/******************************************************************************
 * Nuvoton TPM I2C Device Driver Interface for WPCT301/NPCT501,
 * based on the TCG TPM Interface Spec version 1.2.
 * Specifications at www.trustedcomputinggroup.org
 *
 * Copyright (C) 2011, Nuvoton Technology Corporation.
 *  Dan Morav <dan.morav@nuvoton.com>
 * Copyright (C) 2013, Obsidian Research Corp.
 *  Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
 *
 * 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/>.
 *
 * Nuvoton contact information: APC.Support@nuvoton.com
 *****************************************************************************/

#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/i2c.h>
#include "tpm.h"

/* I2C interface offsets */
#define TPM_STS                0x00
#define TPM_BURST_COUNT        0x01
#define TPM_DATA_FIFO_W        0x20
#define TPM_DATA_FIFO_R        0x40
#define TPM_VID_DID_RID        0x60
/* TPM command header size */
#define TPM_HEADER_SIZE        10
#define TPM_RETRY      5
/*
 * I2C bus device maximum buffer size w/o counting I2C address or command
 * i.e. max size required for I2C write is 34 = addr, command, 32 bytes data
 */
#define TPM_I2C_MAX_BUF_SIZE           32
#define TPM_I2C_RETRY_COUNT            32
#define TPM_I2C_BUS_DELAY              1       /* msec */
#define TPM_I2C_RETRY_DELAY_SHORT      2       /* msec */
#define TPM_I2C_RETRY_DELAY_LONG       10      /* msec */

#define I2C_DRIVER_NAME "tpm_i2c_nuvoton"

struct priv_data {
        unsigned int intrs;
};

static s32 i2c_nuvoton_read_buf(struct i2c_client *client, u8 offset, u8 size,
                                u8 *data)
{
        s32 status;

        status = i2c_smbus_read_i2c_block_data(client, offset, size, data);
        dev_dbg(&client->dev,
                "%s(offset=%u size=%u data=%*ph) -> sts=%d\n", __func__,
                offset, size, (int)size, data, status);
        return status;
}

static s32 i2c_nuvoton_write_buf(struct i2c_client *client, u8 offset, u8 size,
                                 u8 *data)
{
        s32 status;

        status = i2c_smbus_write_i2c_block_data(client, offset, size, data);
        dev_dbg(&client->dev,
                "%s(offset=%u size=%u data=%*ph) -> sts=%d\n", __func__,
                offset, size, (int)size, data, status);
        return status;
}

#define TPM_STS_VALID          0x80
#define TPM_STS_COMMAND_READY  0x40
#define TPM_STS_GO             0x20
#define TPM_STS_DATA_AVAIL     0x10
#define TPM_STS_EXPECT         0x08
#define TPM_STS_RESPONSE_RETRY 0x02
#define TPM_STS_ERR_VAL        0x07    /* bit2...bit0 reads always 0 */

#define TPM_I2C_SHORT_TIMEOUT  750     /* ms */
#define TPM_I2C_LONG_TIMEOUT   2000    /* 2 sec */

/* read TPM_STS register */
static u8 i2c_nuvoton_read_status(struct tpm_chip *chip)
{
        struct i2c_client *client = to_i2c_client(chip->pdev);
        s32 status;
        u8 data;

        status = i2c_nuvoton_read_buf(client, TPM_STS, 1, &data);
        if (status <= 0) {
                dev_err(chip->pdev, "%s() error return %d\n", __func__,
                        status);
                data = TPM_STS_ERR_VAL;
        }

        return data;
}

/* write byte to TPM_STS register */
static s32 i2c_nuvoton_write_status(struct i2c_client *client, u8 data)
{
        s32 status;
        int i;

        /* this causes the current command to be aborted */
        for (i = 0, status = -1; i < TPM_I2C_RETRY_COUNT && status < 0; i++) {
                status = i2c_nuvoton_write_buf(client, TPM_STS, 1, &data);
                msleep(TPM_I2C_BUS_DELAY);
        }
        return status;
}

/* write commandReady to TPM_STS register */
static void i2c_nuvoton_ready(struct tpm_chip *chip)
{
        struct i2c_client *client = to_i2c_client(chip->pdev);
        s32 status;

        /* this causes the current command to be aborted */
        status = i2c_nuvoton_write_status(client, TPM_STS_COMMAND_READY);
        if (status < 0)
                dev_err(chip->pdev,
                        "%s() fail to write TPM_STS.commandReady\n", __func__);
}

/* read burstCount field from TPM_STS register
 * return -1 on fail to read */
static int i2c_nuvoton_get_burstcount(struct i2c_client *client,
                                      struct tpm_chip *chip)
{
        unsigned long stop = jiffies + chip->vendor.timeout_d;
        s32 status;
        int burst_count = -1;
        u8 data;

        /* wait for burstcount to be non-zero */
        do {
                /* in I2C burstCount is 1 byte */
                status = i2c_nuvoton_read_buf(client, TPM_BURST_COUNT, 1,
                                              &data);
                if (status > 0 && data > 0) {
                        burst_count = min_t(u8, TPM_I2C_MAX_BUF_SIZE, data);
                        break;
                }
                msleep(TPM_I2C_BUS_DELAY);
        } while (time_before(jiffies, stop));

        return burst_count;
}

/*
 * WPCT301/NPCT501 SINT# supports only dataAvail
 * any call to this function which is not waiting for dataAvail will
 * set queue to NULL to avoid waiting for interrupt
 */
static bool i2c_nuvoton_check_status(struct tpm_chip *chip, u8 mask, u8 value)
{
        u8 status = i2c_nuvoton_read_status(chip);
        return (status != TPM_STS_ERR_VAL) && ((status & mask) == value);
}

static int i2c_nuvoton_wait_for_stat(struct tpm_chip *chip, u8 mask, u8 value,
                                     u32 timeout, wait_queue_head_t *queue)
{
        if (chip->vendor.irq && queue) {
                s32 rc;
                struct priv_data *priv = chip->vendor.priv;
                unsigned int cur_intrs = priv->intrs;

                enable_irq(chip->vendor.irq);
                rc = wait_event_interruptible_timeout(*queue,
                                                      cur_intrs != priv->intrs,
                                                      timeout);
                if (rc > 0)
                        return 0;
                /* At this point we know that the SINT pin is asserted, so we
                 * do not need to do i2c_nuvoton_check_status */
        } else {
                unsigned long ten_msec, stop;
                bool status_valid;

                /* check current status */
                status_valid = i2c_nuvoton_check_status(chip, mask, value);
                if (status_valid)
                        return 0;

                /* use polling to wait for the event */
                ten_msec = jiffies + msecs_to_jiffies(TPM_I2C_RETRY_DELAY_LONG);
                stop = jiffies + timeout;
                do {
                        if (time_before(jiffies, ten_msec))
                                msleep(TPM_I2C_RETRY_DELAY_SHORT);
                        else
                                msleep(TPM_I2C_RETRY_DELAY_LONG);
                        status_valid = i2c_nuvoton_check_status(chip, mask,
                                                                value);
                        if (status_valid)
                                return 0;
                } while (time_before(jiffies, stop));
        }
        dev_err(chip->pdev, "%s(%02x, %02x) -> timeout\n", __func__, mask,
                value);
        return -ETIMEDOUT;
}

/* wait for dataAvail field to be set in the TPM_STS register */
static int i2c_nuvoton_wait_for_data_avail(struct tpm_chip *chip, u32 timeout,
                                           wait_queue_head_t *queue)
{
        return i2c_nuvoton_wait_for_stat(chip,
                                         TPM_STS_DATA_AVAIL | TPM_STS_VALID,
                                         TPM_STS_DATA_AVAIL | TPM_STS_VALID,
                                         timeout, queue);
}

/* Read @count bytes into @buf from TPM_RD_FIFO register */
static int i2c_nuvoton_recv_data(struct i2c_client *client,
                                 struct tpm_chip *chip, u8 *buf, size_t count)
{
        s32 rc;
        int burst_count, bytes2read, size = 0;

        while (size < count &&
               i2c_nuvoton_wait_for_data_avail(chip,
                                               chip->vendor.timeout_c,
                                               &chip->vendor.read_queue) == 0) {
                burst_count = i2c_nuvoton_get_burstcount(client, chip);
                if (burst_count < 0) {
                        dev_err(chip->pdev,
                                "%s() fail to read burstCount=%d\n", __func__,
                                burst_count);
                        return -EIO;
                }
                bytes2read = min_t(size_t, burst_count, count - size);
                rc = i2c_nuvoton_read_buf(client, TPM_DATA_FIFO_R,
                                          bytes2read, &buf[size]);
                if (rc < 0) {
                        dev_err(chip->pdev,
                                "%s() fail on i2c_nuvoton_read_buf()=%d\n",
                                __func__, rc);
                        return -EIO;
                }
                dev_dbg(chip->pdev, "%s(%d):", __func__, bytes2read);
                size += bytes2read;
        }

        return size;
}

/* Read TPM command results */
static int i2c_nuvoton_recv(struct tpm_chip *chip, u8 *buf, size_t count)
{
        struct device *dev = chip->pdev;
        struct i2c_client *client = to_i2c_client(dev);
        s32 rc;
        int expected, status, burst_count, retries, size = 0;

        if (count < TPM_HEADER_SIZE) {
                i2c_nuvoton_ready(chip);    /* return to idle */
                dev_err(dev, "%s() count < header size\n", __func__);
                return -EIO;
        }
        for (retries = 0; retries < TPM_RETRY; retries++) {
                if (retries > 0) {
                        /* if this is not the first trial, set responseRetry */
                        i2c_nuvoton_write_status(client,
                                                 TPM_STS_RESPONSE_RETRY);
                }
                /*
                 * read first available (> 10 bytes), including:
                 * tag, paramsize, and result
                 */
                status = i2c_nuvoton_wait_for_data_avail(
                        chip, chip->vendor.timeout_c, &chip->vendor.read_queue);
                if (status != 0) {
                        dev_err(dev, "%s() timeout on dataAvail\n", __func__);
                        size = -ETIMEDOUT;
                        continue;
                }
                burst_count = i2c_nuvoton_get_burstcount(client, chip);
                if (burst_count < 0) {
                        dev_err(dev, "%s() fail to get burstCount\n", __func__);
                        size = -EIO;
                        continue;
                }
                size = i2c_nuvoton_recv_data(client, chip, buf,
                                             burst_count);
                if (size < TPM_HEADER_SIZE) {
                        dev_err(dev, "%s() fail to read header\n", __func__);
                        size = -EIO;
                        continue;
                }
                /*
                 * convert number of expected bytes field from big endian 32 bit
                 * to machine native
                 */
                expected = be32_to_cpu(*(__be32 *) (buf + 2));
                if (expected > count) {
                        dev_err(dev, "%s() expected > count\n", __func__);
                        size = -EIO;
                        continue;
                }
                rc = i2c_nuvoton_recv_data(client, chip, &buf[size],
                                           expected - size);
                size += rc;
                if (rc < 0 || size < expected) {
                        dev_err(dev, "%s() fail to read remainder of result\n",
                                __func__);
                        size = -EIO;
                        continue;
                }
                if (i2c_nuvoton_wait_for_stat(
                            chip, TPM_STS_VALID | TPM_STS_DATA_AVAIL,
                            TPM_STS_VALID, chip->vendor.timeout_c,
                            NULL)) {
                        dev_err(dev, "%s() error left over data\n", __func__);
                        size = -ETIMEDOUT;
                        continue;
                }
                break;
        }
        i2c_nuvoton_ready(chip);
        dev_dbg(chip->pdev, "%s() -> %d\n", __func__, size);
        return size;
}

/*
 * Send TPM command.
 *
 * If interrupts are used (signaled by an irq set in the vendor structure)
 * tpm.c can skip polling for the data to be available as the interrupt is
 * waited for here
 */
static int i2c_nuvoton_send(struct tpm_chip *chip, u8 *buf, size_t len)
{
        struct device *dev = chip->pdev;
        struct i2c_client *client = to_i2c_client(dev);
        u32 ordinal;
        size_t count = 0;
        int burst_count, bytes2write, retries, rc = -EIO;

        for (retries = 0; retries < TPM_RETRY; retries++) {
                i2c_nuvoton_ready(chip);
                if (i2c_nuvoton_wait_for_stat(chip, TPM_STS_COMMAND_READY,
                                              TPM_STS_COMMAND_READY,
                                              chip->vendor.timeout_b, NULL)) {
                        dev_err(dev, "%s() timeout on commandReady\n",
                                __func__);
                        rc = -EIO;
                        continue;
                }
                rc = 0;
                while (count < len - 1) {
                        burst_count = i2c_nuvoton_get_burstcount(client,
                                                                 chip);
                        if (burst_count < 0) {
                                dev_err(dev, "%s() fail get burstCount\n",
                                        __func__);
                                rc = -EIO;
                                break;
                        }
                        bytes2write = min_t(size_t, burst_count,
                                            len - 1 - count);
                        rc = i2c_nuvoton_write_buf(client, TPM_DATA_FIFO_W,
                                                   bytes2write, &buf[count]);
                        if (rc < 0) {
                                dev_err(dev, "%s() fail i2cWriteBuf\n",
                                        __func__);
                                break;
                        }
                        dev_dbg(dev, "%s(%d):", __func__, bytes2write);
                        count += bytes2write;
                        rc = i2c_nuvoton_wait_for_stat(chip,
                                                       TPM_STS_VALID |
                                                       TPM_STS_EXPECT,
                                                       TPM_STS_VALID |
                                                       TPM_STS_EXPECT,
                                                       chip->vendor.timeout_c,
                                                       NULL);
                        if (rc < 0) {
                                dev_err(dev, "%s() timeout on Expect\n",
                                        __func__);
                                rc = -ETIMEDOUT;
                                break;
                        }
                }
                if (rc < 0)
                        continue;

                /* write last byte */
                rc = i2c_nuvoton_write_buf(client, TPM_DATA_FIFO_W, 1,
                                           &buf[count]);
                if (rc < 0) {
                        dev_err(dev, "%s() fail to write last byte\n",
                                __func__);
                        rc = -EIO;
                        continue;
                }
                dev_dbg(dev, "%s(last): %02x", __func__, buf[count]);
                rc = i2c_nuvoton_wait_for_stat(chip,
                                               TPM_STS_VALID | TPM_STS_EXPECT,
                                               TPM_STS_VALID,
                                               chip->vendor.timeout_c, NULL);
                if (rc) {
                        dev_err(dev, "%s() timeout on Expect to clear\n",
                                __func__);
                        rc = -ETIMEDOUT;
                        continue;
                }
                break;
        }
        if (rc < 0) {
                /* retries == TPM_RETRY */
                i2c_nuvoton_ready(chip);
                return rc;
        }
        /* execute the TPM command */
        rc = i2c_nuvoton_write_status(client, TPM_STS_GO);
        if (rc < 0) {
                dev_err(dev, "%s() fail to write Go\n", __func__);
                i2c_nuvoton_ready(chip);
                return rc;
        }
        ordinal = be32_to_cpu(*((__be32 *) (buf + 6)));
        rc = i2c_nuvoton_wait_for_data_avail(chip,
                                             tpm_calc_ordinal_duration(chip,
                                                                       ordinal),
                                             &chip->vendor.read_queue);
        if (rc) {
                dev_err(dev, "%s() timeout command duration\n", __func__);
                i2c_nuvoton_ready(chip);
                return rc;
        }

        dev_dbg(dev, "%s() -> %zd\n", __func__, len);
        return len;
}

static bool i2c_nuvoton_req_canceled(struct tpm_chip *chip, u8 status)
{
        return (status == TPM_STS_COMMAND_READY);
}

static const struct tpm_class_ops tpm_i2c = {
        .status = i2c_nuvoton_read_status,
        .recv = i2c_nuvoton_recv,
        .send = i2c_nuvoton_send,
        .cancel = i2c_nuvoton_ready,
        .req_complete_mask = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
        .req_complete_val = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
        .req_canceled = i2c_nuvoton_req_canceled,
};

/* The only purpose for the handler is to signal to any waiting threads that
 * the interrupt is currently being asserted. The driver does not do any
 * processing triggered by interrupts, and the chip provides no way to mask at
 * the source (plus that would be slow over I2C). Run the IRQ as a one-shot,
 * this means it cannot be shared. */
static irqreturn_t i2c_nuvoton_int_handler(int dummy, void *dev_id)
{
        struct tpm_chip *chip = dev_id;
        struct priv_data *priv = chip->vendor.priv;

        priv->intrs++;
        wake_up(&chip->vendor.read_queue);
        disable_irq_nosync(chip->vendor.irq);
        return IRQ_HANDLED;
}

static int get_vid(struct i2c_client *client, u32 *res)
{
        static const u8 vid_did_rid_value[] = { 0x50, 0x10, 0xfe };
        u32 temp;
        s32 rc;

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
                return -ENODEV;
        rc = i2c_nuvoton_read_buf(client, TPM_VID_DID_RID, 4, (u8 *)&temp);
        if (rc < 0)
                return rc;

        /* check WPCT301 values - ignore RID */
        if (memcmp(&temp, vid_did_rid_value, sizeof(vid_did_rid_value))) {
                /*
                 * f/w rev 2.81 has an issue where the VID_DID_RID is not
                 * reporting the right value. so give it another chance at
                 * offset 0x20 (FIFO_W).
                 */
                rc = i2c_nuvoton_read_buf(client, TPM_DATA_FIFO_W, 4,
                                          (u8 *) (&temp));
                if (rc < 0)
                        return rc;

                /* check WPCT301 values - ignore RID */
                if (memcmp(&temp, vid_did_rid_value,
                           sizeof(vid_did_rid_value)))
                        return -ENODEV;
        }

        *res = temp;
        return 0;
}

static int i2c_nuvoton_probe(struct i2c_client *client,
                             const struct i2c_device_id *id)
{
        int rc;
        struct tpm_chip *chip;
        struct device *dev = &client->dev;
        u32 vid = 0;

        rc = get_vid(client, &vid);
        if (rc)
                return rc;

        dev_info(dev, "VID: %04X DID: %02X RID: %02X\n", (u16) vid,
                 (u8) (vid >> 16), (u8) (vid >> 24));

        chip = tpmm_chip_alloc(dev, &tpm_i2c);
        if (IS_ERR(chip))
                return PTR_ERR(chip);

        chip->vendor.priv = devm_kzalloc(dev, sizeof(struct priv_data),
                                         GFP_KERNEL);
        if (!chip->vendor.priv)
                return -ENOMEM;

        init_waitqueue_head(&chip->vendor.read_queue);
        init_waitqueue_head(&chip->vendor.int_queue);

        /* Default timeouts */
        chip->vendor.timeout_a = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
        chip->vendor.timeout_b = msecs_to_jiffies(TPM_I2C_LONG_TIMEOUT);
        chip->vendor.timeout_c = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);
        chip->vendor.timeout_d = msecs_to_jiffies(TPM_I2C_SHORT_TIMEOUT);

        /*
         * I2C intfcaps (interrupt capabilitieis) in the chip are hard coded to:
         *   TPM_INTF_INT_LEVEL_LOW | TPM_INTF_DATA_AVAIL_INT
         * The IRQ should be set in the i2c_board_info (which is done
         * automatically in of_i2c_register_devices, for device tree users */
        chip->vendor.irq = client->irq;

        if (chip->vendor.irq) {
                dev_dbg(dev, "%s() chip-vendor.irq\n", __func__);
                rc = devm_request_irq(dev, chip->vendor.irq,
                                      i2c_nuvoton_int_handler,
                                      IRQF_TRIGGER_LOW,
                                      chip->devname,
                                      chip);
                if (rc) {
                        dev_err(dev, "%s() Unable to request irq: %d for use\n",
                                __func__, chip->vendor.irq);
                        chip->vendor.irq = 0;
                } else {
                        /* Clear any pending interrupt */
                        i2c_nuvoton_ready(chip);
                        /* - wait for TPM_STS==0xA0 (stsValid, commandReady) */
                        rc = i2c_nuvoton_wait_for_stat(chip,
                                                       TPM_STS_COMMAND_READY,
                                                       TPM_STS_COMMAND_READY,
                                                       chip->vendor.timeout_b,
                                                       NULL);
                        if (rc == 0) {
                                /*
                                 * TIS is in ready state
                                 * write dummy byte to enter reception state
                                 * TPM_DATA_FIFO_W <- rc (0)
                                 */
                                rc = i2c_nuvoton_write_buf(client,
                                                           TPM_DATA_FIFO_W,
                                                           1, (u8 *) (&rc));
                                if (rc < 0)
                                        return rc;
                                /* TPM_STS <- 0x40 (commandReady) */
                                i2c_nuvoton_ready(chip);
                        } else {
                                /*
                                 * timeout_b reached - command was
                                 * aborted. TIS should now be in idle state -
                                 * only TPM_STS_VALID should be set
                                 */
                                if (i2c_nuvoton_read_status(chip) !=
                                    TPM_STS_VALID)
                                        return -EIO;
                        }
                }
        }

        if (tpm_get_timeouts(chip))
                return -ENODEV;

        if (tpm_do_selftest(chip))
                return -ENODEV;

        return tpm_chip_register(chip);
}

static int i2c_nuvoton_remove(struct i2c_client *client)
{
        struct device *dev = &(client->dev);
        struct tpm_chip *chip = dev_get_drvdata(dev);
        tpm_chip_unregister(chip);
        return 0;
}

static const struct i2c_device_id i2c_nuvoton_id[] = {
        {I2C_DRIVER_NAME, 0},
        {}
};
MODULE_DEVICE_TABLE(i2c, i2c_nuvoton_id);

#ifdef CONFIG_OF
static const struct of_device_id i2c_nuvoton_of_match[] = {
        {.compatible = "nuvoton,npct501"},
        {.compatible = "winbond,wpct301"},
        {},
};
MODULE_DEVICE_TABLE(of, i2c_nuvoton_of_match);
#endif

static SIMPLE_DEV_PM_OPS(i2c_nuvoton_pm_ops, tpm_pm_suspend, tpm_pm_resume);

static struct i2c_driver i2c_nuvoton_driver = {
        .id_table = i2c_nuvoton_id,
        .probe = i2c_nuvoton_probe,
        .remove = i2c_nuvoton_remove,
        .driver = {
                .name = I2C_DRIVER_NAME,
                .pm = &i2c_nuvoton_pm_ops,
                .of_match_table = of_match_ptr(i2c_nuvoton_of_match),
        },
};

module_i2c_driver(i2c_nuvoton_driver);

MODULE_AUTHOR("Dan Morav (dan.morav@nuvoton.com)");
MODULE_DESCRIPTION("Nuvoton TPM I2C Driver");
MODULE_LICENSE("GPL");