/* Copyright 2013-2014 IBM Corp.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * 	http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <skiboot.h>
#include <lpc.h>
#include <lock.h>
#include <device.h>
#include <timebase.h>
#include <ipmi.h>
#include <bt.h>
#include <timer.h>

/* BT registers */
#define BT_CTRL			0
#define   BT_CTRL_B_BUSY		0x80
#define   BT_CTRL_H_BUSY		0x40
#define   BT_CTRL_OEM0			0x20
#define   BT_CTRL_SMS_ATN		0x10
#define   BT_CTRL_B2H_ATN		0x08
#define   BT_CTRL_H2B_ATN		0x04
#define   BT_CTRL_CLR_RD_PTR		0x02
#define   BT_CTRL_CLR_WR_PTR		0x01
#define BT_HOST2BMC		1
#define BT_INTMASK		2
#define   BT_INTMASK_B2H_IRQEN		0x01
#define   BT_INTMASK_B2H_IRQ		0x02
#define   BT_INTMASK_BMC_HWRST		0x80

/* Default poll interval before interrupts are working */
#define BT_DEFAULT_POLL_MS	200

/*
 * Minimum size of an IPMI request/response including
 * mandatory headers.
 */
#define BT_MIN_REQ_LEN 3
#define BT_MIN_RESP_LEN 4

/*
 * How long (in uS) to poll for new ipmi data.
 */
#define POLL_TIMEOUT 10000

/*
 * Maximum number of outstanding messages to allow in the queue.
 */
#define BT_MAX_QUEUE_LEN 10

/*
 * How long (in TB ticks) before a message is timed out.
 */
#define BT_MSG_TIMEOUT (secs_to_tb(3))

/*
 * Maximum number of times to attempt sending a message before giving up.
 */
#define BT_MAX_RETRY_COUNT 1

#define BT_QUEUE_DEBUG 0

#define BT_ERR(msg, fmt, args...) \
	do { prerror("BT seq 0x%02x netfn 0x%02x cmd 0x%02x: " fmt "\n", \
	     (msg)->seq, (msg)->ipmi_msg.netfn, (msg)->ipmi_msg.cmd, ##args); \
	} while(0)

enum bt_states {
	BT_STATE_IDLE = 0,
	BT_STATE_RESP_WAIT,
};

struct bt_msg {
	struct list_node link;
	unsigned long tb;
	uint8_t seq;
	uint8_t retry_count;
	struct ipmi_msg ipmi_msg;
};

struct bt {
	uint32_t base_addr;
	enum bt_states state;
	struct lock lock;
	struct list_head msgq;
	struct timer poller;
	bool irq_ok;
	int queue_len;
};
static struct bt bt;

static int ipmi_seq;

static inline uint8_t bt_inb(uint32_t reg)
{
	return lpc_inb(bt.base_addr + reg);
}

static inline void bt_outb(uint8_t data, uint32_t reg)
{
	lpc_outb(data, bt.base_addr + reg);
}

static inline void bt_set_h_busy(bool value)
{
	uint8_t rval;

	rval = bt_inb(BT_CTRL);
	if (value != !!(rval & BT_CTRL_H_BUSY))
		bt_outb(BT_CTRL_H_BUSY, BT_CTRL);
}

static inline bool bt_idle(void)
{
	uint8_t bt_ctrl = bt_inb(BT_CTRL);

	return !(bt_ctrl & BT_CTRL_B_BUSY) && !(bt_ctrl & BT_CTRL_H2B_ATN);
}

static inline void bt_set_state(enum bt_states next_state)
{
	bt.state = next_state;
}

/* Must be called with bt.lock held */
static void bt_msg_del(struct bt_msg *bt_msg)
{
	list_del(&bt_msg->link);
	bt.queue_len--;
	unlock(&bt.lock);
	ipmi_cmd_done(bt_msg->ipmi_msg.cmd, bt_msg->ipmi_msg.netfn + (1 << 2),
		      IPMI_TIMEOUT_ERR, &bt_msg->ipmi_msg);
	lock(&bt.lock);
}

static void bt_init_interface(void)
{
	/* Clear interrupt condition & enable irq */
	bt_outb(BT_INTMASK_B2H_IRQ | BT_INTMASK_B2H_IRQEN, BT_INTMASK);

	/* Take care of a stable H_BUSY if any */
	bt_set_h_busy(false);

	bt_set_state(BT_STATE_IDLE);
}

static void bt_reset_interface(void)
{
	bt_outb(BT_INTMASK_BMC_HWRST, BT_INTMASK);
	bt_init_interface();
}

/* Try and send a message from the message queue. Caller must hold
 * bt.bt_lock and bt.lock and ensue the message queue is not
 * empty. */
static void bt_send_msg(void)
{
	int i;
	struct bt_msg *bt_msg;
	struct ipmi_msg *ipmi_msg;

	bt_msg = list_top(&bt.msgq, struct bt_msg, link);
	assert(bt_msg);

	ipmi_msg = &bt_msg->ipmi_msg;

	/* Send the message */
	bt_outb(BT_CTRL_CLR_WR_PTR, BT_CTRL);

	/* Byte 1 - Length */
	bt_outb(ipmi_msg->req_size + BT_MIN_REQ_LEN, BT_HOST2BMC);

	/* Byte 2 - NetFn/LUN */
	bt_outb(ipmi_msg->netfn, BT_HOST2BMC);

	/* Byte 3 - Seq */
	bt_outb(bt_msg->seq, BT_HOST2BMC);

	/* Byte 4 - Cmd */
	bt_outb(ipmi_msg->cmd, BT_HOST2BMC);

	/* Byte 5:N - Data */
	for (i = 0; i < ipmi_msg->req_size; i++)
		bt_outb(ipmi_msg->data[i], BT_HOST2BMC);

	bt_msg->tb = mftb();
	bt_outb(BT_CTRL_H2B_ATN, BT_CTRL);
	bt_set_state(BT_STATE_RESP_WAIT);

	return;
}

static void bt_flush_msg(void)
{
	bt_outb(BT_CTRL_B2H_ATN | BT_CTRL_CLR_RD_PTR, BT_CTRL);
	bt_set_h_busy(false);
}

static void bt_get_resp(void)
{
	int i;
	struct bt_msg *tmp_bt_msg, *bt_msg = NULL;
	struct ipmi_msg *ipmi_msg;
	uint8_t resp_len, netfn, seq, cmd;
	uint8_t cc = IPMI_CC_NO_ERROR;

	/* Indicate to the BMC that we are busy */
	bt_set_h_busy(true);

	/* Clear B2H_ATN and read pointer */
	bt_outb(BT_CTRL_B2H_ATN, BT_CTRL);
	bt_outb(BT_CTRL_CLR_RD_PTR, BT_CTRL);

	/* Read the response */
	/* Byte 1 - Length (includes header size) */
	resp_len = bt_inb(BT_HOST2BMC) - BT_MIN_RESP_LEN;

	/* Byte 2 - NetFn/LUN */
	netfn = bt_inb(BT_HOST2BMC);

	/* Byte 3 - Seq */
	seq = bt_inb(BT_HOST2BMC);

	/* Byte 4 - Cmd */
	cmd = bt_inb(BT_HOST2BMC);

	/* Byte 5 - Completion Code */
	cc = bt_inb(BT_HOST2BMC);

	/* Find the corresponding messasge */
	list_for_each(&bt.msgq, tmp_bt_msg, link) {
		if (tmp_bt_msg->seq == seq) {
			bt_msg = tmp_bt_msg;
			break;
		}

	}
	if (!bt_msg) {
		/* A response to a message we no longer care about. */
		prlog(PR_INFO, "BT: Nobody cared about a response to an BT/IPMI message\n");
		bt_flush_msg();
		bt_set_state(BT_STATE_IDLE);
		return;
	}

	ipmi_msg = &bt_msg->ipmi_msg;

	/*
	 * Make sure we have enough room to store the resposne. As all values
	 * are unsigned we will also trigger this error if
	 * bt_inb(BT_HOST2BMC) < BT_MIN_RESP_LEN (which should never occur).
	 */
	if (resp_len > ipmi_msg->resp_size) {
		BT_ERR(bt_msg, "Invalid resp_len %d", resp_len);
		resp_len = ipmi_msg->resp_size;
		cc = IPMI_ERR_MSG_TRUNCATED;
	}
	ipmi_msg->resp_size = resp_len;

	/* Byte 6:N - Data */
	for (i = 0; i < resp_len; i++)
		ipmi_msg->data[i] = bt_inb(BT_HOST2BMC);
	bt_set_h_busy(false);

	bt_set_state(BT_STATE_IDLE);

	list_del(&bt_msg->link);
	bt.queue_len--;
	unlock(&bt.lock);

	/*
	 * Call the IPMI layer to finish processing the message.
	 */
#if BT_QUEUE_DEBUG
	prlog(PR_DEBUG, "cmd 0x%02x done\n", seq);
#endif

	ipmi_cmd_done(cmd, netfn, cc, ipmi_msg);
	lock(&bt.lock);

	return;
}

static void bt_expire_old_msg(void)
{
	unsigned long tb;
	struct bt_msg *bt_msg;

	tb = mftb();
	bt_msg = list_top(&bt.msgq, struct bt_msg, link);

	if (bt_msg && bt_msg->tb > 0 && (bt_msg->tb + BT_MSG_TIMEOUT) < tb) {
		if (bt_msg->retry_count < BT_MAX_RETRY_COUNT) {
			/* A message timeout is usually due to the BMC
			clearing the H2B_ATN flag without actually
			doing anything. The data will still be in the
			FIFO so just reset the flag.*/
			BT_ERR(bt_msg, "Retry sending message");
			bt_msg->retry_count++;
			bt_msg->tb = mftb();
			bt_outb(BT_CTRL_H2B_ATN, BT_CTRL);
		} else {
			BT_ERR(bt_msg, "Timeout sending message");
			bt_msg_del(bt_msg);

			/* Timing out a message is inherently racy as the BMC
			   may start writing just as we decide to kill the
			   message. Hopefully resetting the interface is
			   sufficient to guard against such things. */
			bt_reset_interface();
		}
	}
}

#if BT_QUEUE_DEBUG
static void print_debug_queue_info(void)
{
	struct bt_msg *msg;
	static bool printed = false;

	if (!list_empty(&bt.msgq)) {
		printed = false;
		prlog(PR_DEBUG, "-------- BT Msg Queue --------\n");
		list_for_each(&bt.msgq, msg, link) {
			prlog(PR_DEBUG, "Seq: 0x%02x Cmd: 0x%02x\n", msg->seq, msg->ipmi_msg.cmd);
		}
		prlog(PR_DEBUG, "-----------------------------\n");
	} else if (!printed) {
		printed = true;
		prlog(PR_DEBUG, "----- BT Msg Queue Empty -----\n");
	}
}
#else
static void print_debug_queue_info(void) {}
#endif

static void bt_send_and_unlock(void)
{
	if (lpc_ok() && bt_idle() && !list_empty(&bt.msgq)
	    && bt.state == BT_STATE_IDLE)
		bt_send_msg();

	unlock(&bt.lock);
	return;
}

static void bt_poll(struct timer *t __unused, void *data __unused)
{
	uint8_t bt_ctrl;

	/* Don't do anything if the LPC bus is offline */
	if (!lpc_ok())
		return;

	/* If we can't get the lock assume someone else will notice
	 * the new message and process it. */
	lock(&bt.lock);

	print_debug_queue_info();
	bt_expire_old_msg();

	bt_ctrl = bt_inb(BT_CTRL);

	/* Is there a response waiting for us? */
	if (bt.state == BT_STATE_RESP_WAIT &&
	    (bt_ctrl & BT_CTRL_B2H_ATN))
		bt_get_resp();

	/* Check for sms_atn */
	if (bt_inb(BT_CTRL) & BT_CTRL_SMS_ATN) {
		bt_outb(BT_CTRL_SMS_ATN, BT_CTRL);
		unlock(&bt.lock);
		ipmi_sms_attention();
		lock(&bt.lock);
	}

	/* Send messages if we can. If the BMC was really quick we
	   could loop back to the start and check for a response
	   instead of unlocking, but testing shows the BMC isn't that
	   fast so we will wait for the IRQ or a call to the pollers
	   instead. */
	bt_send_and_unlock();

	schedule_timer(&bt.poller,
		       bt.irq_ok ? TIMER_POLL : msecs_to_tb(BT_DEFAULT_POLL_MS));
}

static void bt_add_msg(struct bt_msg *bt_msg)
{
	bt_msg->tb = 0;
	bt_msg->seq = ipmi_seq++;
	bt_msg->retry_count = 0;
	bt.queue_len++;
	if (bt.queue_len > BT_MAX_QUEUE_LEN) {
		/* Maximum queue length exceeded - remove the oldest message
		   from the queue. */
		BT_ERR(bt_msg, "Maximum queue length exceeded");
		bt_msg = list_tail(&bt.msgq, struct bt_msg, link);
		assert(bt_msg);
		BT_ERR(bt_msg, "Removed from queue");
		bt_msg_del(bt_msg);
	}
}

static int bt_add_ipmi_msg_head(struct ipmi_msg *ipmi_msg)
{
	struct bt_msg *bt_msg = container_of(ipmi_msg, struct bt_msg, ipmi_msg);

	lock(&bt.lock);
	bt_add_msg(bt_msg);
	list_add(&bt.msgq, &bt_msg->link);
	bt_send_and_unlock();

	return 0;
}

static int bt_add_ipmi_msg(struct ipmi_msg *ipmi_msg)
{
	struct bt_msg *bt_msg = container_of(ipmi_msg, struct bt_msg, ipmi_msg);

	lock(&bt.lock);
	bt_add_msg(bt_msg);
	list_add_tail(&bt.msgq, &bt_msg->link);
	bt_send_and_unlock();

	return 0;
}

static void bt_irq(uint32_t chip_id __unused, uint32_t irq_mask __unused)
{
	uint8_t ireg;

	ireg = bt_inb(BT_INTMASK);

	bt.irq_ok = true;
	if (ireg & BT_INTMASK_B2H_IRQ) {
		bt_outb(BT_INTMASK_B2H_IRQ | BT_INTMASK_B2H_IRQEN, BT_INTMASK);
		bt_poll(NULL, NULL);
	}
}

/*
 * Allocate an ipmi message and bt container and return the ipmi
 * message struct. Allocates enough space for the request and response
 * data.
 */
static struct ipmi_msg *bt_alloc_ipmi_msg(size_t request_size, size_t response_size)
{
	struct bt_msg *bt_msg;

	bt_msg = zalloc(sizeof(struct bt_msg) + MAX(request_size, response_size));
	if (!bt_msg)
		return NULL;

	bt_msg->ipmi_msg.req_size = request_size;
	bt_msg->ipmi_msg.resp_size = response_size;
	bt_msg->ipmi_msg.data = (uint8_t *) (bt_msg + 1);

	return &bt_msg->ipmi_msg;
}

/*
 * Free a previously allocated ipmi message.
 */
static void bt_free_ipmi_msg(struct ipmi_msg *ipmi_msg)
{
	struct bt_msg *bt_msg = container_of(ipmi_msg, struct bt_msg, ipmi_msg);

	free(bt_msg);
}

/*
 * Remove a message from the queue. The memory allocated for the ipmi message
 * will need to be freed by the caller with bt_free_ipmi_msg() as it will no
 * longer be in the queue of messages.
 */
static int bt_del_ipmi_msg(struct ipmi_msg *ipmi_msg)
{
	struct bt_msg *bt_msg = container_of(ipmi_msg, struct bt_msg, ipmi_msg);

	lock(&bt.lock);
	list_del(&bt_msg->link);
	bt.queue_len--;
	bt_send_and_unlock();
	return 0;
}

static struct ipmi_backend bt_backend = {
	.alloc_msg = bt_alloc_ipmi_msg,
	.free_msg = bt_free_ipmi_msg,
	.queue_msg = bt_add_ipmi_msg,
	.queue_msg_head = bt_add_ipmi_msg_head,
	.dequeue_msg = bt_del_ipmi_msg,
};

static struct lpc_client bt_lpc_client = {
	.interrupt = bt_irq,
};

void bt_init(void)
{
	struct dt_node *n;
	const struct dt_property *prop;
	uint32_t irq;

	/* We support only one */
	n = dt_find_compatible_node(dt_root, NULL, "ipmi-bt");
	if (!n)
		return;

	/* Get IO base */
	prop = dt_find_property(n, "reg");
	if (!prop) {
		prerror("BT: Can't find reg property\n");
		return;
	}
	if (dt_property_get_cell(prop, 0) != OPAL_LPC_IO) {
		prerror("BT: Only supports IO addresses\n");
		return;
	}
	bt.base_addr = dt_property_get_cell(prop, 1);
	init_timer(&bt.poller, bt_poll, NULL);

	bt_init_interface();
	init_lock(&bt.lock);

	/*
	 * The iBT interface comes up in the busy state until the daemon has
	 * initialised it.
	 */
	bt_set_state(BT_STATE_IDLE);
	list_head_init(&bt.msgq);
	bt.queue_len = 0;

	printf("BT: Interface intialized, IO 0x%04x\n", bt.base_addr);

	ipmi_register_backend(&bt_backend);

	/* We initially schedule the poller as a relatively fast timer, at
	 * least until we have at least one interrupt occurring at which
	 * point we turn it into a background poller
	 */
	schedule_timer(&bt.poller, msecs_to_tb(BT_DEFAULT_POLL_MS));

	irq = dt_prop_get_u32(n, "interrupts");
	bt_lpc_client.interrupts = LPC_IRQ(irq);
	lpc_register_client(dt_get_chip_id(n), &bt_lpc_client);
	prlog(PR_DEBUG, "BT: Using LPC IRQ %d\n", irq);
}