Linux 4.19.133

[linux/fpc-iii.git] / drivers / char / tpm / tpm_ibmvtpm.c

/*
 * Copyright (C) 2012-2020 IBM Corporation
 *
 * Author: Ashley Lai <ashleydlai@gmail.com>
 *
 * Maintained by: <tpmdd-devel@lists.sourceforge.net>
 *
 * Device driver for TCG/TCPA TPM (trusted platform module).
 * Specifications at www.trustedcomputinggroup.org
 *
 * 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/dma-mapping.h>
#include <linux/dmapool.h>
#include <linux/slab.h>
#include <asm/vio.h>
#include <asm/irq.h>
#include <linux/types.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/wait.h>
#include <asm/prom.h>

#include "tpm.h"
#include "tpm_ibmvtpm.h"

static const char tpm_ibmvtpm_driver_name[] = "tpm_ibmvtpm";

static const struct vio_device_id tpm_ibmvtpm_device_table[] = {
        { "IBM,vtpm", "IBM,vtpm"},
        { "", "" }
};
MODULE_DEVICE_TABLE(vio, tpm_ibmvtpm_device_table);

/**
 *
 * ibmvtpm_send_crq_word - Send a CRQ request
 * @vdev:       vio device struct
 * @w1:         pre-constructed first word of tpm crq (second word is reserved)
 *
 * Return:
 *      0 - Success
 *      Non-zero - Failure
 */
static int ibmvtpm_send_crq_word(struct vio_dev *vdev, u64 w1)
{
        return plpar_hcall_norets(H_SEND_CRQ, vdev->unit_address, w1, 0);
}

/**
 *
 * ibmvtpm_send_crq - Send a CRQ request
 *
 * @vdev:       vio device struct
 * @valid:      Valid field
 * @msg:        Type field
 * @len:        Length field
 * @data:       Data field
 *
 * The ibmvtpm crq is defined as follows:
 *
 * Byte  |   0   |   1   |   2   |   3   |   4   |   5   |   6   |   7
 * -----------------------------------------------------------------------
 * Word0 | Valid | Type  |     Length    |              Data
 * -----------------------------------------------------------------------
 * Word1 |                Reserved
 * -----------------------------------------------------------------------
 *
 * Which matches the following structure (on bigendian host):
 *
 * struct ibmvtpm_crq {
 *         u8 valid;
 *         u8 msg;
 *         __be16 len;
 *         __be32 data;
 *         __be64 reserved;
 * } __attribute__((packed, aligned(8)));
 *
 * However, the value is passed in a register so just compute the numeric value
 * to load into the register avoiding byteswap altogether. Endian only affects
 * memory loads and stores - registers are internally represented the same.
 *
 * Return:
 *      0 (H_SUCCESS) - Success
 *      Non-zero - Failure
 */
static int ibmvtpm_send_crq(struct vio_dev *vdev,
                u8 valid, u8 msg, u16 len, u32 data)
{
        u64 w1 = ((u64)valid << 56) | ((u64)msg << 48) | ((u64)len << 32) |
                (u64)data;
        return ibmvtpm_send_crq_word(vdev, w1);
}

/**
 * tpm_ibmvtpm_recv - Receive data after send
 *
 * @chip:       tpm chip struct
 * @buf:        buffer to read
 * @count:      size of buffer
 *
 * Return:
 *      Number of bytes read
 */
static int tpm_ibmvtpm_recv(struct tpm_chip *chip, u8 *buf, size_t count)
{
        struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
        u16 len;
        int sig;

        if (!ibmvtpm->rtce_buf) {
                dev_err(ibmvtpm->dev, "ibmvtpm device is not ready\n");
                return 0;
        }

        sig = wait_event_interruptible(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
        if (sig)
                return -EINTR;

        len = ibmvtpm->res_len;

        if (count < len) {
                dev_err(ibmvtpm->dev,
                        "Invalid size in recv: count=%zd, crq_size=%d\n",
                        count, len);
                return -EIO;
        }

        spin_lock(&ibmvtpm->rtce_lock);
        memcpy((void *)buf, (void *)ibmvtpm->rtce_buf, len);
        memset(ibmvtpm->rtce_buf, 0, len);
        ibmvtpm->res_len = 0;
        spin_unlock(&ibmvtpm->rtce_lock);
        return len;
}

/**
 * ibmvtpm_crq_send_init - Send a CRQ initialize message
 * @ibmvtpm:    vtpm device struct
 *
 * Return:
 *      0 on success.
 *      Non-zero on failure.
 */
static int ibmvtpm_crq_send_init(struct ibmvtpm_dev *ibmvtpm)
{
        int rc;

        rc = ibmvtpm_send_crq_word(ibmvtpm->vdev, INIT_CRQ_CMD);
        if (rc != H_SUCCESS)
                dev_err(ibmvtpm->dev,
                        "%s failed rc=%d\n", __func__, rc);

        return rc;
}

/**
 * tpm_ibmvtpm_resume - Resume from suspend
 *
 * @dev:        device struct
 *
 * Return: Always 0.
 */
static int tpm_ibmvtpm_resume(struct device *dev)
{
        struct tpm_chip *chip = dev_get_drvdata(dev);
        struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
        int rc = 0;

        do {
                if (rc)
                        msleep(100);
                rc = plpar_hcall_norets(H_ENABLE_CRQ,
                                        ibmvtpm->vdev->unit_address);
        } while (rc == H_IN_PROGRESS || rc == H_BUSY || H_IS_LONG_BUSY(rc));

        if (rc) {
                dev_err(dev, "Error enabling ibmvtpm rc=%d\n", rc);
                return rc;
        }

        rc = vio_enable_interrupts(ibmvtpm->vdev);
        if (rc) {
                dev_err(dev, "Error vio_enable_interrupts rc=%d\n", rc);
                return rc;
        }

        rc = ibmvtpm_crq_send_init(ibmvtpm);
        if (rc)
                dev_err(dev, "Error send_init rc=%d\n", rc);

        return rc;
}

/**
 * tpm_ibmvtpm_send() - Send a TPM command
 * @chip:       tpm chip struct
 * @buf:        buffer contains data to send
 * @count:      size of buffer
 *
 * Return:
 *   0 on success,
 *   -errno on error
 */
static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
{
        struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
        bool retry = true;
        int rc, sig;

        if (!ibmvtpm->rtce_buf) {
                dev_err(ibmvtpm->dev, "ibmvtpm device is not ready\n");
                return 0;
        }

        if (count > ibmvtpm->rtce_size) {
                dev_err(ibmvtpm->dev,
                        "Invalid size in send: count=%zd, rtce_size=%d\n",
                        count, ibmvtpm->rtce_size);
                return -EIO;
        }

        if (ibmvtpm->tpm_processing_cmd) {
                dev_info(ibmvtpm->dev,
                         "Need to wait for TPM to finish\n");
                /* wait for previous command to finish */
                sig = wait_event_interruptible(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
                if (sig)
                        return -EINTR;
        }

        spin_lock(&ibmvtpm->rtce_lock);
        ibmvtpm->res_len = 0;
        memcpy((void *)ibmvtpm->rtce_buf, (void *)buf, count);

        /*
         * set the processing flag before the Hcall, since we may get the
         * result (interrupt) before even being able to check rc.
         */
        ibmvtpm->tpm_processing_cmd = true;

again:
        rc = ibmvtpm_send_crq(ibmvtpm->vdev,
                        IBMVTPM_VALID_CMD, VTPM_TPM_COMMAND,
                        count, ibmvtpm->rtce_dma_handle);
        if (rc != H_SUCCESS) {
                /*
                 * H_CLOSED can be returned after LPM resume.  Call
                 * tpm_ibmvtpm_resume() to re-enable the CRQ then retry
                 * ibmvtpm_send_crq() once before failing.
                 */
                if (rc == H_CLOSED && retry) {
                        tpm_ibmvtpm_resume(ibmvtpm->dev);
                        retry = false;
                        goto again;
                }
                dev_err(ibmvtpm->dev, "tpm_ibmvtpm_send failed rc=%d\n", rc);
                ibmvtpm->tpm_processing_cmd = false;
        }

        spin_unlock(&ibmvtpm->rtce_lock);
        return 0;
}

static void tpm_ibmvtpm_cancel(struct tpm_chip *chip)
{
        return;
}

static u8 tpm_ibmvtpm_status(struct tpm_chip *chip)
{
        return 0;
}

/**
 * ibmvtpm_crq_get_rtce_size - Send a CRQ request to get rtce size
 *
 * @ibmvtpm:    vtpm device struct
 *
 * Return:
 *      0 on success.
 *      Non-zero on failure.
 */
static int ibmvtpm_crq_get_rtce_size(struct ibmvtpm_dev *ibmvtpm)
{
        int rc;

        rc = ibmvtpm_send_crq(ibmvtpm->vdev,
                        IBMVTPM_VALID_CMD, VTPM_GET_RTCE_BUFFER_SIZE, 0, 0);
        if (rc != H_SUCCESS)
                dev_err(ibmvtpm->dev,
                        "ibmvtpm_crq_get_rtce_size failed rc=%d\n", rc);

        return rc;
}

/**
 * ibmvtpm_crq_get_version - Send a CRQ request to get vtpm version
 *                         - Note that this is vtpm version and not tpm version
 *
 * @ibmvtpm:    vtpm device struct
 *
 * Return:
 *      0 on success.
 *      Non-zero on failure.
 */
static int ibmvtpm_crq_get_version(struct ibmvtpm_dev *ibmvtpm)
{
        int rc;

        rc = ibmvtpm_send_crq(ibmvtpm->vdev,
                        IBMVTPM_VALID_CMD, VTPM_GET_VERSION, 0, 0);
        if (rc != H_SUCCESS)
                dev_err(ibmvtpm->dev,
                        "ibmvtpm_crq_get_version failed rc=%d\n", rc);

        return rc;
}

/**
 * ibmvtpm_crq_send_init_complete - Send a CRQ initialize complete message
 * @ibmvtpm:    vtpm device struct
 *
 * Return:
 *      0 on success.
 *      Non-zero on failure.
 */
static int ibmvtpm_crq_send_init_complete(struct ibmvtpm_dev *ibmvtpm)
{
        int rc;

        rc = ibmvtpm_send_crq_word(ibmvtpm->vdev, INIT_CRQ_COMP_CMD);
        if (rc != H_SUCCESS)
                dev_err(ibmvtpm->dev,
                        "ibmvtpm_crq_send_init_complete failed rc=%d\n", rc);

        return rc;
}

/**
 * tpm_ibmvtpm_remove - ibm vtpm remove entry point
 * @vdev:       vio device struct
 *
 * Return: Always 0.
 */
static int tpm_ibmvtpm_remove(struct vio_dev *vdev)
{
        struct tpm_chip *chip = dev_get_drvdata(&vdev->dev);
        struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
        int rc = 0;

        tpm_chip_unregister(chip);

        free_irq(vdev->irq, ibmvtpm);

        do {
                if (rc)
                        msleep(100);
                rc = plpar_hcall_norets(H_FREE_CRQ, vdev->unit_address);
        } while (rc == H_BUSY || H_IS_LONG_BUSY(rc));

        dma_unmap_single(ibmvtpm->dev, ibmvtpm->crq_dma_handle,
                         CRQ_RES_BUF_SIZE, DMA_BIDIRECTIONAL);
        free_page((unsigned long)ibmvtpm->crq_queue.crq_addr);

        if (ibmvtpm->rtce_buf) {
                dma_unmap_single(ibmvtpm->dev, ibmvtpm->rtce_dma_handle,
                                 ibmvtpm->rtce_size, DMA_BIDIRECTIONAL);
                kfree(ibmvtpm->rtce_buf);
        }

        kfree(ibmvtpm);
        /* For tpm_ibmvtpm_get_desired_dma */
        dev_set_drvdata(&vdev->dev, NULL);

        return 0;
}

/**
 * tpm_ibmvtpm_get_desired_dma - Get DMA size needed by this driver
 * @vdev:       vio device struct
 *
 * Return:
 *      Number of bytes the driver needs to DMA map.
 */
static unsigned long tpm_ibmvtpm_get_desired_dma(struct vio_dev *vdev)
{
        struct tpm_chip *chip = dev_get_drvdata(&vdev->dev);
        struct ibmvtpm_dev *ibmvtpm;

        /*
         * ibmvtpm initializes at probe time, so the data we are
         * asking for may not be set yet. Estimate that 4K required
         * for TCE-mapped buffer in addition to CRQ.
         */
        if (chip)
                ibmvtpm = dev_get_drvdata(&chip->dev);
        else
                return CRQ_RES_BUF_SIZE + PAGE_SIZE;

        return CRQ_RES_BUF_SIZE + ibmvtpm->rtce_size;
}

/**
 * tpm_ibmvtpm_suspend - Suspend
 * @dev:        device struct
 *
 * Return: Always 0.
 */
static int tpm_ibmvtpm_suspend(struct device *dev)
{
        struct tpm_chip *chip = dev_get_drvdata(dev);
        struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
        int rc = 0;

        rc = ibmvtpm_send_crq(ibmvtpm->vdev,
                        IBMVTPM_VALID_CMD, VTPM_PREPARE_TO_SUSPEND, 0, 0);
        if (rc != H_SUCCESS)
                dev_err(ibmvtpm->dev,
                        "tpm_ibmvtpm_suspend failed rc=%d\n", rc);

        return rc;
}

/**
 * ibmvtpm_reset_crq - Reset CRQ
 *
 * @ibmvtpm:    ibm vtpm struct
 *
 * Return:
 *      0 on success.
 *      Non-zero on failure.
 */
static int ibmvtpm_reset_crq(struct ibmvtpm_dev *ibmvtpm)
{
        int rc = 0;

        do {
                if (rc)
                        msleep(100);
                rc = plpar_hcall_norets(H_FREE_CRQ,
                                        ibmvtpm->vdev->unit_address);
        } while (rc == H_BUSY || H_IS_LONG_BUSY(rc));

        memset(ibmvtpm->crq_queue.crq_addr, 0, CRQ_RES_BUF_SIZE);
        ibmvtpm->crq_queue.index = 0;

        return plpar_hcall_norets(H_REG_CRQ, ibmvtpm->vdev->unit_address,
                                  ibmvtpm->crq_dma_handle, CRQ_RES_BUF_SIZE);
}

static bool tpm_ibmvtpm_req_canceled(struct tpm_chip *chip, u8 status)
{
        return (status == 0);
}

static const struct tpm_class_ops tpm_ibmvtpm = {
        .recv = tpm_ibmvtpm_recv,
        .send = tpm_ibmvtpm_send,
        .cancel = tpm_ibmvtpm_cancel,
        .status = tpm_ibmvtpm_status,
        .req_complete_mask = 0,
        .req_complete_val = 0,
        .req_canceled = tpm_ibmvtpm_req_canceled,
};

static const struct dev_pm_ops tpm_ibmvtpm_pm_ops = {
        .suspend = tpm_ibmvtpm_suspend,
        .resume = tpm_ibmvtpm_resume,
};

/**
 * ibmvtpm_crq_get_next - Get next responded crq
 *
 * @ibmvtpm:    vtpm device struct
 *
 * Return: vtpm crq pointer or NULL.
 */
static struct ibmvtpm_crq *ibmvtpm_crq_get_next(struct ibmvtpm_dev *ibmvtpm)
{
        struct ibmvtpm_crq_queue *crq_q = &ibmvtpm->crq_queue;
        struct ibmvtpm_crq *crq = &crq_q->crq_addr[crq_q->index];

        if (crq->valid & VTPM_MSG_RES) {
                if (++crq_q->index == crq_q->num_entry)
                        crq_q->index = 0;
                smp_rmb();
        } else
                crq = NULL;
        return crq;
}

/**
 * ibmvtpm_crq_process - Process responded crq
 *
 * @crq:        crq to be processed
 * @ibmvtpm:    vtpm device struct
 *
 */
static void ibmvtpm_crq_process(struct ibmvtpm_crq *crq,
                                struct ibmvtpm_dev *ibmvtpm)
{
        int rc = 0;

        switch (crq->valid) {
        case VALID_INIT_CRQ:
                switch (crq->msg) {
                case INIT_CRQ_RES:
                        dev_info(ibmvtpm->dev, "CRQ initialized\n");
                        rc = ibmvtpm_crq_send_init_complete(ibmvtpm);
                        if (rc)
                                dev_err(ibmvtpm->dev, "Unable to send CRQ init complete rc=%d\n", rc);
                        return;
                case INIT_CRQ_COMP_RES:
                        dev_info(ibmvtpm->dev,
                                 "CRQ initialization completed\n");
                        return;
                default:
                        dev_err(ibmvtpm->dev, "Unknown crq message type: %d\n", crq->msg);
                        return;
                }
        case IBMVTPM_VALID_CMD:
                switch (crq->msg) {
                case VTPM_GET_RTCE_BUFFER_SIZE_RES:
                        if (be16_to_cpu(crq->len) <= 0) {
                                dev_err(ibmvtpm->dev, "Invalid rtce size\n");
                                return;
                        }
                        ibmvtpm->rtce_size = be16_to_cpu(crq->len);
                        ibmvtpm->rtce_buf = kmalloc(ibmvtpm->rtce_size,
                                                    GFP_ATOMIC);
                        if (!ibmvtpm->rtce_buf) {
                                dev_err(ibmvtpm->dev, "Failed to allocate memory for rtce buffer\n");
                                return;
                        }

                        ibmvtpm->rtce_dma_handle = dma_map_single(ibmvtpm->dev,
                                ibmvtpm->rtce_buf, ibmvtpm->rtce_size,
                                DMA_BIDIRECTIONAL);

                        if (dma_mapping_error(ibmvtpm->dev,
                                              ibmvtpm->rtce_dma_handle)) {
                                kfree(ibmvtpm->rtce_buf);
                                ibmvtpm->rtce_buf = NULL;
                                dev_err(ibmvtpm->dev, "Failed to dma map rtce buffer\n");
                        }

                        return;
                case VTPM_GET_VERSION_RES:
                        ibmvtpm->vtpm_version = be32_to_cpu(crq->data);
                        return;
                case VTPM_TPM_COMMAND_RES:
                        /* len of the data in rtce buffer */
                        ibmvtpm->res_len = be16_to_cpu(crq->len);
                        ibmvtpm->tpm_processing_cmd = false;
                        wake_up_interruptible(&ibmvtpm->wq);
                        return;
                default:
                        return;
                }
        }
        return;
}

/**
 * ibmvtpm_interrupt -  Interrupt handler
 *
 * @irq:                irq number to handle
 * @vtpm_instance:      vtpm that received interrupt
 *
 * Returns:
 *      IRQ_HANDLED
 **/
static irqreturn_t ibmvtpm_interrupt(int irq, void *vtpm_instance)
{
        struct ibmvtpm_dev *ibmvtpm = (struct ibmvtpm_dev *) vtpm_instance;
        struct ibmvtpm_crq *crq;

        /* while loop is needed for initial setup (get version and
         * get rtce_size). There should be only one tpm request at any
         * given time.
         */
        while ((crq = ibmvtpm_crq_get_next(ibmvtpm)) != NULL) {
                ibmvtpm_crq_process(crq, ibmvtpm);
                crq->valid = 0;
                smp_wmb();
        }

        return IRQ_HANDLED;
}

/**
 * tpm_ibmvtpm_probe - ibm vtpm initialize entry point
 *
 * @vio_dev:    vio device struct
 * @id:         vio device id struct
 *
 * Return:
 *      0 on success.
 *      Non-zero on failure.
 */
static int tpm_ibmvtpm_probe(struct vio_dev *vio_dev,
                                   const struct vio_device_id *id)
{
        struct ibmvtpm_dev *ibmvtpm;
        struct device *dev = &vio_dev->dev;
        struct ibmvtpm_crq_queue *crq_q;
        struct tpm_chip *chip;
        int rc = -ENOMEM, rc1;

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

        ibmvtpm = kzalloc(sizeof(struct ibmvtpm_dev), GFP_KERNEL);
        if (!ibmvtpm) {
                dev_err(dev, "kzalloc for ibmvtpm failed\n");
                goto cleanup;
        }

        ibmvtpm->dev = dev;
        ibmvtpm->vdev = vio_dev;

        crq_q = &ibmvtpm->crq_queue;
        crq_q->crq_addr = (struct ibmvtpm_crq *)get_zeroed_page(GFP_KERNEL);
        if (!crq_q->crq_addr) {
                dev_err(dev, "Unable to allocate memory for crq_addr\n");
                goto cleanup;
        }

        crq_q->num_entry = CRQ_RES_BUF_SIZE / sizeof(*crq_q->crq_addr);
        ibmvtpm->crq_dma_handle = dma_map_single(dev, crq_q->crq_addr,
                                                 CRQ_RES_BUF_SIZE,
                                                 DMA_BIDIRECTIONAL);

        if (dma_mapping_error(dev, ibmvtpm->crq_dma_handle)) {
                dev_err(dev, "dma mapping failed\n");
                goto cleanup;
        }

        rc = plpar_hcall_norets(H_REG_CRQ, vio_dev->unit_address,
                                ibmvtpm->crq_dma_handle, CRQ_RES_BUF_SIZE);
        if (rc == H_RESOURCE)
                rc = ibmvtpm_reset_crq(ibmvtpm);

        if (rc) {
                dev_err(dev, "Unable to register CRQ rc=%d\n", rc);
                goto reg_crq_cleanup;
        }

        rc = request_irq(vio_dev->irq, ibmvtpm_interrupt, 0,
                         tpm_ibmvtpm_driver_name, ibmvtpm);
        if (rc) {
                dev_err(dev, "Error %d register irq 0x%x\n", rc, vio_dev->irq);
                goto init_irq_cleanup;
        }

        rc = vio_enable_interrupts(vio_dev);
        if (rc) {
                dev_err(dev, "Error %d enabling interrupts\n", rc);
                goto init_irq_cleanup;
        }

        init_waitqueue_head(&ibmvtpm->wq);

        crq_q->index = 0;

        dev_set_drvdata(&chip->dev, ibmvtpm);

        spin_lock_init(&ibmvtpm->rtce_lock);

        rc = ibmvtpm_crq_send_init(ibmvtpm);
        if (rc)
                goto init_irq_cleanup;

        rc = ibmvtpm_crq_get_version(ibmvtpm);
        if (rc)
                goto init_irq_cleanup;

        rc = ibmvtpm_crq_get_rtce_size(ibmvtpm);
        if (rc)
                goto init_irq_cleanup;

        return tpm_chip_register(chip);
init_irq_cleanup:
        do {
                rc1 = plpar_hcall_norets(H_FREE_CRQ, vio_dev->unit_address);
        } while (rc1 == H_BUSY || H_IS_LONG_BUSY(rc1));
reg_crq_cleanup:
        dma_unmap_single(dev, ibmvtpm->crq_dma_handle, CRQ_RES_BUF_SIZE,
                         DMA_BIDIRECTIONAL);
cleanup:
        if (ibmvtpm) {
                if (crq_q->crq_addr)
                        free_page((unsigned long)crq_q->crq_addr);
                kfree(ibmvtpm);
        }

        return rc;
}

static struct vio_driver ibmvtpm_driver = {
        .id_table        = tpm_ibmvtpm_device_table,
        .probe           = tpm_ibmvtpm_probe,
        .remove          = tpm_ibmvtpm_remove,
        .get_desired_dma = tpm_ibmvtpm_get_desired_dma,
        .name            = tpm_ibmvtpm_driver_name,
        .pm              = &tpm_ibmvtpm_pm_ops,
};

/**
 * ibmvtpm_module_init - Initialize ibm vtpm module.
 *
 *
 * Return:
 *      0 on success.
 *      Non-zero on failure.
 */
static int __init ibmvtpm_module_init(void)
{
        return vio_register_driver(&ibmvtpm_driver);
}

/**
 * ibmvtpm_module_exit - Tear down ibm vtpm module.
 */
static void __exit ibmvtpm_module_exit(void)
{
        vio_unregister_driver(&ibmvtpm_driver);
}

module_init(ibmvtpm_module_init);
module_exit(ibmvtpm_module_exit);

MODULE_AUTHOR("adlai@us.ibm.com");
MODULE_DESCRIPTION("IBM vTPM Driver");
MODULE_VERSION("1.0");
MODULE_LICENSE("GPL");