/*
 * STMicroelectronics TPM SPI Linux driver for TPM ST33ZP24
 * Copyright (C) 2009 - 2015  STMicroelectronics
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/module.h>
#include <linux/spi/spi.h>
#include <linux/gpio.h>
#include <linux/of_irq.h>
#include <linux/of_gpio.h>
#include <linux/tpm.h>
#include <linux/platform_data/st33zp24.h>

#include "st33zp24.h"

#define TPM_DATA_FIFO           0x24
#define TPM_INTF_CAPABILITY     0x14

#define TPM_DUMMY_BYTE		0x00

#define MAX_SPI_LATENCY		15
#define LOCALITY0		0

#define ST33ZP24_OK					0x5A
#define ST33ZP24_UNDEFINED_ERR				0x80
#define ST33ZP24_BADLOCALITY				0x81
#define ST33ZP24_TISREGISTER_UKNOWN			0x82
#define ST33ZP24_LOCALITY_NOT_ACTIVATED			0x83
#define ST33ZP24_HASH_END_BEFORE_HASH_START		0x84
#define ST33ZP24_BAD_COMMAND_ORDER			0x85
#define ST33ZP24_INCORECT_RECEIVED_LENGTH		0x86
#define ST33ZP24_TPM_FIFO_OVERFLOW			0x89
#define ST33ZP24_UNEXPECTED_READ_FIFO			0x8A
#define ST33ZP24_UNEXPECTED_WRITE_FIFO			0x8B
#define ST33ZP24_CMDRDY_SET_WHEN_PROCESSING_HASH_END	0x90
#define ST33ZP24_DUMMY_BYTES				0x00

/*
 * TPM command can be up to 2048 byte, A TPM response can be up to
 * 1024 byte.
 * Between command and response, there are latency byte (up to 15
 * usually on st33zp24 2 are enough).
 *
 * Overall when sending a command and expecting an answer we need if
 * worst case:
 * 2048 (for the TPM command) + 1024 (for the TPM answer).  We need
 * some latency byte before the answer is available (max 15).
 * We have 2048 + 1024 + 15.
 */
#define ST33ZP24_SPI_BUFFER_SIZE (TPM_BUFSIZE + (TPM_BUFSIZE / 2) +\
				  MAX_SPI_LATENCY)


struct st33zp24_spi_phy {
	struct spi_device *spi_device;
	struct spi_transfer spi_xfer;
	u8 tx_buf[ST33ZP24_SPI_BUFFER_SIZE];
	u8 rx_buf[ST33ZP24_SPI_BUFFER_SIZE];

	int io_lpcpd;
	int latency;
};

static int st33zp24_status_to_errno(u8 code)
{
	switch (code) {
	case ST33ZP24_OK:
		return 0;
	case ST33ZP24_UNDEFINED_ERR:
	case ST33ZP24_BADLOCALITY:
	case ST33ZP24_TISREGISTER_UKNOWN:
	case ST33ZP24_LOCALITY_NOT_ACTIVATED:
	case ST33ZP24_HASH_END_BEFORE_HASH_START:
	case ST33ZP24_BAD_COMMAND_ORDER:
	case ST33ZP24_UNEXPECTED_READ_FIFO:
	case ST33ZP24_UNEXPECTED_WRITE_FIFO:
	case ST33ZP24_CMDRDY_SET_WHEN_PROCESSING_HASH_END:
		return -EPROTO;
	case ST33ZP24_INCORECT_RECEIVED_LENGTH:
	case ST33ZP24_TPM_FIFO_OVERFLOW:
		return -EMSGSIZE;
	case ST33ZP24_DUMMY_BYTES:
		return -ENOSYS;
	}
	return code;
}

/*
 * st33zp24_spi_send
 * Send byte to the TIS register according to the ST33ZP24 SPI protocol.
 * @param: phy_id, the phy description
 * @param: tpm_register, the tpm tis register where the data should be written
 * @param: tpm_data, the tpm_data to write inside the tpm_register
 * @param: tpm_size, The length of the data
 * @return: should be zero if success else a negative error code.
 */
static int st33zp24_spi_send(void *phy_id, u8 tpm_register, u8 *tpm_data,
			     int tpm_size)
{
	u8 data = 0;
	int total_length = 0, nbr_dummy_bytes = 0, ret = 0;
	struct st33zp24_spi_phy *phy = phy_id;
	struct spi_device *dev = phy->spi_device;
	u8 *tx_buf = (u8 *)phy->spi_xfer.tx_buf;
	u8 *rx_buf = phy->spi_xfer.rx_buf;

	/* Pre-Header */
	data = TPM_WRITE_DIRECTION | LOCALITY0;
	memcpy(tx_buf + total_length, &data, sizeof(data));
	total_length++;
	data = tpm_register;
	memcpy(tx_buf + total_length, &data, sizeof(data));
	total_length++;

	if (tpm_size > 0 && tpm_register == TPM_DATA_FIFO) {
		tx_buf[total_length++] = tpm_size >> 8;
		tx_buf[total_length++] = tpm_size;
	}

	memcpy(&tx_buf[total_length], tpm_data, tpm_size);
	total_length += tpm_size;

	nbr_dummy_bytes = phy->latency;
	memset(&tx_buf[total_length], TPM_DUMMY_BYTE, nbr_dummy_bytes);

	phy->spi_xfer.len = total_length + nbr_dummy_bytes;

	ret = spi_sync_transfer(dev, &phy->spi_xfer, 1);
	if (ret == 0)
		ret = rx_buf[total_length + nbr_dummy_bytes - 1];

	return st33zp24_status_to_errno(ret);
} /* st33zp24_spi_send() */

/*
 * read8_recv
 * Recv byte from the TIS register according to the ST33ZP24 SPI protocol.
 * @param: phy_id, the phy description
 * @param: tpm_register, the tpm tis register where the data should be read
 * @param: tpm_data, the TPM response
 * @param: tpm_size, tpm TPM response size to read.
 * @return: should be zero if success else a negative error code.
 */
static int read8_reg(void *phy_id, u8 tpm_register, u8 *tpm_data, int tpm_size)
{
	u8 data = 0;
	int total_length = 0, nbr_dummy_bytes, ret;
	struct st33zp24_spi_phy *phy = phy_id;
	struct spi_device *dev = phy->spi_device;
	u8 *tx_buf = (u8 *)phy->spi_xfer.tx_buf;
	u8 *rx_buf = phy->spi_xfer.rx_buf;

	/* Pre-Header */
	data = LOCALITY0;
	memcpy(tx_buf + total_length, &data, sizeof(data));
	total_length++;
	data = tpm_register;
	memcpy(tx_buf + total_length, &data, sizeof(data));
	total_length++;

	nbr_dummy_bytes = phy->latency;
	memset(&tx_buf[total_length], TPM_DUMMY_BYTE,
	       nbr_dummy_bytes + tpm_size);

	phy->spi_xfer.len = total_length + nbr_dummy_bytes + tpm_size;

	/* header + status byte + size of the data + status byte */
	ret = spi_sync_transfer(dev, &phy->spi_xfer, 1);
	if (tpm_size > 0 && ret == 0) {
		ret = rx_buf[total_length + nbr_dummy_bytes - 1];

		memcpy(tpm_data, rx_buf + total_length + nbr_dummy_bytes,
		       tpm_size);
	}

	return ret;
} /* read8_reg() */

/*
 * st33zp24_spi_recv
 * Recv byte from the TIS register according to the ST33ZP24 SPI protocol.
 * @param: phy_id, the phy description
 * @param: tpm_register, the tpm tis register where the data should be read
 * @param: tpm_data, the TPM response
 * @param: tpm_size, tpm TPM response size to read.
 * @return: number of byte read successfully: should be one if success.
 */
static int st33zp24_spi_recv(void *phy_id, u8 tpm_register, u8 *tpm_data,
			     int tpm_size)
{
	int ret;

	ret = read8_reg(phy_id, tpm_register, tpm_data, tpm_size);
	if (!st33zp24_status_to_errno(ret))
		return tpm_size;
	return ret;
} /* st33zp24_spi_recv() */

static int evaluate_latency(void *phy_id)
{
	struct st33zp24_spi_phy *phy = phy_id;
	int latency = 1, status = 0;
	u8 data = 0;

	while (!status && latency < MAX_SPI_LATENCY) {
		phy->latency = latency;
		status = read8_reg(phy_id, TPM_INTF_CAPABILITY, &data, 1);
		latency++;
	}
	return latency - 1;
} /* evaluate_latency() */

static const struct st33zp24_phy_ops spi_phy_ops = {
	.send = st33zp24_spi_send,
	.recv = st33zp24_spi_recv,
};

#ifdef CONFIG_OF
static int tpm_stm_spi_of_request_resources(struct st33zp24_spi_phy *phy)
{
	struct device_node *pp;
	struct spi_device *dev = phy->spi_device;
	int gpio;
	int ret;

	pp = dev->dev.of_node;
	if (!pp) {
		dev_err(&dev->dev, "No platform data\n");
		return -ENODEV;
	}

	/* Get GPIO from device tree */
	gpio = of_get_named_gpio(pp, "lpcpd-gpios", 0);
	if (gpio < 0) {
		dev_err(&dev->dev,
			"Failed to retrieve lpcpd-gpios from dts.\n");
		phy->io_lpcpd = -1;
		/*
		 * lpcpd pin is not specified. This is not an issue as
		 * power management can be also managed by TPM specific
		 * commands. So leave with a success status code.
		 */
		return 0;
	}
	/* GPIO request and configuration */
	ret = devm_gpio_request_one(&dev->dev, gpio,
			GPIOF_OUT_INIT_HIGH, "TPM IO LPCPD");
	if (ret) {
		dev_err(&dev->dev, "Failed to request lpcpd pin\n");
		return -ENODEV;
	}
	phy->io_lpcpd = gpio;

	return 0;
}
#else
static int tpm_stm_spi_of_request_resources(struct st33zp24_spi_phy *phy)
{
	return -ENODEV;
}
#endif

static int tpm_stm_spi_request_resources(struct spi_device *dev,
					 struct st33zp24_spi_phy *phy)
{
	struct st33zp24_platform_data *pdata;
	int ret;

	pdata = dev->dev.platform_data;
	if (!pdata) {
		dev_err(&dev->dev, "No platform data\n");
		return -ENODEV;
	}

	/* store for late use */
	phy->io_lpcpd = pdata->io_lpcpd;

	if (gpio_is_valid(pdata->io_lpcpd)) {
		ret = devm_gpio_request_one(&dev->dev,
				pdata->io_lpcpd, GPIOF_OUT_INIT_HIGH,
				"TPM IO_LPCPD");
		if (ret) {
			dev_err(&dev->dev, "%s : reset gpio_request failed\n",
				__FILE__);
			return ret;
		}
	}

	return 0;
}

/*
 * tpm_st33_spi_probe initialize the TPM device
 * @param: dev, the spi_device drescription (TPM SPI description).
 * @return: 0 in case of success.
 *	 or a negative value describing the error.
 */
static int
tpm_st33_spi_probe(struct spi_device *dev)
{
	int ret;
	struct st33zp24_platform_data *pdata;
	struct st33zp24_spi_phy *phy;

	/* Check SPI platform functionnalities */
	if (!dev) {
		pr_info("%s: dev is NULL. Device is not accessible.\n",
			__func__);
		return -ENODEV;
	}

	phy = devm_kzalloc(&dev->dev, sizeof(struct st33zp24_spi_phy),
			   GFP_KERNEL);
	if (!phy)
		return -ENOMEM;

	phy->spi_device = dev;
	pdata = dev->dev.platform_data;
	if (!pdata && dev->dev.of_node) {
		ret = tpm_stm_spi_of_request_resources(phy);
		if (ret)
			return ret;
	} else if (pdata) {
		ret = tpm_stm_spi_request_resources(dev, phy);
		if (ret)
			return ret;
	}

	phy->spi_xfer.tx_buf = phy->tx_buf;
	phy->spi_xfer.rx_buf = phy->rx_buf;

	phy->latency = evaluate_latency(phy);
	if (phy->latency <= 0)
		return -ENODEV;

	return st33zp24_probe(phy, &spi_phy_ops, &dev->dev, dev->irq,
			      phy->io_lpcpd);
}

/*
 * tpm_st33_spi_remove remove the TPM device
 * @param: client, the spi_device drescription (TPM SPI description).
 * @return: 0 in case of success.
 */
static int tpm_st33_spi_remove(struct spi_device *dev)
{
	struct tpm_chip *chip = spi_get_drvdata(dev);

	return st33zp24_remove(chip);
}

static const struct spi_device_id st33zp24_spi_id[] = {
	{TPM_ST33_SPI, 0},
	{}
};
MODULE_DEVICE_TABLE(spi, st33zp24_spi_id);

#ifdef CONFIG_OF
static const struct of_device_id of_st33zp24_spi_match[] = {
	{ .compatible = "st,st33zp24-spi", },
	{}
};
MODULE_DEVICE_TABLE(of, of_st33zp24_spi_match);
#endif

static SIMPLE_DEV_PM_OPS(st33zp24_spi_ops, st33zp24_pm_suspend,
			 st33zp24_pm_resume);

static struct spi_driver tpm_st33_spi_driver = {
	.driver = {
		.owner = THIS_MODULE,
		.name = TPM_ST33_SPI,
		.pm = &st33zp24_spi_ops,
		.of_match_table = of_match_ptr(of_st33zp24_spi_match),
	},
	.probe = tpm_st33_spi_probe,
	.remove = tpm_st33_spi_remove,
	.id_table = st33zp24_spi_id,
};

module_spi_driver(tpm_st33_spi_driver);

MODULE_AUTHOR("TPM support (TPMsupport@list.st.com)");
MODULE_DESCRIPTION("STM TPM 1.2 SPI ST33 Driver");
MODULE_VERSION("1.3.0");
MODULE_LICENSE("GPL");