/*
 * Copyright (C) 2012,2013 Infineon Technologies
 *
 * Authors:
 * Peter Huewe <peter.huewe@infineon.com>
 *
 * Device driver for TCG/TCPA TPM (trusted platform module).
 * Specifications at www.trustedcomputinggroup.org
 *
 * This device driver implements the TPM interface as defined in
 * the TCG TPM Interface Spec version 1.2, revision 1.0 and the
 * Infineon I2C Protocol Stack Specification v0.20.
 *
 * It is based on the original tpm_tis device driver from Leendert van
 * Dorn and Kyleen Hall.
 *
 * 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, version 2 of the
 * License.
 *
 *
 */
#include <linux/i2c.h>
#include <linux/module.h>
#include <linux/wait.h>
#include "tpm.h"

/* max. buffer size supported by our TPM */
#define TPM_BUFSIZE 1260

/* max. number of iterations after I2C NAK */
#define MAX_COUNT 3

#define SLEEP_DURATION_LOW 55
#define SLEEP_DURATION_HI 65

/* max. number of iterations after I2C NAK for 'long' commands
 * we need this especially for sending TPM_READY, since the cleanup after the
 * transtion to the ready state may take some time, but it is unpredictable
 * how long it will take.
 */
#define MAX_COUNT_LONG 50

#define SLEEP_DURATION_LONG_LOW 200
#define SLEEP_DURATION_LONG_HI 220

/* After sending TPM_READY to 'reset' the TPM we have to sleep even longer */
#define SLEEP_DURATION_RESET_LOW 2400
#define SLEEP_DURATION_RESET_HI 2600

/* we want to use usleep_range instead of msleep for the 5ms TPM_TIMEOUT */
#define TPM_TIMEOUT_US_LOW (TPM_TIMEOUT * 1000)
#define TPM_TIMEOUT_US_HI  (TPM_TIMEOUT_US_LOW + 2000)

/* expected value for DIDVID register */
#define TPM_TIS_I2C_DID_VID_9635 0xd1150b00L
#define TPM_TIS_I2C_DID_VID_9645 0x001a15d1L

enum i2c_chip_type {
        SLB9635,
        SLB9645,
        UNKNOWN,
};

/* Structure to store I2C TPM specific stuff */
struct tpm_inf_dev {
        struct i2c_client *client;
        int locality;
        u8 buf[TPM_BUFSIZE + sizeof(u8)]; /* max. buffer size + addr */
        struct tpm_chip *chip;
        enum i2c_chip_type chip_type;
        unsigned int adapterlimit;
};

static struct tpm_inf_dev tpm_dev;

/*
 * iic_tpm_read() - read from TPM register
 * @addr: register address to read from
 * @buffer: provided by caller
 * @len: number of bytes to read
 *
 * Read len bytes from TPM register and put them into
 * buffer (little-endian format, i.e. first byte is put into buffer[0]).
 *
 * NOTE: TPM is big-endian for multi-byte values. Multi-byte
 * values have to be swapped.
 *
 * NOTE: We can't unfortunately use the combined read/write functions
 * provided by the i2c core as the TPM currently does not support the
 * repeated start condition and due to it's special requirements.
 * The i2c_smbus* functions do not work for this chip.
 *
 * Return -EIO on error, 0 on success.
 */
static int iic_tpm_read(u8 addr, u8 *buffer, size_t len)
{

        struct i2c_msg msg1 = {
                .addr = tpm_dev.client->addr,
                .len = 1,
                .buf = &addr
        };
        struct i2c_msg msg2 = {
                .addr = tpm_dev.client->addr,
                .flags = I2C_M_RD,
                .len = len,
                .buf = buffer
        };
        struct i2c_msg msgs[] = {msg1, msg2};

        int rc = 0;
        int count;
        unsigned int msglen = len;

        /* Lock the adapter for the duration of the whole sequence. */
        if (!tpm_dev.client->adapter->algo->master_xfer)
                return -EOPNOTSUPP;
        i2c_lock_bus(tpm_dev.client->adapter, I2C_LOCK_SEGMENT);

        if (tpm_dev.chip_type == SLB9645) {
                /* use a combined read for newer chips
                 * unfortunately the smbus functions are not suitable due to
                 * the 32 byte limit of the smbus.
                 * retries should usually not be needed, but are kept just to
                 * be on the safe side.
                 */
                for (count = 0; count < MAX_COUNT; count++) {
                        rc = __i2c_transfer(tpm_dev.client->adapter, msgs, 2);
                        if (rc > 0)
                                break;  /* break here to skip sleep */
                        usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);
                }
        } else {
                /* Expect to send one command message and one data message, but
                 * support looping over each or both if necessary.
                 */
                while (len > 0) {
                        /* slb9635 protocol should work in all cases */
                        for (count = 0; count < MAX_COUNT; count++) {
                                rc = __i2c_transfer(tpm_dev.client->adapter,
                                                    &msg1, 1);
                                if (rc > 0)
                                        break;  /* break here to skip sleep */

                                usleep_range(SLEEP_DURATION_LOW,
                                             SLEEP_DURATION_HI);
                        }

                        if (rc <= 0)
                                goto out;

                        /* After the TPM has successfully received the register
                         * address it needs some time, thus we're sleeping here
                         * again, before retrieving the data
                         */
                        for (count = 0; count < MAX_COUNT; count++) {
                                if (tpm_dev.adapterlimit) {
                                        msglen = min_t(unsigned int,
                                                       tpm_dev.adapterlimit,
                                                       len);
                                        msg2.len = msglen;
                                }
                                usleep_range(SLEEP_DURATION_LOW,
                                             SLEEP_DURATION_HI);
                                rc = __i2c_transfer(tpm_dev.client->adapter,
                                                    &msg2, 1);
                                if (rc > 0) {
                                        /* Since len is unsigned, make doubly
                                         * sure we do not underflow it.
                                         */
                                        if (msglen > len)
                                                len = 0;
                                        else
                                                len -= msglen;
                                        msg2.buf += msglen;
                                        break;
                                }
                                /* If the I2C adapter rejected the request (e.g
                                 * when the quirk read_max_len < len) fall back
                                 * to a sane minimum value and try again.
                                 */
                                if (rc == -EOPNOTSUPP)
                                        tpm_dev.adapterlimit =
                                                        I2C_SMBUS_BLOCK_MAX;
                        }

                        if (rc <= 0)
                                goto out;
                }
        }

out:
        i2c_unlock_bus(tpm_dev.client->adapter, I2C_LOCK_SEGMENT);
        /* take care of 'guard time' */
        usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);

        /* __i2c_transfer returns the number of successfully transferred
         * messages.
         * So rc should be greater than 0 here otherwise we have an error.
         */
        if (rc <= 0)
                return -EIO;

        return 0;
}

static int iic_tpm_write_generic(u8 addr, u8 *buffer, size_t len,
                                 unsigned int sleep_low,
                                 unsigned int sleep_hi, u8 max_count)
{
        int rc = -EIO;
        int count;

        struct i2c_msg msg1 = {
                .addr = tpm_dev.client->addr,
                .len = len + 1,
                .buf = tpm_dev.buf
        };

        if (len > TPM_BUFSIZE)
                return -EINVAL;

        if (!tpm_dev.client->adapter->algo->master_xfer)
                return -EOPNOTSUPP;
        i2c_lock_bus(tpm_dev.client->adapter, I2C_LOCK_SEGMENT);

        /* prepend the 'register address' to the buffer */
        tpm_dev.buf[0] = addr;
        memcpy(&(tpm_dev.buf[1]), buffer, len);

        /*
         * NOTE: We have to use these special mechanisms here and unfortunately
         * cannot rely on the standard behavior of i2c_transfer.
         * Even for newer chips the smbus functions are not
         * suitable due to the 32 byte limit of the smbus.
         */
        for (count = 0; count < max_count; count++) {
                rc = __i2c_transfer(tpm_dev.client->adapter, &msg1, 1);
                if (rc > 0)
                        break;
                usleep_range(sleep_low, sleep_hi);
        }

        i2c_unlock_bus(tpm_dev.client->adapter, I2C_LOCK_SEGMENT);
        /* take care of 'guard time' */
        usleep_range(SLEEP_DURATION_LOW, SLEEP_DURATION_HI);

        /* __i2c_transfer returns the number of successfully transferred
         * messages.
         * So rc should be greater than 0 here otherwise we have an error.
         */
        if (rc <= 0)
                return -EIO;

        return 0;
}

/*
 * iic_tpm_write() - write to TPM register
 * @addr: register address to write to
 * @buffer: containing data to be written
 * @len: number of bytes to write
 *
 * Write len bytes from provided buffer to TPM register (little
 * endian format, i.e. buffer[0] is written as first byte).
 *
 * NOTE: TPM is big-endian for multi-byte values. Multi-byte
 * values have to be swapped.
 *
 * NOTE: use this function instead of the iic_tpm_write_generic function.
 *
 * Return -EIO on error, 0 on success
 */
static int iic_tpm_write(u8 addr, u8 *buffer, size_t len)
{
        return iic_tpm_write_generic(addr, buffer, len, SLEEP_DURATION_LOW,
                                     SLEEP_DURATION_HI, MAX_COUNT);
}

/*
 * This function is needed especially for the cleanup situation after
 * sending TPM_READY
 * */
static int iic_tpm_write_long(u8 addr, u8 *buffer, size_t len)
{
        return iic_tpm_write_generic(addr, buffer, len, SLEEP_DURATION_LONG_LOW,
                                     SLEEP_DURATION_LONG_HI, MAX_COUNT_LONG);
}

enum tis_access {
        TPM_ACCESS_VALID = 0x80,
        TPM_ACCESS_ACTIVE_LOCALITY = 0x20,
        TPM_ACCESS_REQUEST_PENDING = 0x04,
        TPM_ACCESS_REQUEST_USE = 0x02,
};

enum tis_status {
        TPM_STS_VALID = 0x80,
        TPM_STS_COMMAND_READY = 0x40,
        TPM_STS_GO = 0x20,
        TPM_STS_DATA_AVAIL = 0x10,
        TPM_STS_DATA_EXPECT = 0x08,
};

enum tis_defaults {
        TIS_SHORT_TIMEOUT = 750,        /* ms */
        TIS_LONG_TIMEOUT = 2000,        /* 2 sec */
};

#define TPM_ACCESS(l)                   (0x0000 | ((l) << 4))
#define TPM_STS(l)                      (0x0001 | ((l) << 4))
#define TPM_DATA_FIFO(l)                (0x0005 | ((l) << 4))
#define TPM_DID_VID(l)                  (0x0006 | ((l) << 4))

static bool check_locality(struct tpm_chip *chip, int loc)
{
        u8 buf;
        int rc;

        rc = iic_tpm_read(TPM_ACCESS(loc), &buf, 1);
        if (rc < 0)
                return false;

        if ((buf & (TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID)) ==
            (TPM_ACCESS_ACTIVE_LOCALITY | TPM_ACCESS_VALID)) {
                tpm_dev.locality = loc;
                return true;
        }

        return false;
}

/* implementation similar to tpm_tis */
static void release_locality(struct tpm_chip *chip, int loc, int force)
{
        u8 buf;
        if (iic_tpm_read(TPM_ACCESS(loc), &buf, 1) < 0)
                return;

        if (force || (buf & (TPM_ACCESS_REQUEST_PENDING | TPM_ACCESS_VALID)) ==
            (TPM_ACCESS_REQUEST_PENDING | TPM_ACCESS_VALID)) {
                buf = TPM_ACCESS_ACTIVE_LOCALITY;
                iic_tpm_write(TPM_ACCESS(loc), &buf, 1);
        }
}

static int request_locality(struct tpm_chip *chip, int loc)
{
        unsigned long stop;
        u8 buf = TPM_ACCESS_REQUEST_USE;

        if (check_locality(chip, loc))
                return loc;

        iic_tpm_write(TPM_ACCESS(loc), &buf, 1);

        /* wait for burstcount */
        stop = jiffies + chip->timeout_a;
        do {
                if (check_locality(chip, loc))
                        return loc;
                usleep_range(TPM_TIMEOUT_US_LOW, TPM_TIMEOUT_US_HI);
        } while (time_before(jiffies, stop));

        return -ETIME;
}

static u8 tpm_tis_i2c_status(struct tpm_chip *chip)
{
        /* NOTE: since I2C read may fail, return 0 in this case --> time-out */
        u8 buf = 0xFF;
        u8 i = 0;

        do {
                if (iic_tpm_read(TPM_STS(tpm_dev.locality), &buf, 1) < 0)
                        return 0;

                i++;
        /* if locallity is set STS should not be 0xFF */
        } while ((buf == 0xFF) && i < 10);

        return buf;
}

static void tpm_tis_i2c_ready(struct tpm_chip *chip)
{
        /* this causes the current command to be aborted */
        u8 buf = TPM_STS_COMMAND_READY;
        iic_tpm_write_long(TPM_STS(tpm_dev.locality), &buf, 1);
}

static ssize_t get_burstcount(struct tpm_chip *chip)
{
        unsigned long stop;
        ssize_t burstcnt;
        u8 buf[3];

        /* wait for burstcount */
        /* which timeout value, spec has 2 answers (c & d) */
        stop = jiffies + chip->timeout_d;
        do {
                /* Note: STS is little endian */
                if (iic_tpm_read(TPM_STS(tpm_dev.locality)+1, buf, 3) < 0)
                        burstcnt = 0;
                else
                        burstcnt = (buf[2] << 16) + (buf[1] << 8) + buf[0];

                if (burstcnt)
                        return burstcnt;

                usleep_range(TPM_TIMEOUT_US_LOW, TPM_TIMEOUT_US_HI);
        } while (time_before(jiffies, stop));
        return -EBUSY;
}

static int wait_for_stat(struct tpm_chip *chip, u8 mask, unsigned long timeout,
                         int *status)
{
        unsigned long stop;

        /* check current status */
        *status = tpm_tis_i2c_status(chip);
        if ((*status != 0xFF) && (*status & mask) == mask)
                return 0;

        stop = jiffies + timeout;
        do {
                /* since we just checked the status, give the TPM some time */
                usleep_range(TPM_TIMEOUT_US_LOW, TPM_TIMEOUT_US_HI);
                *status = tpm_tis_i2c_status(chip);
                if ((*status & mask) == mask)
                        return 0;

        } while (time_before(jiffies, stop));

        return -ETIME;
}

static int recv_data(struct tpm_chip *chip, u8 *buf, size_t count)
{
        size_t size = 0;
        ssize_t burstcnt;
        u8 retries = 0;
        int rc;

        while (size < count) {
                burstcnt = get_burstcount(chip);

                /* burstcnt < 0 = TPM is busy */
                if (burstcnt < 0)
                        return burstcnt;

                /* limit received data to max. left */
                if (burstcnt > (count - size))
                        burstcnt = count - size;

                rc = iic_tpm_read(TPM_DATA_FIFO(tpm_dev.locality),
                                  &(buf[size]), burstcnt);
                if (rc == 0)
                        size += burstcnt;
                else if (rc < 0)
                        retries++;

                /* avoid endless loop in case of broken HW */
                if (retries > MAX_COUNT_LONG)
                        return -EIO;
        }
        return size;
}

static int tpm_tis_i2c_recv(struct tpm_chip *chip, u8 *buf, size_t count)
{
        int size = 0;
        int status;
        u32 expected;

        if (count < TPM_HEADER_SIZE) {
                size = -EIO;
                goto out;
        }

        /* read first 10 bytes, including tag, paramsize, and result */
        size = recv_data(chip, buf, TPM_HEADER_SIZE);
        if (size < TPM_HEADER_SIZE) {
                dev_err(&chip->dev, "Unable to read header\n");
                goto out;
        }

        expected = be32_to_cpu(*(__be32 *)(buf + 2));
        if (((size_t) expected > count) || (expected < TPM_HEADER_SIZE)) {
                size = -EIO;
                goto out;
        }

        size += recv_data(chip, &buf[TPM_HEADER_SIZE],
                          expected - TPM_HEADER_SIZE);
        if (size < expected) {
                dev_err(&chip->dev, "Unable to read remainder of result\n");
                size = -ETIME;
                goto out;
        }

        wait_for_stat(chip, TPM_STS_VALID, chip->timeout_c, &status);
        if (status & TPM_STS_DATA_AVAIL) {      /* retry? */
                dev_err(&chip->dev, "Error left over data\n");
                size = -EIO;
                goto out;
        }

out:
        tpm_tis_i2c_ready(chip);
        /* The TPM needs some time to clean up here,
         * so we sleep rather than keeping the bus busy
         */
        usleep_range(SLEEP_DURATION_RESET_LOW, SLEEP_DURATION_RESET_HI);
        release_locality(chip, tpm_dev.locality, 0);
        return size;
}

static int tpm_tis_i2c_send(struct tpm_chip *chip, u8 *buf, size_t len)
{
        int rc, status;
        ssize_t burstcnt;
        size_t count = 0;
        u8 retries = 0;
        u8 sts = TPM_STS_GO;

        if (len > TPM_BUFSIZE)
                return -E2BIG;  /* command is too long for our tpm, sorry */

        if (request_locality(chip, 0) < 0)
                return -EBUSY;

        status = tpm_tis_i2c_status(chip);
        if ((status & TPM_STS_COMMAND_READY) == 0) {
                tpm_tis_i2c_ready(chip);
                if (wait_for_stat
                    (chip, TPM_STS_COMMAND_READY,
                     chip->timeout_b, &status) < 0) {
                        rc = -ETIME;
                        goto out_err;
                }
        }

        while (count < len - 1) {
                burstcnt = get_burstcount(chip);

                /* burstcnt < 0 = TPM is busy */
                if (burstcnt < 0)
                        return burstcnt;

                if (burstcnt > (len - 1 - count))
                        burstcnt = len - 1 - count;

                rc = iic_tpm_write(TPM_DATA_FIFO(tpm_dev.locality),
                                   &(buf[count]), burstcnt);
                if (rc == 0)
                        count += burstcnt;
                else if (rc < 0)
                        retries++;

                /* avoid endless loop in case of broken HW */
                if (retries > MAX_COUNT_LONG) {
                        rc = -EIO;
                        goto out_err;
                }

                wait_for_stat(chip, TPM_STS_VALID,
                              chip->timeout_c, &status);

                if ((status & TPM_STS_DATA_EXPECT) == 0) {
                        rc = -EIO;
                        goto out_err;
                }
        }

        /* write last byte */
        iic_tpm_write(TPM_DATA_FIFO(tpm_dev.locality), &(buf[count]), 1);
        wait_for_stat(chip, TPM_STS_VALID, chip->timeout_c, &status);
        if ((status & TPM_STS_DATA_EXPECT) != 0) {
                rc = -EIO;
                goto out_err;
        }

        /* go and do it */
        iic_tpm_write(TPM_STS(tpm_dev.locality), &sts, 1);

        return len;
out_err:
        tpm_tis_i2c_ready(chip);
        /* The TPM needs some time to clean up here,
         * so we sleep rather than keeping the bus busy
         */
        usleep_range(SLEEP_DURATION_RESET_LOW, SLEEP_DURATION_RESET_HI);
        release_locality(chip, tpm_dev.locality, 0);
        return rc;
}

static bool tpm_tis_i2c_req_canceled(struct tpm_chip *chip, u8 status)
{
        return (status == TPM_STS_COMMAND_READY);
}

static const struct tpm_class_ops tpm_tis_i2c = {
        .flags = TPM_OPS_AUTO_STARTUP,
        .status = tpm_tis_i2c_status,
        .recv = tpm_tis_i2c_recv,
        .send = tpm_tis_i2c_send,
        .cancel = tpm_tis_i2c_ready,
        .req_complete_mask = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
        .req_complete_val = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
        .req_canceled = tpm_tis_i2c_req_canceled,
};

static int tpm_tis_i2c_init(struct device *dev)
{
        u32 vendor;
        int rc = 0;
        struct tpm_chip *chip;

        chip = tpmm_chip_alloc(dev, &tpm_tis_i2c);
        if (IS_ERR(chip))
                return PTR_ERR(chip);

        /* Default timeouts */
        chip->timeout_a = msecs_to_jiffies(TIS_SHORT_TIMEOUT);
        chip->timeout_b = msecs_to_jiffies(TIS_LONG_TIMEOUT);
        chip->timeout_c = msecs_to_jiffies(TIS_SHORT_TIMEOUT);
        chip->timeout_d = msecs_to_jiffies(TIS_SHORT_TIMEOUT);

        if (request_locality(chip, 0) != 0) {
                dev_err(dev, "could not request locality\n");
                rc = -ENODEV;
                goto out_err;
        }

        /* read four bytes from DID_VID register */
        if (iic_tpm_read(TPM_DID_VID(0), (u8 *)&vendor, 4) < 0) {
                dev_err(dev, "could not read vendor id\n");
                rc = -EIO;
                goto out_release;
        }

        if (vendor == TPM_TIS_I2C_DID_VID_9645) {
                tpm_dev.chip_type = SLB9645;
        } else if (vendor == TPM_TIS_I2C_DID_VID_9635) {
                tpm_dev.chip_type = SLB9635;
        } else {
                dev_err(dev, "vendor id did not match! ID was %08x\n", vendor);
                rc = -ENODEV;
                goto out_release;
        }

        dev_info(dev, "1.2 TPM (device-id 0x%X)\n", vendor >> 16);

        tpm_dev.chip = chip;

        return tpm_chip_register(chip);
out_release:
        release_locality(chip, tpm_dev.locality, 1);
        tpm_dev.client = NULL;
out_err:
        return rc;
}

static const struct i2c_device_id tpm_tis_i2c_table[] = {
        {"tpm_i2c_infineon"},
        {"slb9635tt"},
        {"slb9645tt"},
        {},
};

MODULE_DEVICE_TABLE(i2c, tpm_tis_i2c_table);

#ifdef CONFIG_OF
static const struct of_device_id tpm_tis_i2c_of_match[] = {
        {.compatible = "infineon,tpm_i2c_infineon"},
        {.compatible = "infineon,slb9635tt"},
        {.compatible = "infineon,slb9645tt"},
        {},
};
MODULE_DEVICE_TABLE(of, tpm_tis_i2c_of_match);
#endif

static SIMPLE_DEV_PM_OPS(tpm_tis_i2c_ops, tpm_pm_suspend, tpm_pm_resume);

static int tpm_tis_i2c_probe(struct i2c_client *client,
                             const struct i2c_device_id *id)
{
        int rc;
        struct device *dev = &(client->dev);

        if (tpm_dev.client != NULL) {
                dev_err(dev, "This driver only supports one client at a time\n");
                return -EBUSY;  /* We only support one client */
        }

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
                dev_err(dev, "no algorithms associated to the i2c bus\n");
                return -ENODEV;
        }

        tpm_dev.client = client;
        rc = tpm_tis_i2c_init(&client->dev);
        if (rc != 0) {
                tpm_dev.client = NULL;
                rc = -ENODEV;
        }
        return rc;
}

static int tpm_tis_i2c_remove(struct i2c_client *client)
{
        struct tpm_chip *chip = tpm_dev.chip;

        tpm_chip_unregister(chip);
        release_locality(chip, tpm_dev.locality, 1);
        tpm_dev.client = NULL;

        return 0;
}

static struct i2c_driver tpm_tis_i2c_driver = {
        .id_table = tpm_tis_i2c_table,
        .probe = tpm_tis_i2c_probe,
        .remove = tpm_tis_i2c_remove,
        .driver = {
                   .name = "tpm_i2c_infineon",
                   .pm = &tpm_tis_i2c_ops,
                   .of_match_table = of_match_ptr(tpm_tis_i2c_of_match),
                   },
};

module_i2c_driver(tpm_tis_i2c_driver);
MODULE_AUTHOR("Peter Huewe <peter.huewe@infineon.com>");
MODULE_DESCRIPTION("TPM TIS I2C Infineon Driver");
MODULE_VERSION("2.2.0");
MODULE_LICENSE("GPL");