/*
 * Intel MIC Platform Software Stack (MPSS)
 *
 * Copyright(c) 2015 Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as
 * published by the Free Software Foundation.
 *
 * 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.
 *
 * The full GNU General Public License is included in this distribution in
 * the file called "COPYING".
 *
 * Intel MIC COSM Client Driver
 *
 */
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/reboot.h>
#include <linux/kthread.h>
#include <linux/sched/signal.h>

#include "../cosm/cosm_main.h"

#define COSM_SCIF_MAX_RETRIES 10
#define COSM_HEARTBEAT_SEND_MSEC (COSM_HEARTBEAT_SEND_SEC * MSEC_PER_SEC)

static struct task_struct *client_thread;
static scif_epd_t client_epd;
static struct scif_peer_dev *client_spdev;

/*
 * Reboot notifier: receives shutdown status from the OS and communicates it
 * back to the COSM process on the host
 */
static int cosm_reboot_event(struct notifier_block *this, unsigned long event,
			     void *ptr)
{
	struct cosm_msg msg = { .id = COSM_MSG_SHUTDOWN_STATUS };
	int rc;

	event = (event == SYS_RESTART) ? SYSTEM_RESTART : event;
	dev_info(&client_spdev->dev, "%s %d received event %ld\n",
		 __func__, __LINE__, event);

	msg.shutdown_status = event;
	rc = scif_send(client_epd, &msg, sizeof(msg), SCIF_SEND_BLOCK);
	if (rc < 0)
		dev_err(&client_spdev->dev, "%s %d scif_send rc %d\n",
			__func__, __LINE__, rc);

	return NOTIFY_DONE;
}

static struct notifier_block cosm_reboot = {
	.notifier_call  = cosm_reboot_event,
};

/* Set system time from timespec value received from the host */
static void cosm_set_time(struct cosm_msg *msg)
{
	struct timespec64 ts = {
		.tv_sec = msg->timespec.tv_sec,
		.tv_nsec = msg->timespec.tv_nsec,
	};
	int rc = do_settimeofday64(&ts);

	if (rc)
		dev_err(&client_spdev->dev, "%s: %d settimeofday rc %d\n",
			__func__, __LINE__, rc);
}

/* COSM client receive message processing */
static void cosm_client_recv(void)
{
	struct cosm_msg msg;
	int rc;

	while (1) {
		rc = scif_recv(client_epd, &msg, sizeof(msg), 0);
		if (!rc) {
			return;
		} else if (rc < 0) {
			dev_err(&client_spdev->dev, "%s: %d rc %d\n",
				__func__, __LINE__, rc);
			return;
		}

		dev_dbg(&client_spdev->dev, "%s: %d rc %d id 0x%llx\n",
			__func__, __LINE__, rc, msg.id);

		switch (msg.id) {
		case COSM_MSG_SYNC_TIME:
			cosm_set_time(&msg);
			break;
		case COSM_MSG_SHUTDOWN:
			orderly_poweroff(true);
			break;
		default:
			dev_err(&client_spdev->dev, "%s: %d unknown id %lld\n",
				__func__, __LINE__, msg.id);
			break;
		}
	}
}

/* Initiate connection to the COSM server on the host */
static int cosm_scif_connect(void)
{
	struct scif_port_id port_id;
	int i, rc;

	client_epd = scif_open();
	if (!client_epd) {
		dev_err(&client_spdev->dev, "%s %d scif_open failed\n",
			__func__, __LINE__);
		return -ENOMEM;
	}

	port_id.node = 0;
	port_id.port = SCIF_COSM_LISTEN_PORT;

	for (i = 0; i < COSM_SCIF_MAX_RETRIES; i++) {
		rc = scif_connect(client_epd, &port_id);
		if (rc < 0)
			msleep(1000);
		else
			break;
	}

	if (rc < 0) {
		dev_err(&client_spdev->dev, "%s %d scif_connect rc %d\n",
			__func__, __LINE__, rc);
		scif_close(client_epd);
		client_epd = NULL;
	}
	return rc < 0 ? rc : 0;
}

/* Close host SCIF connection */
static void cosm_scif_connect_exit(void)
{
	if (client_epd) {
		scif_close(client_epd);
		client_epd = NULL;
	}
}

/*
 * COSM SCIF client thread function: waits for messages from the host and sends
 * a heartbeat to the host
 */
static int cosm_scif_client(void *unused)
{
	struct cosm_msg msg = { .id = COSM_MSG_HEARTBEAT };
	struct scif_pollepd pollepd;
	int rc;

	allow_signal(SIGKILL);

	while (!kthread_should_stop()) {
		pollepd.epd = client_epd;
		pollepd.events = EPOLLIN;

		rc = scif_poll(&pollepd, 1, COSM_HEARTBEAT_SEND_MSEC);
		if (rc < 0) {
			if (-EINTR != rc)
				dev_err(&client_spdev->dev,
					"%s %d scif_poll rc %d\n",
					__func__, __LINE__, rc);
			continue;
		}

		if (pollepd.revents & EPOLLIN)
			cosm_client_recv();

		msg.id = COSM_MSG_HEARTBEAT;
		rc = scif_send(client_epd, &msg, sizeof(msg), SCIF_SEND_BLOCK);
		if (rc < 0)
			dev_err(&client_spdev->dev, "%s %d scif_send rc %d\n",
				__func__, __LINE__, rc);
	}

	dev_dbg(&client_spdev->dev, "%s %d Client thread stopped\n",
		__func__, __LINE__);
	return 0;
}

static void cosm_scif_probe(struct scif_peer_dev *spdev)
{
	int rc;

	dev_dbg(&spdev->dev, "%s %d: dnode %d\n",
		__func__, __LINE__, spdev->dnode);

	/* We are only interested in the host with spdev->dnode == 0 */
	if (spdev->dnode)
		return;

	client_spdev = spdev;
	rc = cosm_scif_connect();
	if (rc)
		goto exit;

	rc = register_reboot_notifier(&cosm_reboot);
	if (rc) {
		dev_err(&spdev->dev,
			"reboot notifier registration failed rc %d\n", rc);
		goto connect_exit;
	}

	client_thread = kthread_run(cosm_scif_client, NULL, "cosm_client");
	if (IS_ERR(client_thread)) {
		rc = PTR_ERR(client_thread);
		dev_err(&spdev->dev, "%s %d kthread_run rc %d\n",
			__func__, __LINE__, rc);
		goto unreg_reboot;
	}
	return;
unreg_reboot:
	unregister_reboot_notifier(&cosm_reboot);
connect_exit:
	cosm_scif_connect_exit();
exit:
	client_spdev = NULL;
}

static void cosm_scif_remove(struct scif_peer_dev *spdev)
{
	int rc;

	dev_dbg(&spdev->dev, "%s %d: dnode %d\n",
		__func__, __LINE__, spdev->dnode);

	if (spdev->dnode)
		return;

	if (!IS_ERR_OR_NULL(client_thread)) {
		rc = send_sig(SIGKILL, client_thread, 0);
		if (rc) {
			pr_err("%s %d send_sig rc %d\n",
			       __func__, __LINE__, rc);
			return;
		}
		kthread_stop(client_thread);
	}
	unregister_reboot_notifier(&cosm_reboot);
	cosm_scif_connect_exit();
	client_spdev = NULL;
}

static struct scif_client scif_client_cosm = {
	.name = KBUILD_MODNAME,
	.probe = cosm_scif_probe,
	.remove = cosm_scif_remove,
};

static int __init cosm_client_init(void)
{
	int rc = scif_client_register(&scif_client_cosm);

	if (rc)
		pr_err("scif_client_register failed rc %d\n", rc);
	return rc;
}

static void __exit cosm_client_exit(void)
{
	scif_client_unregister(&scif_client_cosm);
}

module_init(cosm_client_init);
module_exit(cosm_client_exit);

MODULE_AUTHOR("Intel Corporation");
MODULE_DESCRIPTION("Intel(R) MIC card OS state management client driver");
MODULE_LICENSE("GPL v2");
