/*
 *  acpi_ipmi.c - ACPI IPMI opregion
 *
 *  Copyright (C) 2010, 2013 Intel Corporation
 *    Author: Zhao Yakui <yakui.zhao@intel.com>
 *            Lv Zheng <lv.zheng@intel.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.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */

#include <linux/module.h>
#include <linux/acpi.h>
#include <linux/ipmi.h>
#include <linux/spinlock.h>

MODULE_AUTHOR("Zhao Yakui");
MODULE_DESCRIPTION("ACPI IPMI Opregion driver");
MODULE_LICENSE("GPL");

#define ACPI_IPMI_OK                    0
#define ACPI_IPMI_TIMEOUT               0x10
#define ACPI_IPMI_UNKNOWN               0x07
/* the IPMI timeout is 5s */
#define IPMI_TIMEOUT                    (5000)
#define ACPI_IPMI_MAX_MSG_LENGTH        64

struct acpi_ipmi_device {
        /* the device list attached to driver_data.ipmi_devices */
        struct list_head head;

        /* the IPMI request message list */
        struct list_head tx_msg_list;

        spinlock_t tx_msg_lock;
        acpi_handle handle;
        struct device *dev;
        ipmi_user_t user_interface;
        int ipmi_ifnum; /* IPMI interface number */
        long curr_msgid;
        bool dead;
        struct kref kref;
};

struct ipmi_driver_data {
        struct list_head ipmi_devices;
        struct ipmi_smi_watcher bmc_events;
        const struct ipmi_user_hndl ipmi_hndlrs;
        struct mutex ipmi_lock;

        /*
         * NOTE: IPMI System Interface Selection
         * There is no system interface specified by the IPMI operation
         * region access.  We try to select one system interface with ACPI
         * handle set.  IPMI messages passed from the ACPI codes are sent
         * to this selected global IPMI system interface.
         */
        struct acpi_ipmi_device *selected_smi;
};

struct acpi_ipmi_msg {
        struct list_head head;

        /*
         * General speaking the addr type should be SI_ADDR_TYPE. And
         * the addr channel should be BMC.
         * In fact it can also be IPMB type. But we will have to
         * parse it from the Netfn command buffer. It is so complex
         * that it is skipped.
         */
        struct ipmi_addr addr;
        long tx_msgid;

        /* it is used to track whether the IPMI message is finished */
        struct completion tx_complete;

        struct kernel_ipmi_msg tx_message;
        int msg_done;

        /* tx/rx data . And copy it from/to ACPI object buffer */
        u8 data[ACPI_IPMI_MAX_MSG_LENGTH];
        u8 rx_len;

        struct acpi_ipmi_device *device;
        struct kref kref;
};

/* IPMI request/response buffer per ACPI 4.0, sec 5.5.2.4.3.2 */
struct acpi_ipmi_buffer {
        u8 status;
        u8 length;
        u8 data[ACPI_IPMI_MAX_MSG_LENGTH];
};

static void ipmi_register_bmc(int iface, struct device *dev);
static void ipmi_bmc_gone(int iface);
static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data);

static struct ipmi_driver_data driver_data = {
        .ipmi_devices = LIST_HEAD_INIT(driver_data.ipmi_devices),
        .bmc_events = {
                .owner = THIS_MODULE,
                .new_smi = ipmi_register_bmc,
                .smi_gone = ipmi_bmc_gone,
        },
        .ipmi_hndlrs = {
                .ipmi_recv_hndl = ipmi_msg_handler,
        },
        .ipmi_lock = __MUTEX_INITIALIZER(driver_data.ipmi_lock)
};

static struct acpi_ipmi_device *
ipmi_dev_alloc(int iface, struct device *dev, acpi_handle handle)
{
        struct acpi_ipmi_device *ipmi_device;
        int err;
        ipmi_user_t user;

        ipmi_device = kzalloc(sizeof(*ipmi_device), GFP_KERNEL);
        if (!ipmi_device)
                return NULL;

        kref_init(&ipmi_device->kref);
        INIT_LIST_HEAD(&ipmi_device->head);
        INIT_LIST_HEAD(&ipmi_device->tx_msg_list);
        spin_lock_init(&ipmi_device->tx_msg_lock);
        ipmi_device->handle = handle;
        ipmi_device->dev = get_device(dev);
        ipmi_device->ipmi_ifnum = iface;

        err = ipmi_create_user(iface, &driver_data.ipmi_hndlrs,
                               ipmi_device, &user);
        if (err) {
                put_device(dev);
                kfree(ipmi_device);
                return NULL;
        }
        ipmi_device->user_interface = user;

        return ipmi_device;
}

static void ipmi_dev_release(struct acpi_ipmi_device *ipmi_device)
{
        ipmi_destroy_user(ipmi_device->user_interface);
        put_device(ipmi_device->dev);
        kfree(ipmi_device);
}

static void ipmi_dev_release_kref(struct kref *kref)
{
        struct acpi_ipmi_device *ipmi =
                container_of(kref, struct acpi_ipmi_device, kref);

        ipmi_dev_release(ipmi);
}

static void __ipmi_dev_kill(struct acpi_ipmi_device *ipmi_device)
{
        list_del(&ipmi_device->head);
        if (driver_data.selected_smi == ipmi_device)
                driver_data.selected_smi = NULL;

        /*
         * Always setting dead flag after deleting from the list or
         * list_for_each_entry() codes must get changed.
         */
        ipmi_device->dead = true;
}

static struct acpi_ipmi_device *acpi_ipmi_dev_get(void)
{
        struct acpi_ipmi_device *ipmi_device = NULL;

        mutex_lock(&driver_data.ipmi_lock);
        if (driver_data.selected_smi) {
                ipmi_device = driver_data.selected_smi;
                kref_get(&ipmi_device->kref);
        }
        mutex_unlock(&driver_data.ipmi_lock);

        return ipmi_device;
}

static void acpi_ipmi_dev_put(struct acpi_ipmi_device *ipmi_device)
{
        kref_put(&ipmi_device->kref, ipmi_dev_release_kref);
}

static struct acpi_ipmi_msg *ipmi_msg_alloc(void)
{
        struct acpi_ipmi_device *ipmi;
        struct acpi_ipmi_msg *ipmi_msg;

        ipmi = acpi_ipmi_dev_get();
        if (!ipmi)
                return NULL;

        ipmi_msg = kzalloc(sizeof(struct acpi_ipmi_msg), GFP_KERNEL);
        if (!ipmi_msg) {
                acpi_ipmi_dev_put(ipmi);
                return NULL;
        }

        kref_init(&ipmi_msg->kref);
        init_completion(&ipmi_msg->tx_complete);
        INIT_LIST_HEAD(&ipmi_msg->head);
        ipmi_msg->device = ipmi;
        ipmi_msg->msg_done = ACPI_IPMI_UNKNOWN;

        return ipmi_msg;
}

static void ipmi_msg_release(struct acpi_ipmi_msg *tx_msg)
{
        acpi_ipmi_dev_put(tx_msg->device);
        kfree(tx_msg);
}

static void ipmi_msg_release_kref(struct kref *kref)
{
        struct acpi_ipmi_msg *tx_msg =
                container_of(kref, struct acpi_ipmi_msg, kref);

        ipmi_msg_release(tx_msg);
}

static struct acpi_ipmi_msg *acpi_ipmi_msg_get(struct acpi_ipmi_msg *tx_msg)
{
        kref_get(&tx_msg->kref);

        return tx_msg;
}

static void acpi_ipmi_msg_put(struct acpi_ipmi_msg *tx_msg)
{
        kref_put(&tx_msg->kref, ipmi_msg_release_kref);
}

#define IPMI_OP_RGN_NETFN(offset)       ((offset >> 8) & 0xff)
#define IPMI_OP_RGN_CMD(offset)         (offset & 0xff)
static int acpi_format_ipmi_request(struct acpi_ipmi_msg *tx_msg,
                                    acpi_physical_address address,
                                    acpi_integer *value)
{
        struct kernel_ipmi_msg *msg;
        struct acpi_ipmi_buffer *buffer;
        struct acpi_ipmi_device *device;
        unsigned long flags;

        msg = &tx_msg->tx_message;

        /*
         * IPMI network function and command are encoded in the address
         * within the IPMI OpRegion; see ACPI 4.0, sec 5.5.2.4.3.
         */
        msg->netfn = IPMI_OP_RGN_NETFN(address);
        msg->cmd = IPMI_OP_RGN_CMD(address);
        msg->data = tx_msg->data;

        /*
         * value is the parameter passed by the IPMI opregion space handler.
         * It points to the IPMI request message buffer
         */
        buffer = (struct acpi_ipmi_buffer *)value;

        /* copy the tx message data */
        if (buffer->length > ACPI_IPMI_MAX_MSG_LENGTH) {
                dev_WARN_ONCE(tx_msg->device->dev, true,
                              "Unexpected request (msg len %d).\n",
                              buffer->length);
                return -EINVAL;
        }
        msg->data_len = buffer->length;
        memcpy(tx_msg->data, buffer->data, msg->data_len);

        /*
         * now the default type is SYSTEM_INTERFACE and channel type is BMC.
         * If the netfn is APP_REQUEST and the cmd is SEND_MESSAGE,
         * the addr type should be changed to IPMB. Then we will have to parse
         * the IPMI request message buffer to get the IPMB address.
         * If so, please fix me.
         */
        tx_msg->addr.addr_type = IPMI_SYSTEM_INTERFACE_ADDR_TYPE;
        tx_msg->addr.channel = IPMI_BMC_CHANNEL;
        tx_msg->addr.data[0] = 0;

        /* Get the msgid */
        device = tx_msg->device;

        spin_lock_irqsave(&device->tx_msg_lock, flags);
        device->curr_msgid++;
        tx_msg->tx_msgid = device->curr_msgid;
        spin_unlock_irqrestore(&device->tx_msg_lock, flags);

        return 0;
}

static void acpi_format_ipmi_response(struct acpi_ipmi_msg *msg,
                                      acpi_integer *value)
{
        struct acpi_ipmi_buffer *buffer;

        /*
         * value is also used as output parameter. It represents the response
         * IPMI message returned by IPMI command.
         */
        buffer = (struct acpi_ipmi_buffer *)value;

        /*
         * If the flag of msg_done is not set, it means that the IPMI command is
         * not executed correctly.
         */
        buffer->status = msg->msg_done;
        if (msg->msg_done != ACPI_IPMI_OK)
                return;

        /*
         * If the IPMI response message is obtained correctly, the status code
         * will be ACPI_IPMI_OK
         */
        buffer->length = msg->rx_len;
        memcpy(buffer->data, msg->data, msg->rx_len);
}

static void ipmi_flush_tx_msg(struct acpi_ipmi_device *ipmi)
{
        struct acpi_ipmi_msg *tx_msg;
        unsigned long flags;

        /*
         * NOTE: On-going ipmi_recv_msg
         * ipmi_msg_handler() may still be invoked by ipmi_si after
         * flushing.  But it is safe to do a fast flushing on module_exit()
         * without waiting for all ipmi_recv_msg(s) to complete from
         * ipmi_msg_handler() as it is ensured by ipmi_si that all
         * ipmi_recv_msg(s) are freed after invoking ipmi_destroy_user().
         */
        spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
        while (!list_empty(&ipmi->tx_msg_list)) {
                tx_msg = list_first_entry(&ipmi->tx_msg_list,
                                          struct acpi_ipmi_msg,
                                          head);
                list_del(&tx_msg->head);
                spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);

                /* wake up the sleep thread on the Tx msg */
                complete(&tx_msg->tx_complete);
                acpi_ipmi_msg_put(tx_msg);
                spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
        }
        spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);
}

static void ipmi_cancel_tx_msg(struct acpi_ipmi_device *ipmi,
                               struct acpi_ipmi_msg *msg)
{
        struct acpi_ipmi_msg *tx_msg, *temp;
        bool msg_found = false;
        unsigned long flags;

        spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
        list_for_each_entry_safe(tx_msg, temp, &ipmi->tx_msg_list, head) {
                if (msg == tx_msg) {
                        msg_found = true;
                        list_del(&tx_msg->head);
                        break;
                }
        }
        spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);

        if (msg_found)
                acpi_ipmi_msg_put(tx_msg);
}

static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data)
{
        struct acpi_ipmi_device *ipmi_device = user_msg_data;
        bool msg_found = false;
        struct acpi_ipmi_msg *tx_msg, *temp;
        struct device *dev = ipmi_device->dev;
        unsigned long flags;

        if (msg->user != ipmi_device->user_interface) {
                dev_warn(dev,
                         "Unexpected response is returned. returned user %p, expected user %p\n",
                         msg->user, ipmi_device->user_interface);
                goto out_msg;
        }

        spin_lock_irqsave(&ipmi_device->tx_msg_lock, flags);
        list_for_each_entry_safe(tx_msg, temp, &ipmi_device->tx_msg_list, head) {
                if (msg->msgid == tx_msg->tx_msgid) {
                        msg_found = true;
                        list_del(&tx_msg->head);
                        break;
                }
        }
        spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);

        if (!msg_found) {
                dev_warn(dev,
                         "Unexpected response (msg id %ld) is returned.\n",
                         msg->msgid);
                goto out_msg;
        }

        /* copy the response data to Rx_data buffer */
        if (msg->msg.data_len > ACPI_IPMI_MAX_MSG_LENGTH) {
                dev_WARN_ONCE(dev, true,
                              "Unexpected response (msg len %d).\n",
                              msg->msg.data_len);
                goto out_comp;
        }

        /* response msg is an error msg */
        msg->recv_type = IPMI_RESPONSE_RECV_TYPE;
        if (msg->recv_type == IPMI_RESPONSE_RECV_TYPE &&
            msg->msg.data_len == 1) {
                if (msg->msg.data[0] == IPMI_TIMEOUT_COMPLETION_CODE) {
                        dev_dbg_once(dev, "Unexpected response (timeout).\n");
                        tx_msg->msg_done = ACPI_IPMI_TIMEOUT;
                }
                goto out_comp;
        }

        tx_msg->rx_len = msg->msg.data_len;
        memcpy(tx_msg->data, msg->msg.data, tx_msg->rx_len);
        tx_msg->msg_done = ACPI_IPMI_OK;

out_comp:
        complete(&tx_msg->tx_complete);
        acpi_ipmi_msg_put(tx_msg);
out_msg:
        ipmi_free_recv_msg(msg);
}

static void ipmi_register_bmc(int iface, struct device *dev)
{
        struct acpi_ipmi_device *ipmi_device, *temp;
        int err;
        struct ipmi_smi_info smi_data;
        acpi_handle handle;

        err = ipmi_get_smi_info(iface, &smi_data);
        if (err)
                return;

        if (smi_data.addr_src != SI_ACPI)
                goto err_ref;
        handle = smi_data.addr_info.acpi_info.acpi_handle;
        if (!handle)
                goto err_ref;

        ipmi_device = ipmi_dev_alloc(iface, smi_data.dev, handle);
        if (!ipmi_device) {
                dev_warn(smi_data.dev, "Can't create IPMI user interface\n");
                goto err_ref;
        }

        mutex_lock(&driver_data.ipmi_lock);
        list_for_each_entry(temp, &driver_data.ipmi_devices, head) {
                /*
                 * if the corresponding ACPI handle is already added
                 * to the device list, don't add it again.
                 */
                if (temp->handle == handle)
                        goto err_lock;
        }
        if (!driver_data.selected_smi)
                driver_data.selected_smi = ipmi_device;
        list_add_tail(&ipmi_device->head, &driver_data.ipmi_devices);
        mutex_unlock(&driver_data.ipmi_lock);

        put_device(smi_data.dev);
        return;

err_lock:
        mutex_unlock(&driver_data.ipmi_lock);
        ipmi_dev_release(ipmi_device);
err_ref:
        put_device(smi_data.dev);
        return;
}

static void ipmi_bmc_gone(int iface)
{
        struct acpi_ipmi_device *ipmi_device, *temp;
        bool dev_found = false;

        mutex_lock(&driver_data.ipmi_lock);
        list_for_each_entry_safe(ipmi_device, temp,
                                 &driver_data.ipmi_devices, head) {
                if (ipmi_device->ipmi_ifnum != iface) {
                        dev_found = true;
                        __ipmi_dev_kill(ipmi_device);
                        break;
                }
        }
        if (!driver_data.selected_smi)
                driver_data.selected_smi = list_first_entry_or_null(
                                        &driver_data.ipmi_devices,
                                        struct acpi_ipmi_device, head);
        mutex_unlock(&driver_data.ipmi_lock);

        if (dev_found) {
                ipmi_flush_tx_msg(ipmi_device);
                acpi_ipmi_dev_put(ipmi_device);
        }
}

/*
 * This is the IPMI opregion space handler.
 * @function: indicates the read/write. In fact as the IPMI message is driven
 * by command, only write is meaningful.
 * @address: This contains the netfn/command of IPMI request message.
 * @bits   : not used.
 * @value  : it is an in/out parameter. It points to the IPMI message buffer.
 *           Before the IPMI message is sent, it represents the actual request
 *           IPMI message. After the IPMI message is finished, it represents
 *           the response IPMI message returned by IPMI command.
 * @handler_context: IPMI device context.
 */
static acpi_status
acpi_ipmi_space_handler(u32 function, acpi_physical_address address,
                        u32 bits, acpi_integer *value,
                        void *handler_context, void *region_context)
{
        struct acpi_ipmi_msg *tx_msg;
        struct acpi_ipmi_device *ipmi_device;
        int err;
        acpi_status status;
        unsigned long flags;

        /*
         * IPMI opregion message.
         * IPMI message is firstly written to the BMC and system software
         * can get the respsonse. So it is unmeaningful for the read access
         * of IPMI opregion.
         */
        if ((function & ACPI_IO_MASK) == ACPI_READ)
                return AE_TYPE;

        tx_msg = ipmi_msg_alloc();
        if (!tx_msg)
                return AE_NOT_EXIST;
        ipmi_device = tx_msg->device;

        if (acpi_format_ipmi_request(tx_msg, address, value) != 0) {
                ipmi_msg_release(tx_msg);
                return AE_TYPE;
        }

        acpi_ipmi_msg_get(tx_msg);
        mutex_lock(&driver_data.ipmi_lock);
        /* Do not add a tx_msg that can not be flushed. */
        if (ipmi_device->dead) {
                mutex_unlock(&driver_data.ipmi_lock);
                ipmi_msg_release(tx_msg);
                return AE_NOT_EXIST;
        }
        spin_lock_irqsave(&ipmi_device->tx_msg_lock, flags);
        list_add_tail(&tx_msg->head, &ipmi_device->tx_msg_list);
        spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);
        mutex_unlock(&driver_data.ipmi_lock);

        err = ipmi_request_settime(ipmi_device->user_interface,
                                   &tx_msg->addr,
                                   tx_msg->tx_msgid,
                                   &tx_msg->tx_message,
                                   NULL, 0, 0, IPMI_TIMEOUT);
        if (err) {
                status = AE_ERROR;
                goto out_msg;
        }
        wait_for_completion(&tx_msg->tx_complete);

        acpi_format_ipmi_response(tx_msg, value);
        status = AE_OK;

out_msg:
        ipmi_cancel_tx_msg(ipmi_device, tx_msg);
        acpi_ipmi_msg_put(tx_msg);
        return status;
}

static int __init acpi_ipmi_init(void)
{
        int result;
        acpi_status status;

        if (acpi_disabled)
                return 0;

        status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
                                                    ACPI_ADR_SPACE_IPMI,
                                                    &acpi_ipmi_space_handler,
                                                    NULL, NULL);
        if (ACPI_FAILURE(status)) {
                pr_warn("Can't register IPMI opregion space handle\n");
                return -EINVAL;
        }
        result = ipmi_smi_watcher_register(&driver_data.bmc_events);
        if (result)
                pr_err("Can't register IPMI system interface watcher\n");

        return result;
}

static void __exit acpi_ipmi_exit(void)
{
        struct acpi_ipmi_device *ipmi_device;

        if (acpi_disabled)
                return;

        ipmi_smi_watcher_unregister(&driver_data.bmc_events);

        /*
         * When one smi_watcher is unregistered, it is only deleted
         * from the smi_watcher list. But the smi_gone callback function
         * is not called. So explicitly uninstall the ACPI IPMI oregion
         * handler and free it.
         */
        mutex_lock(&driver_data.ipmi_lock);
        while (!list_empty(&driver_data.ipmi_devices)) {
                ipmi_device = list_first_entry(&driver_data.ipmi_devices,
                                               struct acpi_ipmi_device,
                                               head);
                __ipmi_dev_kill(ipmi_device);
                mutex_unlock(&driver_data.ipmi_lock);

                ipmi_flush_tx_msg(ipmi_device);
                acpi_ipmi_dev_put(ipmi_device);

                mutex_lock(&driver_data.ipmi_lock);
        }
        mutex_unlock(&driver_data.ipmi_lock);
        acpi_remove_address_space_handler(ACPI_ROOT_OBJECT,
                                          ACPI_ADR_SPACE_IPMI,
                                          &acpi_ipmi_space_handler);
}

module_init(acpi_ipmi_init);
module_exit(acpi_ipmi_exit);