/*
 * tegra_cpc.c - Access CPC storage blocks through i2c bus
 *
 * Copyright (c) 2014-2018, NVIDIA CORPORATION.  All rights reserved.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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.
 */

#include <linux/module.h>
#include <linux/regmap.h>
#include <linux/io.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/completion.h>

/* misc device */
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/i2c.h>
#include <asm/unaligned.h>
#include <linux/ioctl.h>
#include <linux/types.h>
#include <uapi/linux/tegra_cpc.h>

#define CPC_I2C_DEADLINE_MS 1000
#define TEGRA_CPC_DEBUG 0

/*
 * Helper macro section
 */

/* returns 0 on a successful copy. Returns -ENOMEM otherwise */
inline int tegra_cpc_serialize_field_n(u8 **dest, u8 *source, size_t len,
	size_t *rem_buf_size)
{
	if (unlikely(*rem_buf_size < len))
		return -ENOMEM;
	memcpy(*dest, source, len);
	(*rem_buf_size) -= len;
	(*dest) = &((*dest)[len]);
	return 0;
}

#define TEGRA_CPC_SERIALIZE_FIELD(dest, source, rem_buf_len) \
	tegra_cpc_serialize_field_n(dest, (u8 *) &source, sizeof(source), \
		rem_buf_len)

/* returns 0 on a successful copy. Returns -ENOMEM otherwise */
inline int tegra_cpc_deserialize_field_n(u8 *dest, u8 **source, size_t len,
	size_t *rem_buf_size)
{
	if (unlikely(*rem_buf_size < len))
		return -ENOMEM;
	memcpy(dest, *source, len);
	(*rem_buf_size) -= len;
	(*source) = &((*source)[len]);
	return 0;
}

#define TEGRA_CPC_DESERIALIZE_FIELD(dest, source, rem_buf_len) \
	tegra_cpc_deserialize_field_n((u8 *) &dest, source, sizeof(dest), \
		rem_buf_len)

#define TEGRA_CPC_COPY_TO_VAR(var, source) \
	memcpy(&var, source, sizeof(source))

inline int tegra_cpc_verify_fr_len(u8 length, struct i2c_client *i2c_client)
{
	if (unlikely((length == 0) ||
		(length > CPC_MAX_DATA_SIZE))) {
		dev_err(&i2c_client->dev,
			"The requested size is invalid: %u",
			(unsigned int) length);
		return -EINVAL;
	}
	return 0;
}

/* Local data structure section */
struct cpc_i2c_host {
	struct i2c_client *i2c_client;
	struct regmap *regmap;
	struct i2c_msg readback;

	int irq;
	struct mutex lock;
	struct completion complete;
};

/* There will be at most one uC instance per board */
static atomic_t cpc_in_use;
static struct cpc_i2c_host *cpc_host;

/*
 * Serialization and deserialization logic
 *
 * serialize functions assume buffer is enough to hold the entire fr, and
 * that the content of fr has been verified already
 *
 * deserialize function assumes that the buffer is enough to hold the fr
 */

/* read counter */
static int cpc_serialize_read_counter(struct tegra_cpc_frame *fr, u8 buffer[],
	size_t buf_size) {

	size_t rem_buf_size = buf_size;
	struct tegra_cpc_read_counter_data *fr_cmd = &fr->cmd_data.read_counter;

	if (TEGRA_CPC_SERIALIZE_FIELD(&buffer, fr->req, &rem_buf_size) ||
		TEGRA_CPC_SERIALIZE_FIELD(&buffer, fr_cmd->nonce,
			&rem_buf_size) ||
		TEGRA_CPC_SERIALIZE_FIELD(&buffer, fr_cmd->derivation_value,
			&rem_buf_size))
		return -ENOMEM;

	return buf_size - rem_buf_size;
}

static inline size_t cpc_deserialize_size_read_counter(
		struct tegra_cpc_frame *fr) {
	struct tegra_cpc_read_counter_data *fr_cmd = &fr->cmd_data.read_counter;

	return sizeof(fr_cmd->hmac) + sizeof(fr_cmd->write_counter);
}

static int cpc_deserialize_read_counter(struct tegra_cpc_frame *fr, u8 buffer[],
		size_t rem_buf_size) {
	struct tegra_cpc_read_counter_data *fr_cmd = &fr->cmd_data.read_counter;

	if (TEGRA_CPC_DESERIALIZE_FIELD(fr_cmd->hmac, &buffer, &rem_buf_size) ||
		TEGRA_CPC_DESERIALIZE_FIELD(fr_cmd->write_counter, &buffer,
			&rem_buf_size))
		return -ENOMEM;
	return 0;
}

/* write frame */
static int cpc_serialize_write_frame(struct tegra_cpc_frame *fr, u8 buffer[],
		size_t buf_size) {

	size_t rem_buf_size = buf_size;
	struct tegra_cpc_write_frame_data *fr_cmd = &fr->cmd_data.write_frame;
	size_t oneshot_copy_size = sizeof(fr_cmd->nonce) +
		sizeof(fr_cmd->write_counter) + fr_cmd->length;

	if (TEGRA_CPC_SERIALIZE_FIELD(&buffer, fr->req, &rem_buf_size) ||
		TEGRA_CPC_SERIALIZE_FIELD(&buffer, fr_cmd->hmac,
			&rem_buf_size) ||
		TEGRA_CPC_SERIALIZE_FIELD(&buffer, fr_cmd->length,
			&rem_buf_size))
		return -ENOMEM;

	if (rem_buf_size < oneshot_copy_size)
		return -ENOMEM;

	rem_buf_size -= oneshot_copy_size;

	memcpy(buffer, &fr_cmd->nonce, oneshot_copy_size);
	return buf_size - rem_buf_size;
}

/* read frame */
static int cpc_serialize_read_frame(struct tegra_cpc_frame *fr, u8 buffer[],
		size_t buf_size) {
	size_t rem_buf_size = buf_size;
	struct tegra_cpc_read_frame_data *fr_cmd = &fr->cmd_data.read_frame;

	if (TEGRA_CPC_SERIALIZE_FIELD(&buffer, fr->req, &rem_buf_size) ||
		TEGRA_CPC_SERIALIZE_FIELD(&buffer, fr_cmd->nonce,
			&rem_buf_size) ||
		TEGRA_CPC_SERIALIZE_FIELD(&buffer, fr_cmd->length,
			&rem_buf_size))
		return -ENOMEM;

	return buf_size - rem_buf_size;
}

static inline size_t cpc_deserialize_size_read_frame(
		struct tegra_cpc_frame *fr) {
	struct tegra_cpc_read_frame_data *fr_cmd = &fr->cmd_data.read_frame;

	return sizeof(fr_cmd->hmac) + fr_cmd->length;
}

static int cpc_deserialize_read_frame(struct tegra_cpc_frame *fr, u8 buffer[],
		size_t rem_buf_size) {
	struct tegra_cpc_read_frame_data *fr_cmd = &fr->cmd_data.read_frame;

	if (TEGRA_CPC_DESERIALIZE_FIELD(fr_cmd->hmac, &buffer, &rem_buf_size) ||
		tegra_cpc_deserialize_field_n(fr_cmd->data, &buffer,
			fr_cmd->length, &rem_buf_size))
		return -ENOMEM;
	return 0;
}

/* Get Status */
static int cpc_serialize_get_status(struct tegra_cpc_frame *fr, u8 buffer[],
		size_t buf_size) {
	size_t rem_buf_size = buf_size;

	/* get status can run without any data from the user space */
	u8 req = CPC_GET_RESULT;

	if (TEGRA_CPC_SERIALIZE_FIELD(&buffer, req, &rem_buf_size))
		return -ENOMEM;

	return buf_size - rem_buf_size;
}

static inline size_t cpc_deserialize_size_get_status(
		struct tegra_cpc_frame *fr) {
	return sizeof(fr->hmac) + sizeof(fr->result) +
		sizeof(fr->nonce);
}

static int cpc_deserialize_get_status(struct tegra_cpc_frame *fr, u8 buffer[],
		size_t rem_buf_size) {
	if (TEGRA_CPC_DESERIALIZE_FIELD(fr->hmac, &buffer, &rem_buf_size) ||
		TEGRA_CPC_DESERIALIZE_FIELD(fr->result, &buffer,
			&rem_buf_size) ||
		TEGRA_CPC_DESERIALIZE_FIELD(fr->nonce, &buffer, &rem_buf_size))
		return -ENOMEM;
	return 0;
}

/* Get Version */
static int cpc_serialize_get_version(struct tegra_cpc_frame *fr, u8 buffer[],
		size_t buf_size) {
	size_t rem_buf_size = buf_size;
	struct tegra_cpc_get_version_data *fr_cmd = &fr->cmd_data.get_version;
	u8 req = CPC_GET_VERSION;

	if (TEGRA_CPC_SERIALIZE_FIELD(&buffer, req, &rem_buf_size) ||
		TEGRA_CPC_SERIALIZE_FIELD(&buffer, fr_cmd->nonce,
		&rem_buf_size))
		return -ENOMEM;

	return buf_size - rem_buf_size;
}

static inline size_t cpc_deserialize_size_get_version(
		struct tegra_cpc_frame *fr) {
	struct tegra_cpc_get_version_data *fr_cmd = &fr->cmd_data.get_version;

	return sizeof(fr_cmd->major_ver) + sizeof(fr_cmd->minor_ver);
}

static int cpc_deserialize_get_version(struct tegra_cpc_frame *fr, u8 buffer[],
		size_t rem_buf_size) {
	struct tegra_cpc_get_version_data *fr_cmd = &fr->cmd_data.get_version;

	if (TEGRA_CPC_DESERIALIZE_FIELD(fr_cmd->minor_ver, &buffer,
		&rem_buf_size) ||
		TEGRA_CPC_DESERIALIZE_FIELD(fr_cmd->major_ver, &buffer,
			&rem_buf_size))
		return -ENOMEM;

	return 0;
}

/*
 * I2C related section
 */
static int cpc_send_i2c_msg(struct i2c_client *client, struct i2c_msg *msgs,
				unsigned int num_msg)
{
	int err;

	err = i2c_transfer(client->adapter, msgs, num_msg);
	if (unlikely(err != num_msg)) {
		if (err < 0)
			dev_err(&client->dev,
				"%s: i2c transfer failed. Error: %d\n",
				__func__, err);

		if (err >= 0)
			dev_err(&client->dev,
				"%s: i2c transfer failed. Transferred %d/%u\n",
				__func__, err, num_msg);
		return -EINVAL;
	}

	return 0;
}

/*
 * Issues a given read command and perform deserialization of the read data
 * Assumes the caller has performed all error checks on fr
 */
static int cpc_read_data(struct i2c_client *client, struct tegra_cpc_frame *fr,
	int (*cpc_serialization_strategy)
		(struct tegra_cpc_frame *fr, u8 buffer[], size_t buf_size),
	int expected_resp_len,
	int (*cpc_deserialization_strategy)
		(struct tegra_cpc_frame *fr, u8 buffer[], size_t buf_size))
{
	struct i2c_msg msg[2];
	int ret = 0;
	int packet_len;

	/*
	 * The read command will not send any data. The uC may send more data
	 * then length bytes, if HMAC is involved
	 *
	 * The buffer for reading the data back has to be big enough to hold
	 I the maximum value which can be expressed by the size of cpc_data_len
	 */
	u8 buffer_req[sizeof(struct tegra_cpc_frame)];
	u8 buffer_resp[sizeof(struct tegra_cpc_frame)];

	if (unlikely(!client->adapter))
		return -ENODEV;

	/*
	 * First put header of CPC read command. Start with the write mode flag,
	 * to communicate which command we are sending. Then read the response
	 * on the bus
	 */
	packet_len = cpc_serialization_strategy(fr, buffer_req,
		sizeof(buffer_req));
	if (unlikely(packet_len <= 0)) {
		dev_err(&client->dev, "Serialization failure: %d\n",
			packet_len);
		return -EINVAL;
	}

	msg[0].addr = client->addr;
	msg[0].len = (__u16) packet_len;
	msg[0].flags = 0;
	msg[0].buf = buffer_req;
	/*
	 * The second i2c packet is empty, as it is only a buffer space for
	 * reading the requested data back
	 */
	msg[1].addr = client->addr;
	msg[1].len = expected_resp_len;
	msg[1].flags = I2C_M_RD;
	msg[1].buf = buffer_resp;
	ret = cpc_send_i2c_msg(client, msg,
		sizeof(msg) / sizeof(struct i2c_msg));
	if (unlikely(ret))
		return ret;

	ret = cpc_deserialization_strategy(fr, buffer_resp, expected_resp_len);

	return ret;
}

/*
 * Executes a write command.
 */
static int cpc_write_data(struct i2c_client *client, struct tegra_cpc_frame *fr,
	int (*cpc_serialization_strategy)
		(struct tegra_cpc_frame *fr, u8 buffer[], size_t buf_size)) {
	struct i2c_msg msg[1];
	int packet_len;
	u8 buffer_req[sizeof(struct tegra_cpc_frame)];

	if (unlikely(!client->adapter))
		return -ENODEV;

	packet_len = cpc_serialization_strategy(fr, buffer_req,
		sizeof(buffer_req));
	if (unlikely(packet_len <= 0)) {
		dev_err(&client->dev, "Serialization failure: %d\n",
			packet_len);
		return -EINVAL;
	}
	msg[0].addr = client->addr;
	msg[0].len = (__u16) packet_len;
	msg[0].flags = 0;
	msg[0].buf = buffer_req;

	return cpc_send_i2c_msg(client, msg,
		sizeof(msg) / sizeof(struct i2c_msg));
}

/*
 * Command from user space handling section
 */

/* Error checks against the content of data struct must be done here */
static int _cpc_do_data(struct cpc_i2c_host *cpc, struct tegra_cpc_frame *fr)
{
	int err;
	u32 req_nonce;
	u32 resp_nonce;

	mutex_lock(&cpc->lock);
	fr->result = CPC_RESULT_UNKNOWN_REQUEST;

	/* Each command's input error checked here */
	switch (fr->req) {
	case CPC_READ_M_COUNT:
		TEGRA_CPC_COPY_TO_VAR(req_nonce,
			fr->cmd_data.read_counter.nonce);
		err = cpc_read_data(cpc->i2c_client, fr,
			cpc_serialize_read_counter,
			cpc_deserialize_size_read_counter(fr),
			cpc_deserialize_read_counter);
		break;

	case CPC_READ_FRAME:
		if (tegra_cpc_verify_fr_len(fr->cmd_data.read_frame.length,
				cpc->i2c_client)) {
			fr->result = CPC_RESULT_DATA_LENGTH_MISMATCH;
			err = -EINVAL;
			goto fail;
		}
		TEGRA_CPC_COPY_TO_VAR(req_nonce, fr->cmd_data.read_frame.nonce);
		err = cpc_read_data(cpc->i2c_client, fr,
			cpc_serialize_read_frame,
			cpc_deserialize_size_read_frame(fr),
			cpc_deserialize_read_frame);
		break;

	case CPC_WRITE_FRAME:
		if (tegra_cpc_verify_fr_len(fr->cmd_data.write_frame.length,
				cpc->i2c_client)) {
			fr->result = CPC_RESULT_DATA_LENGTH_MISMATCH;
			err = -EINVAL;
			goto fail;
		}
		init_completion(&cpc->complete);
		TEGRA_CPC_COPY_TO_VAR(req_nonce,
			fr->cmd_data.write_frame.nonce);
		err = cpc_write_data(cpc->i2c_client, fr,
				cpc_serialize_write_frame);

		if (!err && !wait_for_completion_timeout(&cpc->complete,
				msecs_to_jiffies(CPC_I2C_DEADLINE_MS))) {
			dev_err(&cpc->i2c_client->dev,
				"%s timeout on write complete\n", __func__);
			fr->result = CPC_RESULT_WRITE_FAILURE;
			err = -ETIMEDOUT;
		}
		break;

	case CPC_GET_VERSION:
		TEGRA_CPC_COPY_TO_VAR(req_nonce,
			fr->cmd_data.get_version.nonce);
		err = cpc_read_data(cpc->i2c_client, fr,
			cpc_serialize_get_version,
			cpc_deserialize_size_get_version(fr),
			cpc_deserialize_get_version);
		break;

	default:
		err = -EINVAL;
		dev_err(&cpc->i2c_client->dev,
			"unsupported CPC command id %08x\n", fr->req);
	}

	if (err)
		goto fail;

	/* get status should run only when a command was ran successfully */
	err = cpc_read_data(cpc->i2c_client, fr,
		cpc_serialize_get_status,
		cpc_deserialize_size_get_status(fr),
		cpc_deserialize_get_status);

	if (unlikely(err)) {
		dev_err(&cpc->i2c_client->dev,
			"failed to run get status command: %d\n", err);
		fr->result = CPC_RESULT_UNEXPECTED_CONDITION;
		goto fail;
	}

	/*
	 * The request was sent to uC, and uC responded.
	 * Make sure the response is for the request sent.
	 */
	TEGRA_CPC_COPY_TO_VAR(resp_nonce, fr->nonce);
	if (unlikely(req_nonce != resp_nonce)) {
		dev_err(&cpc->i2c_client->dev,
			"Request nonce (%08x) mismatching response nonce (%08x)\n",
			req_nonce, resp_nonce);
		err = -EINVAL;
		fr->result = CPC_RESULT_UNEXPECTED_CONDITION;
	}

fail:
	mutex_unlock(&cpc->lock);
	return err;
}

static int cpc_open(struct inode *inode, struct file *filp)
{
	if (atomic_xchg(&cpc_in_use, 1))
		return -EBUSY;

	if (!cpc_host) {
		pr_info("CPC is not ready\n");
		return -EBADF;
	}

	filp->private_data = cpc_host;

	return nonseekable_open(inode, filp);
}

static int cpc_release(struct inode *inode, struct file *filp)
{
	WARN_ON(!atomic_xchg(&cpc_in_use, 0));
	return 0;
}

static long cpc_ioctl(struct file *file,
			unsigned int cmd, unsigned long arg)
{
	struct cpc_i2c_host *cpc = file->private_data;
	struct tegra_cpc_frame *cpc_fr = NULL;
	long err = 0;

	if (_IOC_TYPE(cmd) != NVCPC_IOC_MAGIC) {
		err = -ENOTTY;
		goto fail;
	}

	if (_IOC_NR(cmd) > NVCPC_IOCTL_DO_IO) {
		err = -ENOTTY;
		goto fail;
	}

	switch (cmd) {
	case NVCPC_IOCTL_DO_IO:
		cpc_fr = kmalloc(sizeof(struct tegra_cpc_frame), GFP_KERNEL);
		if (!cpc_fr) {
			pr_err("%s: failed to allocate memory\n", __func__);
			err = -ENOMEM;
			goto fail;
		}

		if (copy_from_user(cpc_fr, (const void __user *)arg,
					sizeof(struct tegra_cpc_frame))) {
			err = -EFAULT;
			goto fail;
		}

		err = _cpc_do_data(cpc, cpc_fr);

		if (copy_to_user((void __user *)arg, cpc_fr,
					sizeof(struct tegra_cpc_frame))) {
			err = -EFAULT;
			goto fail;
		}
		break;
	default:
		pr_err("CPC: unsupported ioctl\n");
		err =  -EINVAL;
		goto fail;
	}

fail:
	kfree(cpc_fr);
	return err;
}

/*
 * IRQ handling section
 */
static irqreturn_t cpc_irq(int irq, void *data)
{
	struct cpc_i2c_host *cpc = data;

	complete(&cpc->complete);
	return IRQ_HANDLED;
}

/*
 * Driver setup section
 */
static const struct file_operations cpc_dev_fops = {
	.owner = THIS_MODULE,
	.open = cpc_open,
	.release = cpc_release,
	.unlocked_ioctl = cpc_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl = cpc_ioctl,
#endif
};

static struct miscdevice cpc_dev = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "tegra_cpc",
	.fops = &cpc_dev_fops,
};

static int cpc_i2c_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	int err = 0;

	/* Initialize stack variables and structures */
	cpc_host = kzalloc(sizeof(struct cpc_i2c_host), GFP_KERNEL);
	if (!cpc_host) {
		pr_err("unable to allocate memory\n");
		return -ENOMEM;
	}

	/* Setup I2C */
	cpc_host->i2c_client = client;
	i2c_set_clientdata(client, cpc_host);
	cpc_host->irq = client->irq;
	mutex_init(&cpc_host->lock);

	/* Setup IRQ */
	if (cpc_host->irq < 0) {
		dev_err(&client->dev,
			"Unable to enable IRQ\n");
		err = -EINVAL;
		goto pre_irq_fail;
	} else {
		/*
		 * In case the IRQ fires before complete is initialized,
		 * initialize complete now and over write later
		 *
		 * Another option is to disable IRQ until the host is
		 * ready to handle the IRQ, but that causes recurring burden
		 * of re-enabling and re-disabling IRQ
		 */
		init_completion(&cpc_host->complete);
		err = request_threaded_irq(cpc_host->irq, cpc_irq, NULL,
					IRQF_TRIGGER_FALLING,
					dev_name(&client->dev), cpc_host);
		if (err) {
			dev_err(&client->dev, "%s: request irq failed %d\n",
				__func__, err);
			err = -EINVAL;
			goto pre_irq_fail;
		}
	}

	/* setup misc device for userspace io */
	if (misc_register(&cpc_dev)) {
		pr_err("%s: misc device register failed\n", __func__);
		err = -ENOMEM;
		goto fail;
	}

	dev_info(&client->dev, "host driver for CPC\n");
	return 0;

fail:
	free_irq(cpc_host->irq, cpc_host);
pre_irq_fail:
	dev_set_drvdata(&client->dev, NULL);
	mutex_destroy(&cpc_host->lock);
	kfree(cpc_host);
	return err;
}

static int cpc_i2c_remove(struct i2c_client *client)
{
	struct cpc_i2c_host *cpc_host = dev_get_drvdata(&client->dev);

	mutex_destroy(&cpc_host->lock);
	free_irq(cpc_host->irq, cpc_host);
	kfree(cpc_host);
	cpc_host = NULL;
	return 0;
}

static const struct of_device_id cpc_i2c_of_match_table[] = {
	{ .compatible = "nvidia,cpc", },
	{},
};

static const struct i2c_device_id cpc_i2c_id[] = {
	{ "cpc", 0 },
	{ }
};

MODULE_DEVICE_TABLE(i2c, cpc_i2c_id);

static struct i2c_driver cpc_i2c_driver = {
	.driver = {
		.name = "cpc",
		.owner = THIS_MODULE,
		.of_match_table = cpc_i2c_of_match_table,
	},
	.probe = cpc_i2c_probe,
	.remove = cpc_i2c_remove,
	.id_table = cpc_i2c_id,
};

module_i2c_driver(cpc_i2c_driver);

MODULE_AUTHOR("Sang-Hun Lee");
MODULE_DESCRIPTION("Content protection misc driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("i2c:cpc_i2c");