// SPDX-License-Identifier: GPL-2.0
/*
 * USB Typec-C Thunderbolt3 Alternate Mode driver
 *
 * Copyright (C) 2019 Intel Corporation
 * Author: Heikki Krogerus <heikki.krogerus@linux.intel.com>
 */

#include <linux/lockdep.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/workqueue.h>
#include <linux/usb/pd_vdo.h>
#include <linux/usb/typec_altmode.h>
#include <linux/usb/typec_tbt.h>

enum tbt_state {
	TBT_STATE_IDLE,
	TBT_STATE_SOP_P_ENTER,
	TBT_STATE_SOP_PP_ENTER,
	TBT_STATE_ENTER,
	TBT_STATE_EXIT,
	TBT_STATE_SOP_PP_EXIT,
	TBT_STATE_SOP_P_EXIT
};

struct tbt_altmode {
	enum tbt_state state;
	struct typec_cable *cable;
	struct typec_altmode *alt;
	struct typec_altmode *plug[2];
	u32 enter_vdo;

	struct work_struct work;
	struct mutex lock; /* device lock */
};

static bool tbt_ready(struct typec_altmode *alt);

static int tbt_enter_mode(struct tbt_altmode *tbt)
{
	struct typec_altmode *plug = tbt->plug[TYPEC_PLUG_SOP_P];
	u32 vdo;

	vdo = tbt->alt->vdo & (TBT_VENDOR_SPECIFIC_B0 | TBT_VENDOR_SPECIFIC_B1);
	vdo |= tbt->alt->vdo & TBT_INTEL_SPECIFIC_B0;
	vdo |= TBT_MODE;

	if (plug) {
		if (typec_cable_is_active(tbt->cable))
			vdo |= TBT_ENTER_MODE_ACTIVE_CABLE;

		vdo |= TBT_ENTER_MODE_CABLE_SPEED(TBT_CABLE_SPEED(plug->vdo));
		vdo |= plug->vdo & TBT_CABLE_ROUNDED;
		vdo |= plug->vdo & TBT_CABLE_OPTICAL;
		vdo |= plug->vdo & TBT_CABLE_RETIMER;
		vdo |= plug->vdo & TBT_CABLE_LINK_TRAINING;
	} else {
		vdo |= TBT_ENTER_MODE_CABLE_SPEED(TBT_CABLE_USB3_PASSIVE);
	}

	tbt->enter_vdo = vdo;
	return typec_altmode_enter(tbt->alt, &vdo);
}

static void tbt_altmode_work(struct work_struct *work)
{
	struct tbt_altmode *tbt = container_of(work, struct tbt_altmode, work);
	int ret;

	mutex_lock(&tbt->lock);

	switch (tbt->state) {
	case TBT_STATE_SOP_P_ENTER:
		ret = typec_cable_altmode_enter(tbt->alt, TYPEC_PLUG_SOP_P, NULL);
		if (ret) {
			dev_dbg(&tbt->plug[TYPEC_PLUG_SOP_P]->dev,
				"failed to enter mode (%d)\n", ret);
			goto disable_plugs;
		}
		break;
	case TBT_STATE_SOP_PP_ENTER:
		ret = typec_cable_altmode_enter(tbt->alt, TYPEC_PLUG_SOP_PP,  NULL);
		if (ret) {
			dev_dbg(&tbt->plug[TYPEC_PLUG_SOP_PP]->dev,
				"failed to enter mode (%d)\n", ret);
			goto disable_plugs;
		}
		break;
	case TBT_STATE_ENTER:
		ret = tbt_enter_mode(tbt);
		if (ret)
			dev_dbg(&tbt->alt->dev, "failed to enter mode (%d)\n",
				ret);
		break;
	case TBT_STATE_EXIT:
		typec_altmode_exit(tbt->alt);
		break;
	case TBT_STATE_SOP_PP_EXIT:
		typec_cable_altmode_exit(tbt->alt, TYPEC_PLUG_SOP_PP);
		break;
	case TBT_STATE_SOP_P_EXIT:
		typec_cable_altmode_exit(tbt->alt, TYPEC_PLUG_SOP_P);
		break;
	default:
		break;
	}

	tbt->state = TBT_STATE_IDLE;

	mutex_unlock(&tbt->lock);
	return;

disable_plugs:
	for (int i = TYPEC_PLUG_SOP_PP; i >= 0; --i) {
		if (tbt->plug[i])
			typec_altmode_put_plug(tbt->plug[i]);

		tbt->plug[i] = NULL;
	}

	tbt->state = TBT_STATE_ENTER;
	schedule_work(&tbt->work);
	mutex_unlock(&tbt->lock);
}

/*
 * If SOP' is available, enter that first (which will trigger a VDM response
 * that will enter SOP" if available and then the port). If entering SOP' fails,
 * stop attempting to enter either cable altmode (probably not supported) and
 * directly enter the port altmode.
 */
static int tbt_enter_modes_ordered(struct typec_altmode *alt)
{
	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
	int ret = 0;

	lockdep_assert_held(&tbt->lock);

	if (!tbt_ready(tbt->alt))
		return -ENODEV;

	if (tbt->plug[TYPEC_PLUG_SOP_P]) {
		ret = typec_cable_altmode_enter(alt, TYPEC_PLUG_SOP_P, NULL);
		if (ret < 0) {
			for (int i = TYPEC_PLUG_SOP_PP; i >= 0; --i) {
				if (tbt->plug[i])
					typec_altmode_put_plug(tbt->plug[i]);

				tbt->plug[i] = NULL;
			}
		} else {
			return ret;
		}
	}

	return tbt_enter_mode(tbt);
}

static int tbt_cable_altmode_vdm(struct typec_altmode *alt,
				 enum typec_plug_index sop, const u32 hdr,
				 const u32 *vdo, int count)
{
	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
	int cmd_type = PD_VDO_CMDT(hdr);
	int cmd = PD_VDO_CMD(hdr);

	mutex_lock(&tbt->lock);

	if (tbt->state != TBT_STATE_IDLE) {
		mutex_unlock(&tbt->lock);
		return -EBUSY;
	}

	switch (cmd_type) {
	case CMDT_RSP_ACK:
		switch (cmd) {
		case CMD_ENTER_MODE:
			/*
			 * Following the order described in USB Type-C Spec
			 * R2.0 Section 6.7.3: SOP', SOP", then port.
			 */
			if (sop == TYPEC_PLUG_SOP_P) {
				if (tbt->plug[TYPEC_PLUG_SOP_PP])
					tbt->state = TBT_STATE_SOP_PP_ENTER;
				else
					tbt->state = TBT_STATE_ENTER;
			} else if (sop == TYPEC_PLUG_SOP_PP)
				tbt->state = TBT_STATE_ENTER;

			break;
		case CMD_EXIT_MODE:
			/* Exit in opposite order: Port, SOP", then SOP'. */
			if (sop == TYPEC_PLUG_SOP_PP)
				tbt->state = TBT_STATE_SOP_P_EXIT;
			break;
		}
		break;
	default:
		break;
	}

	if (tbt->state != TBT_STATE_IDLE)
		schedule_work(&tbt->work);

	mutex_unlock(&tbt->lock);
	return 0;
}

static int tbt_altmode_vdm(struct typec_altmode *alt,
			   const u32 hdr, const u32 *vdo, int count)
{
	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
	struct typec_thunderbolt_data data;
	int cmd_type = PD_VDO_CMDT(hdr);
	int cmd = PD_VDO_CMD(hdr);

	mutex_lock(&tbt->lock);

	if (tbt->state != TBT_STATE_IDLE) {
		mutex_unlock(&tbt->lock);
		return -EBUSY;
	}

	switch (cmd_type) {
	case CMDT_RSP_ACK:
		/* Port altmode is last to enter and first to exit. */
		switch (cmd) {
		case CMD_ENTER_MODE:
			memset(&data, 0, sizeof(data));

			data.device_mode = tbt->alt->vdo;
			data.enter_vdo = tbt->enter_vdo;
			if (tbt->plug[TYPEC_PLUG_SOP_P])
				data.cable_mode = tbt->plug[TYPEC_PLUG_SOP_P]->vdo;

			typec_altmode_notify(alt, TYPEC_STATE_MODAL, &data);
			break;
		case CMD_EXIT_MODE:
			if (tbt->plug[TYPEC_PLUG_SOP_PP])
				tbt->state = TBT_STATE_SOP_PP_EXIT;
			else if (tbt->plug[TYPEC_PLUG_SOP_P])
				tbt->state = TBT_STATE_SOP_P_EXIT;
			break;
		}
		break;
	case CMDT_RSP_NAK:
		switch (cmd) {
		case CMD_ENTER_MODE:
			dev_warn(&alt->dev, "Enter Mode refused\n");
			break;
		default:
			break;
		}
		break;
	default:
		break;
	}

	if (tbt->state != TBT_STATE_IDLE)
		schedule_work(&tbt->work);

	mutex_unlock(&tbt->lock);

	return 0;
}

static int tbt_altmode_activate(struct typec_altmode *alt, int activate)
{
	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
	int ret;

	mutex_lock(&tbt->lock);

	if (activate)
		ret = tbt_enter_modes_ordered(alt);
	else
		ret = typec_altmode_exit(alt);

	mutex_unlock(&tbt->lock);

	return ret;
}

static const struct typec_altmode_ops tbt_altmode_ops = {
	.vdm		= tbt_altmode_vdm,
	.activate	= tbt_altmode_activate
};

static const struct typec_cable_ops tbt_cable_ops = {
	.vdm		= tbt_cable_altmode_vdm,
};

static int tbt_altmode_probe(struct typec_altmode *alt)
{
	struct tbt_altmode *tbt;

	tbt = devm_kzalloc(&alt->dev, sizeof(*tbt), GFP_KERNEL);
	if (!tbt)
		return -ENOMEM;

	INIT_WORK(&tbt->work, tbt_altmode_work);
	mutex_init(&tbt->lock);
	tbt->alt = alt;

	alt->desc = "Thunderbolt3";
	typec_altmode_set_drvdata(alt, tbt);
	typec_altmode_set_ops(alt, &tbt_altmode_ops);

	if (tbt_ready(alt)) {
		if (tbt->plug[TYPEC_PLUG_SOP_P])
			tbt->state = TBT_STATE_SOP_P_ENTER;
		else if (tbt->plug[TYPEC_PLUG_SOP_PP])
			tbt->state = TBT_STATE_SOP_PP_ENTER;
		else
			tbt->state = TBT_STATE_ENTER;
		schedule_work(&tbt->work);
	}

	return 0;
}

static void tbt_altmode_remove(struct typec_altmode *alt)
{
	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);

	for (int i = TYPEC_PLUG_SOP_PP; i >= 0; --i) {
		if (tbt->plug[i])
			typec_altmode_put_plug(tbt->plug[i]);
	}

	if (tbt->cable)
		typec_cable_put(tbt->cable);
}

static bool tbt_ready(struct typec_altmode *alt)
{
	struct tbt_altmode *tbt = typec_altmode_get_drvdata(alt);
	struct typec_altmode *plug;

	if (tbt->cable)
		return true;

	/* Thunderbolt 3 requires a cable with eMarker */
	tbt->cable = typec_cable_get(typec_altmode2port(tbt->alt));
	if (!tbt->cable)
		return false;

	/* We accept systems without SOP' or SOP''. This means the port altmode
	 * driver will be responsible for properly ordering entry/exit.
	 */
	for (int i = 0; i < TYPEC_PLUG_SOP_PP + 1; i++) {
		plug = typec_altmode_get_plug(tbt->alt, i);
		if (!plug)
			continue;

		if (plug->svid != USB_TYPEC_TBT_SID)
			break;

		plug->desc = "Thunderbolt3";
		plug->cable_ops = &tbt_cable_ops;
		typec_altmode_set_drvdata(plug, tbt);

		tbt->plug[i] = plug;
	}

	return true;
}

static const struct typec_device_id tbt_typec_id[] = {
	{ USB_TYPEC_TBT_SID },
	{ }
};
MODULE_DEVICE_TABLE(typec, tbt_typec_id);

static struct typec_altmode_driver tbt_altmode_driver = {
	.id_table = tbt_typec_id,
	.probe = tbt_altmode_probe,
	.remove = tbt_altmode_remove,
	.driver = {
		.name = "typec-thunderbolt",
	}
};
module_typec_altmode_driver(tbt_altmode_driver);

MODULE_AUTHOR("Heikki Krogerus <heikki.krogerus@linux.intel.com>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Thunderbolt3 USB Type-C Alternate Mode");