Allocate HCI event buffer now that we know the
			 * exact event type.
			 */
			if (!h5.rx_buf) {
				h5.rx_buf = get_evt_buf(byte);
				if (!h5.rx_buf) {
					BT_WARN("No available event buffers");
					h5_reset_rx();
					continue;
				}
			}

			net_buf_add_mem(h5.rx_buf, &byte, sizeof(byte));
			remaining--;
			if (!remaining) {
				h5.rx_state = END;
			}
			break;
		case END:
			if (byte != SLIP_DELIMITER) {
				BT_ERR("Missing ending SLIP_DELIMITER");
				h5_reset_rx();
				break;
			}

			BT_DBG("Received full packet: type %u",
			       H5_HDR_PKT_TYPE(hdr));

			/* Check when full packet is received, it can be done
			 * when parsing packet header but we need to receive
			 * full packet anyway to clear UART.
			 */
			if (H5_HDR_RELIABLE(hdr) &&
			    H5_HDR_SEQ(hdr) != h5.tx_ack) {
				BT_ERR("Seq expected %u got %u. Drop packet",
				       h5.tx_ack, H5_HDR_SEQ(hdr));
				h5_reset_rx();
				break;
			}

			h5_process_complete_packet(hdr);
			h5.rx_state = START;
			break;
		}
	}
}

static u8_t h5_get_type(struct net_buf *buf)
{
	return net_buf_pull_u8(buf);
}

static int h5_queue(struct net_buf *buf)
{
	u8_t type;

	BT_DBG("buf %p type %u len %u", buf, bt_buf_get_type(buf), buf->len);

	switch (bt_buf_get_type(buf)) {
	case BT_BUF_CMD:
		type = HCI_COMMAND_PKT;
		break;
	case BT_BUF_ACL_OUT:
		type = HCI_ACLDATA_PKT;
		break;
	default:
		BT_ERR("Unknown packet type %u", bt_buf_get_type(buf));
		return -1;
	}

	memcpy(net_buf_push(buf, sizeof(type)), &type, sizeof(type));

	net_buf_put(&h5.tx_queue, buf);

	return 0;
}

static void tx_thread(void)
{
	BT_DBG("");

	/* FIXME: make periodic sending */
	h5_send(sync_req, HCI_3WIRE_LINK_PKT, sizeof(sync_req));

	while (true) {
		struct net_buf *buf;
		u8_t type;

		BT_DBG("link_state %u", h5.link_state);

		switch (h5.link_state) {
		case UNINIT:
			/* FIXME: send sync */
			k_sleep(K_MSEC(100));
			break;
		case INIT:
			/* FIXME: send conf */
			k_sleep(K_MSEC(100));
			break;
		case ACTIVE:
			buf = net_buf_get(&h5.tx_queue, K_FOREVER);
			type = h5_get_type(buf);

			h5_send(buf->data, type, buf->len);

			/* buf is dequeued from tx_queue and queued to unack
			 * queue.
			 */
			net_buf_put(&h5.unack_queue, buf);
			unack_queue_len++;

			k_delayed_work_submit(&retx_work, H5_TX_ACK_TIMEOUT);

			break;
		}
	}
}

static void h5_set_txwin(u8_t *conf)
{
	conf[2] = h5.tx_win & 0x07;
}

static void rx_thread(void)
{
	BT_DBG("");

	while (true) {
		struct net_buf *buf;

		buf = net_buf_get(&h5.rx_queue, K_FOREVER);

		hexdump("=> ", buf->data, buf->len);

		if (!memcmp(buf->data, sync_req, sizeof(sync_req))) {
			if (h5.link_state == ACTIVE) {
				/* TODO Reset H5 */
			}

			h5_send(sync_rsp, HCI_3WIRE_LINK_PKT, sizeof(sync_rsp));
		} else if (!memcmp(buf->data, sync_rsp, sizeof(sync_rsp))) {
			if (h5.link_state == ACTIVE) {
				/* TODO Reset H5 */
			}

			h5.link_state = INIT;
			h5_set_txwin(conf_req);
			h5_send(conf_req, HCI_3WIRE_LINK_PKT, sizeof(conf_req));
		} else if (!memcmp(buf->data, conf_req, 2)) {
			/*
			 * The Host sends Config Response messages without a
			 * Configuration Field.
			 */
			h5_send(conf_rsp, HCI_3WIRE_LINK_PKT, sizeof(conf_rsp));

			/* Then send Config Request with Configuration Field */
			h5_set_txwin(conf_req);
			h5_send(conf_req, HCI_3WIRE_LINK_PKT, sizeof(conf_req));
		} else if (!memcmp(buf->data, conf_rsp, 2)) {
			h5.link_state = ACTIVE;
			if (buf->len > 2) {
				/* Configuration field present */
				h5.tx_win = (buf->data[2] & 0x07);
			}

			BT_DBG("Finished H5 configuration, tx_win %u",
			       h5.tx_win);
		} else {
			BT_ERR("Not handled yet %x %x",
			       buf->data[0], buf->data[1]);
		}

		net_buf_unref(buf);

		/* Make sure we don't hog the CPU if the rx_queue never
		 * gets empty.
		 */
		k_yield();
	}
}

static void h5_init(void)
{
	BT_DBG("");

	h5.link_state = UNINIT;
	h5.rx_state = START;
	h5.tx_win = 4U;

	/* TX thread */
	k_fifo_init(&h5.tx_queue);
	k_thread_create(&tx_thread_data, tx_stack,
			K_THREAD_STACK_SIZEOF(tx_stack),
			(k_thread_entry_t)tx_thread, NULL, NULL, NULL,
			K_PRIO_COOP(CONFIG_BT_HCI_TX_PRIO),
			0, K_NO_WAIT);

	k_fifo_init(&h5.rx_queue);
	k_thread_create(&rx_thread_data, rx_stack,
			K_THREAD_STACK_SIZEOF(rx_stack),
			(k_thread_entry_t)rx_thread, NULL, NULL, NULL,
			K_PRIO_COOP(CONFIG_BT_RX_PRIO),
			0, K_NO_WAIT);

	/* Unack queue */
	k_fifo_init(&h5.unack_queue);

	/* Init delayed work */
	k_delayed_work_init(&ack_work, ack_timeout);
	k_delayed_work_init(&retx_work, retx_timeout);
}

static int h5_open(void)
{
	BT_DBG("");

	uart_irq_rx_disable(h5_dev);
	uart_irq_tx_disable(h5_dev);

	bt_uart_drain(h5_dev);

	uart_irq_callback_set(h5_dev, bt_uart_isr);

	h5_init();

	uart_irq_rx_enable(h5_dev);

	return 0;
}

static const struct bt_hci_driver drv = {
	.name		= "H:5",
	.bus		= BT_HCI_DRIVER_BUS_UART,
	.open		= h5_open,
	.send		= h5_queue,
};

static int bt_uart_init(struct device *unused)
{
	ARG_UNUSED(unused);

	h5_dev = device_get_binding(CONFIG_BT_UART_ON_DEV_NAME);

	if (h5_dev == NULL) {
		return -EINVAL;
	}

	bt_hci_driver_register(&drv);

	return 0;
}

SYS_INIT(bt_uart_init, POST_KERNEL, CONFIG_KERNEL_INIT_PRIORITY_DEVICE);