// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2014-2019 Nuvoton Technology corporation
 *
 * TPM TIS I2C
 *
 * TPM TIS I2C Device Driver Interface for devices that implement the TPM I2C
 * Interface defined by TCG PC Client Platform TPM Profile (PTP) Specification
 * Revision 01.03 v22 at www.trustedcomputinggroup.org
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/wait.h>
#include <linux/acpi.h>
#include <linux/freezer.h>
#include <linux/crc-ccitt.h>

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/gpio.h>
#include <linux/of_irq.h>
#include <linux/of_gpio.h>
#include <linux/tpm.h>
#include "tpm.h"
#include "tpm_tis_core.h"

#define TPM_LOC_SEL                    0x04
#define TPM_I2C_INTERFACE_CAPABILITY   0x30
#define TPM_I2C_DEVICE_ADDRESS         0x38
#define TPM_DATA_CSUM_ENABLE           0x40
#define TPM_DATA_CSUM                  0x44
#define TPM_I2C_DID_VID                        0x48
#define TPM_I2C_RID                    0x4C

//#define I2C_IS_TPM2 1

struct tpm_tis_i2c_phy {
	struct tpm_tis_data priv;
	struct i2c_client *i2c_client;
	bool data_csum;
	u8 *iobuf;
};

static inline struct tpm_tis_i2c_phy *to_tpm_tis_i2c_phy(struct tpm_tis_data *data)
{
	return container_of(data, struct tpm_tis_i2c_phy, priv);
}

static u8 address_to_register(u32 addr)
{
	addr &= 0xFFF;

	switch (addr) {
		// adapt register addresses that have changed compared to
		// older TIS versions
	case TPM_ACCESS(0):
		return 0x04;
	case TPM_LOC_SEL:
		return 0x00;
	case TPM_DID_VID(0):
		return 0x48;
	case TPM_RID(0):
		return 0x4C;
	default:
		return addr;
	}
}

static int tpm_tis_i2c_read_bytes(struct tpm_tis_data *data, u32 addr,
				  u16 len, u8 *result)
{
	struct tpm_tis_i2c_phy *phy = to_tpm_tis_i2c_phy(data);
	int ret = 0;
	int i = 0;
	u8 reg = address_to_register(addr);
	struct i2c_msg msgs[] = {
		{
			.addr = phy->i2c_client->addr,
			.len = sizeof(reg),
			.buf = &reg,
		},
		{
			.addr = phy->i2c_client->addr,
			.len = len,
			.buf = result,
			.flags = I2C_M_RD,
		},
	};

	do {
		ret = i2c_transfer(phy->i2c_client->adapter, msgs,
				   ARRAY_SIZE(msgs));
		usleep_range(250, 300); // wait default GUARD_TIME of 250µs

	} while (ret < 0 && i++ < TPM_RETRY);

	if (ret < 0)
		return ret;


	return 0;
}

static int tpm_tis_i2c_write_bytes(struct tpm_tis_data *data, u32 addr,
				   u16 len, const u8 *value)
{
	struct tpm_tis_i2c_phy *phy = to_tpm_tis_i2c_phy(data);
	int ret = 0;
	int i = 0;

	if (phy->iobuf) {
		if (len > TPM_BUFSIZE - 1)
			return -EIO;

		phy->iobuf[0] = address_to_register(addr);
		memcpy(phy->iobuf + 1, value, len);

		{
			struct i2c_msg msgs[] = {
				{
					.addr = phy->i2c_client->addr,
					.len = len + 1,
					.buf = phy->iobuf,
				},
			};

			do {
				ret = i2c_transfer(phy->i2c_client->adapter,
						   msgs, ARRAY_SIZE(msgs));
				// wait default GUARD_TIME of 250µs
				usleep_range(250, 300);
			} while (ret < 0 && i++ < TPM_RETRY);
		}
	} else {
		u8 reg = address_to_register(addr);

		struct i2c_msg msgs[] = {
			{
				.addr = phy->i2c_client->addr,
				.len = sizeof(reg),
				.buf = &reg,
			},
			{
				.addr = phy->i2c_client->addr,
				.len = len,
				.buf = (u8 *)value,
				.flags = I2C_M_NOSTART,
			},
		};
		do {
			ret = i2c_transfer(phy->i2c_client->adapter, msgs,
					   ARRAY_SIZE(msgs));
			// wait default GUARD_TIME of 250µs
			usleep_range(250, 300);
		} while (ret < 0 && i++ < TPM_RETRY);
	}

	if (ret < 0)
		return ret;


	return 0;
}

static bool tpm_tis_i2c_check_data(struct tpm_tis_data *data,
				   const u8 *buf, size_t len)
{
	struct tpm_tis_i2c_phy *phy = to_tpm_tis_i2c_phy(data);
	u16 crc, crc_tpm;
	int rc;

	if (phy->data_csum) {
		crc = crc_ccitt(0x0000, buf, len);
		rc = tpm_tis_read16(data, TPM_DATA_CSUM, &crc_tpm);
		if (rc < 0)
			return false;

		crc_tpm = be16_to_cpu(crc_tpm);
		return crc == crc_tpm;
	}

	return true;
}

static SIMPLE_DEV_PM_OPS(tpm_tis_pm, tpm_pm_suspend, tpm_tis_resume);

static int csum_state_store(struct tpm_tis_data *data, u8 new_state)
{
	struct tpm_tis_i2c_phy *phy = to_tpm_tis_i2c_phy(data);
	u8 cur_state;
	int rc;

	rc = tpm_tis_i2c_write_bytes(&phy->priv, TPM_DATA_CSUM_ENABLE,
				     1, &new_state);
	if (rc < 0)
		return rc;

	rc = tpm_tis_i2c_read_bytes(&phy->priv, TPM_DATA_CSUM_ENABLE,
				    1, &cur_state);
	if (rc < 0)
		return rc;

	if (new_state == cur_state)
		phy->data_csum = (bool)new_state;

	return rc;
}

static const struct tpm_tis_phy_ops tpm_i2c_phy_ops = {
	.read_bytes = tpm_tis_i2c_read_bytes,
	.write_bytes = tpm_tis_i2c_write_bytes,
	.check_data = tpm_tis_i2c_check_data,
};

static int tpm_tis_i2c_probe(struct i2c_client *dev,
			     const struct i2c_device_id *id)
{
	struct tpm_tis_i2c_phy *phy;
	int rc;
	int CRC_Checksum = 0;
	const u8 loc_init = 0;
	struct device_node *np;

	phy = devm_kzalloc(&dev->dev, sizeof(struct tpm_tis_i2c_phy),
			   GFP_KERNEL);
	if (!phy)
		return -ENOMEM;

	phy->i2c_client = dev;

	if (!i2c_check_functionality(dev->adapter, I2C_FUNC_NOSTART)) {
		phy->iobuf = devm_kmalloc(&dev->dev, TPM_BUFSIZE, GFP_KERNEL);
		if (!phy->iobuf)
			return -ENOMEM;
	}

	// select locality 0 (the driver will access only via locality 0)
	rc = tpm_tis_i2c_write_bytes(&phy->priv, TPM_LOC_SEL, 1, &loc_init);
	if (rc < 0)
		return rc;

	// set CRC checksum calculation enable
	np = dev->dev.of_node;
	if (of_property_read_bool(np, "crc-checksum"))
		CRC_Checksum = 1;

	rc = csum_state_store(&phy->priv, CRC_Checksum);
	if (rc < 0)
		return rc;

	return tpm_tis_core_init(&dev->dev, &phy->priv, -1, &tpm_i2c_phy_ops,
					NULL);
}

static const struct i2c_device_id tpm_tis_i2c_id[] = {
	{"tpm_tis_i2c", 0},
	{}
};
MODULE_DEVICE_TABLE(i2c, tpm_tis_i2c_id);

static const struct of_device_id of_tis_i2c_match[] = {
	{ .compatible = "tcg,tpm-tis-i2c", },
	{}
};
MODULE_DEVICE_TABLE(of, of_tis_i2c_match);

static const struct acpi_device_id acpi_tis_i2c_match[] = {
	{"SMO0768", 0},
	{}
};
MODULE_DEVICE_TABLE(acpi, acpi_tis_i2c_match);

static struct i2c_driver tpm_tis_i2c_driver = {
	.driver = {
		.owner = THIS_MODULE,
		.name = "tpm_tis_i2c",
		.pm = &tpm_tis_pm,
		.of_match_table = of_match_ptr(of_tis_i2c_match),
		.acpi_match_table = ACPI_PTR(acpi_tis_i2c_match),
	},
	.probe = tpm_tis_i2c_probe,
	.id_table = tpm_tis_i2c_id,
};

module_i2c_driver(tpm_tis_i2c_driver);

MODULE_DESCRIPTION("TPM Driver");
MODULE_LICENSE("GPL");