/*
 * ATMEL I2C TPM AT97SC3204T
 *
 * Copyright (C) 2012 V Lab Technologies
 *  Teddy Reed <teddy@prosauce.org>
 * Copyright (C) 2013, Obsidian Research Corp.
 *  Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
 * Device driver for ATMEL I2C TPMs.
 *
 * Teddy Reed determined the basic I2C command flow, unlike other I2C TPM
 * devices the raw TCG formatted TPM command data is written via I2C and then
 * raw TCG formatted TPM command data is returned via I2C.
 *
 * TGC status/locality/etc functions seen in the LPC implementation do not
 * seem to be present.
 *
 * 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/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include "tpm.h"

#define I2C_DRIVER_NAME "tpm_i2c_atmel"

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

#define ATMEL_STS_OK 1

struct priv_data {
        size_t len;
        /* This is the amount we read on the first try. 25 was chosen to fit a
         * fair number of read responses in the buffer so a 2nd retry can be
         * avoided in small message cases. */
        u8 buffer[sizeof(struct tpm_output_header) + 25];
};

static int i2c_atmel_send(struct tpm_chip *chip, u8 *buf, size_t len)
{
        struct priv_data *priv = chip->vendor.priv;
        struct i2c_client *client = to_i2c_client(chip->pdev);
        s32 status;

        priv->len = 0;

        if (len <= 2)
                return -EIO;

        status = i2c_master_send(client, buf, len);

        dev_dbg(chip->pdev,
                "%s(buf=%*ph len=%0zx) -> sts=%d\n", __func__,
                (int)min_t(size_t, 64, len), buf, len, status);
        return status;
}

static int i2c_atmel_recv(struct tpm_chip *chip, u8 *buf, size_t count)
{
        struct priv_data *priv = chip->vendor.priv;
        struct i2c_client *client = to_i2c_client(chip->pdev);
        struct tpm_output_header *hdr =
                (struct tpm_output_header *)priv->buffer;
        u32 expected_len;
        int rc;

        if (priv->len == 0)
                return -EIO;

        /* Get the message size from the message header, if we didn't get the
         * whole message in read_status then we need to re-read the
         * message. */
        expected_len = be32_to_cpu(hdr->length);
        if (expected_len > count)
                return -ENOMEM;

        if (priv->len >= expected_len) {
                dev_dbg(chip->pdev,
                        "%s early(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
                        (int)min_t(size_t, 64, expected_len), buf, count,
                        expected_len);
                memcpy(buf, priv->buffer, expected_len);
                return expected_len;
        }

        rc = i2c_master_recv(client, buf, expected_len);
        dev_dbg(chip->pdev,
                "%s reread(buf=%*ph count=%0zx) -> ret=%d\n", __func__,
                (int)min_t(size_t, 64, expected_len), buf, count,
                expected_len);
        return rc;
}

static void i2c_atmel_cancel(struct tpm_chip *chip)
{
        dev_err(chip->pdev, "TPM operation cancellation was requested, but is not supported");
}

static u8 i2c_atmel_read_status(struct tpm_chip *chip)
{
        struct priv_data *priv = chip->vendor.priv;
        struct i2c_client *client = to_i2c_client(chip->pdev);
        int rc;

        /* The TPM fails the I2C read until it is ready, so we do the entire
         * transfer here and buffer it locally. This way the common code can
         * properly handle the timeouts. */
        priv->len = 0;
        memset(priv->buffer, 0, sizeof(priv->buffer));


        /* Once the TPM has completed the command the command remains readable
         * until another command is issued. */
        rc = i2c_master_recv(client, priv->buffer, sizeof(priv->buffer));
        dev_dbg(chip->pdev,
                "%s: sts=%d", __func__, rc);
        if (rc <= 0)
                return 0;

        priv->len = rc;

        return ATMEL_STS_OK;
}

static bool i2c_atmel_req_canceled(struct tpm_chip *chip, u8 status)
{
        return false;
}

static const struct tpm_class_ops i2c_atmel = {
        .status = i2c_atmel_read_status,
        .recv = i2c_atmel_recv,
        .send = i2c_atmel_send,
        .cancel = i2c_atmel_cancel,
        .req_complete_mask = ATMEL_STS_OK,
        .req_complete_val = ATMEL_STS_OK,
        .req_canceled = i2c_atmel_req_canceled,
};

static int i2c_atmel_probe(struct i2c_client *client,
                           const struct i2c_device_id *id)
{
        struct tpm_chip *chip;
        struct device *dev = &client->dev;

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
                return -ENODEV;

        chip = tpmm_chip_alloc(dev, &i2c_atmel);
        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;

        /* 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);
        chip->vendor.irq = 0;

        /* There is no known way to probe for this device, and all version
         * information seems to be read via TPM commands. Thus we rely on the
         * TPM startup process in the common code to detect the device. */
        if (tpm_get_timeouts(chip))
                return -ENODEV;

        if (tpm_do_selftest(chip))
                return -ENODEV;

        return tpm_chip_register(chip);
}

static int i2c_atmel_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_atmel_id[] = {
        {I2C_DRIVER_NAME, 0},
        {}
};
MODULE_DEVICE_TABLE(i2c, i2c_atmel_id);

#ifdef CONFIG_OF
static const struct of_device_id i2c_atmel_of_match[] = {
        {.compatible = "atmel,at97sc3204t"},
        {},
};
MODULE_DEVICE_TABLE(of, i2c_atmel_of_match);
#endif

static SIMPLE_DEV_PM_OPS(i2c_atmel_pm_ops, tpm_pm_suspend, tpm_pm_resume);

static struct i2c_driver i2c_atmel_driver = {
        .id_table = i2c_atmel_id,
        .probe = i2c_atmel_probe,
        .remove = i2c_atmel_remove,
        .driver = {
                .name = I2C_DRIVER_NAME,
                .pm = &i2c_atmel_pm_ops,
                .of_match_table = of_match_ptr(i2c_atmel_of_match),
        },
};

module_i2c_driver(i2c_atmel_driver);

MODULE_AUTHOR("Jason Gunthorpe <jgunthorpe@obsidianresearch.com>");
MODULE_DESCRIPTION("Atmel TPM I2C Driver");
MODULE_LICENSE("GPL");