/*
 *  ec.c - ACPI Embedded Controller Driver (v3)
 *
 *  Copyright (C) 2001-2015 Intel Corporation
 *    Author: 2014, 2015 Lv Zheng <lv.zheng@intel.com>
 *            2006, 2007 Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>
 *            2006       Denis Sadykov <denis.m.sadykov@intel.com>
 *            2004       Luming Yu <luming.yu@intel.com>
 *            2001, 2002 Andy Grover <andrew.grover@intel.com>
 *            2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
 *  Copyright (C) 2008      Alexey Starikovskiy <astarikovskiy@suse.de>
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  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.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */

/* Uncomment next line to get verbose printout */
/* #define DEBUG */
#define pr_fmt(fmt) "ACPI : EC: " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/acpi.h>
#include <linux/dmi.h>
#include <asm/io.h>

#include "internal.h"

#define ACPI_EC_CLASS                   "embedded_controller"
#define ACPI_EC_DEVICE_NAME             "Embedded Controller"
#define ACPI_EC_FILE_INFO               "info"

/* EC status register */
#define ACPI_EC_FLAG_OBF        0x01    /* Output buffer full */
#define ACPI_EC_FLAG_IBF        0x02    /* Input buffer full */
#define ACPI_EC_FLAG_CMD        0x08    /* Input buffer contains a command */
#define ACPI_EC_FLAG_BURST      0x10    /* burst mode */
#define ACPI_EC_FLAG_SCI        0x20    /* EC-SCI occurred */

/*
 * The SCI_EVT clearing timing is not defined by the ACPI specification.
 * This leads to lots of practical timing issues for the host EC driver.
 * The following variations are defined (from the target EC firmware's
 * perspective):
 * STATUS: After indicating SCI_EVT edge triggered IRQ to the host, the
 *         target can clear SCI_EVT at any time so long as the host can see
 *         the indication by reading the status register (EC_SC). So the
 *         host should re-check SCI_EVT after the first time the SCI_EVT
 *         indication is seen, which is the same time the query request
 *         (QR_EC) is written to the command register (EC_CMD). SCI_EVT set
 *         at any later time could indicate another event. Normally such
 *         kind of EC firmware has implemented an event queue and will
 *         return 0x00 to indicate "no outstanding event".
 * QUERY: After seeing the query request (QR_EC) written to the command
 *        register (EC_CMD) by the host and having prepared the responding
 *        event value in the data register (EC_DATA), the target can safely
 *        clear SCI_EVT because the target can confirm that the current
 *        event is being handled by the host. The host then should check
 *        SCI_EVT right after reading the event response from the data
 *        register (EC_DATA).
 * EVENT: After seeing the event response read from the data register
 *        (EC_DATA) by the host, the target can clear SCI_EVT. As the
 *        target requires time to notice the change in the data register
 *        (EC_DATA), the host may be required to wait additional guarding
 *        time before checking the SCI_EVT again. Such guarding may not be
 *        necessary if the host is notified via another IRQ.
 */
#define ACPI_EC_EVT_TIMING_STATUS       0x00
#define ACPI_EC_EVT_TIMING_QUERY        0x01
#define ACPI_EC_EVT_TIMING_EVENT        0x02

/* EC commands */
enum ec_command {
        ACPI_EC_COMMAND_READ = 0x80,
        ACPI_EC_COMMAND_WRITE = 0x81,
        ACPI_EC_BURST_ENABLE = 0x82,
        ACPI_EC_BURST_DISABLE = 0x83,
        ACPI_EC_COMMAND_QUERY = 0x84,
};

#define ACPI_EC_DELAY           500     /* Wait 500ms max. during EC ops */
#define ACPI_EC_UDELAY_GLK      1000    /* Wait 1ms max. to get global lock */
#define ACPI_EC_UDELAY_POLL     550     /* Wait 1ms for EC transaction polling */
#define ACPI_EC_CLEAR_MAX       100     /* Maximum number of events to query
                                         * when trying to clear the EC */
#define ACPI_EC_MAX_QUERIES     16      /* Maximum number of parallel queries */

enum {
        EC_FLAGS_QUERY_PENDING,         /* Query is pending */
        EC_FLAGS_QUERY_GUARDING,        /* Guard for SCI_EVT check */
        EC_FLAGS_GPE_HANDLER_INSTALLED, /* GPE handler installed */
        EC_FLAGS_EC_HANDLER_INSTALLED,  /* OpReg handler installed */
        EC_FLAGS_STARTED,               /* Driver is started */
        EC_FLAGS_STOPPED,               /* Driver is stopped */
        EC_FLAGS_COMMAND_STORM,         /* GPE storms occurred to the
                                         * current command processing */
};

#define ACPI_EC_COMMAND_POLL            0x01 /* Available for command byte */
#define ACPI_EC_COMMAND_COMPLETE        0x02 /* Completed last byte */

/* ec.c is compiled in acpi namespace so this shows up as acpi.ec_delay param */
static unsigned int ec_delay __read_mostly = ACPI_EC_DELAY;
module_param(ec_delay, uint, 0644);
MODULE_PARM_DESC(ec_delay, "Timeout(ms) waited until an EC command completes");

static unsigned int ec_max_queries __read_mostly = ACPI_EC_MAX_QUERIES;
module_param(ec_max_queries, uint, 0644);
MODULE_PARM_DESC(ec_max_queries, "Maximum parallel _Qxx evaluations");

static bool ec_busy_polling __read_mostly;
module_param(ec_busy_polling, bool, 0644);
MODULE_PARM_DESC(ec_busy_polling, "Use busy polling to advance EC transaction");

static unsigned int ec_polling_guard __read_mostly = ACPI_EC_UDELAY_POLL;
module_param(ec_polling_guard, uint, 0644);
MODULE_PARM_DESC(ec_polling_guard, "Guard time(us) between EC accesses in polling modes");

static unsigned int ec_event_clearing __read_mostly = ACPI_EC_EVT_TIMING_QUERY;

/*
 * If the number of false interrupts per one transaction exceeds
 * this threshold, will think there is a GPE storm happened and
 * will disable the GPE for normal transaction.
 */
static unsigned int ec_storm_threshold  __read_mostly = 8;
module_param(ec_storm_threshold, uint, 0644);
MODULE_PARM_DESC(ec_storm_threshold, "Maxim false GPE numbers not considered as GPE storm");

struct acpi_ec_query_handler {
        struct list_head node;
        acpi_ec_query_func func;
        acpi_handle handle;
        void *data;
        u8 query_bit;
        struct kref kref;
};

struct transaction {
        const u8 *wdata;
        u8 *rdata;
        unsigned short irq_count;
        u8 command;
        u8 wi;
        u8 ri;
        u8 wlen;
        u8 rlen;
        u8 flags;
};

struct acpi_ec_query {
        struct transaction transaction;
        struct work_struct work;
        struct acpi_ec_query_handler *handler;
};

static int acpi_ec_query(struct acpi_ec *ec, u8 *data);
static void advance_transaction(struct acpi_ec *ec);
static void acpi_ec_event_handler(struct work_struct *work);
static void acpi_ec_event_processor(struct work_struct *work);

struct acpi_ec *boot_ec, *first_ec;
EXPORT_SYMBOL(first_ec);
static struct workqueue_struct *ec_query_wq;

static int EC_FLAGS_CLEAR_ON_RESUME; /* Needs acpi_ec_clear() on boot/resume */
static int EC_FLAGS_QUERY_HANDSHAKE; /* Needs QR_EC issued when SCI_EVT set */
static int EC_FLAGS_CORRECT_ECDT; /* Needs ECDT port address correction */

/* --------------------------------------------------------------------------
 *                           Logging/Debugging
 * -------------------------------------------------------------------------- */

/*
 * Splitters used by the developers to track the boundary of the EC
 * handling processes.
 */
#ifdef DEBUG
#define EC_DBG_SEP      " "
#define EC_DBG_DRV      "+++++"
#define EC_DBG_STM      "====="
#define EC_DBG_REQ      "*****"
#define EC_DBG_EVT      "#####"
#else
#define EC_DBG_SEP      ""
#define EC_DBG_DRV
#define EC_DBG_STM
#define EC_DBG_REQ
#define EC_DBG_EVT
#endif

#define ec_log_raw(fmt, ...) \
        pr_info(fmt "\n", ##__VA_ARGS__)
#define ec_dbg_raw(fmt, ...) \
        pr_debug(fmt "\n", ##__VA_ARGS__)
#define ec_log(filter, fmt, ...) \
        ec_log_raw(filter EC_DBG_SEP fmt EC_DBG_SEP filter, ##__VA_ARGS__)
#define ec_dbg(filter, fmt, ...) \
        ec_dbg_raw(filter EC_DBG_SEP fmt EC_DBG_SEP filter, ##__VA_ARGS__)

#define ec_log_drv(fmt, ...) \
        ec_log(EC_DBG_DRV, fmt, ##__VA_ARGS__)
#define ec_dbg_drv(fmt, ...) \
        ec_dbg(EC_DBG_DRV, fmt, ##__VA_ARGS__)
#define ec_dbg_stm(fmt, ...) \
        ec_dbg(EC_DBG_STM, fmt, ##__VA_ARGS__)
#define ec_dbg_req(fmt, ...) \
        ec_dbg(EC_DBG_REQ, fmt, ##__VA_ARGS__)
#define ec_dbg_evt(fmt, ...) \
        ec_dbg(EC_DBG_EVT, fmt, ##__VA_ARGS__)
#define ec_dbg_ref(ec, fmt, ...) \
        ec_dbg_raw("%lu: " fmt, ec->reference_count, ## __VA_ARGS__)

/* --------------------------------------------------------------------------
 *                           Device Flags
 * -------------------------------------------------------------------------- */

static bool acpi_ec_started(struct acpi_ec *ec)
{
        return test_bit(EC_FLAGS_STARTED, &ec->flags) &&
               !test_bit(EC_FLAGS_STOPPED, &ec->flags);
}

static bool acpi_ec_flushed(struct acpi_ec *ec)
{
        return ec->reference_count == 1;
}

/* --------------------------------------------------------------------------
 *                           EC Registers
 * -------------------------------------------------------------------------- */

static inline u8 acpi_ec_read_status(struct acpi_ec *ec)
{
        u8 x = inb(ec->command_addr);

        ec_dbg_raw("EC_SC(R) = 0x%2.2x "
                   "SCI_EVT=%d BURST=%d CMD=%d IBF=%d OBF=%d",
                   x,
                   !!(x & ACPI_EC_FLAG_SCI),
                   !!(x & ACPI_EC_FLAG_BURST),
                   !!(x & ACPI_EC_FLAG_CMD),
                   !!(x & ACPI_EC_FLAG_IBF),
                   !!(x & ACPI_EC_FLAG_OBF));
        return x;
}

static inline u8 acpi_ec_read_data(struct acpi_ec *ec)
{
        u8 x = inb(ec->data_addr);

        ec->timestamp = jiffies;
        ec_dbg_raw("EC_DATA(R) = 0x%2.2x", x);
        return x;
}

static inline void acpi_ec_write_cmd(struct acpi_ec *ec, u8 command)
{
        ec_dbg_raw("EC_SC(W) = 0x%2.2x", command);
        outb(command, ec->command_addr);
        ec->timestamp = jiffies;
}

static inline void acpi_ec_write_data(struct acpi_ec *ec, u8 data)
{
        ec_dbg_raw("EC_DATA(W) = 0x%2.2x", data);
        outb(data, ec->data_addr);
        ec->timestamp = jiffies;
}

#ifdef DEBUG
static const char *acpi_ec_cmd_string(u8 cmd)
{
        switch (cmd) {
        case 0x80:
                return "RD_EC";
        case 0x81:
                return "WR_EC";
        case 0x82:
                return "BE_EC";
        case 0x83:
                return "BD_EC";
        case 0x84:
                return "QR_EC";
        }
        return "UNKNOWN";
}
#else
#define acpi_ec_cmd_string(cmd)         "UNDEF"
#endif

/* --------------------------------------------------------------------------
 *                           GPE Registers
 * -------------------------------------------------------------------------- */

static inline bool acpi_ec_is_gpe_raised(struct acpi_ec *ec)
{
        acpi_event_status gpe_status = 0;

        (void)acpi_get_gpe_status(NULL, ec->gpe, &gpe_status);
        return (gpe_status & ACPI_EVENT_FLAG_STATUS_SET) ? true : false;
}

static inline void acpi_ec_enable_gpe(struct acpi_ec *ec, bool open)
{
        if (open)
                acpi_enable_gpe(NULL, ec->gpe);
        else {
                BUG_ON(ec->reference_count < 1);
                acpi_set_gpe(NULL, ec->gpe, ACPI_GPE_ENABLE);
        }
        if (acpi_ec_is_gpe_raised(ec)) {
                /*
                 * On some platforms, EN=1 writes cannot trigger GPE. So
                 * software need to manually trigger a pseudo GPE event on
                 * EN=1 writes.
                 */
                ec_dbg_raw("Polling quirk");
                advance_transaction(ec);
        }
}

static inline void acpi_ec_disable_gpe(struct acpi_ec *ec, bool close)
{
        if (close)
                acpi_disable_gpe(NULL, ec->gpe);
        else {
                BUG_ON(ec->reference_count < 1);
                acpi_set_gpe(NULL, ec->gpe, ACPI_GPE_DISABLE);
        }
}

static inline void acpi_ec_clear_gpe(struct acpi_ec *ec)
{
        /*
         * GPE STS is a W1C register, which means:
         * 1. Software can clear it without worrying about clearing other
         *    GPEs' STS bits when the hardware sets them in parallel.
         * 2. As long as software can ensure only clearing it when it is
         *    set, hardware won't set it in parallel.
         * So software can clear GPE in any contexts.
         * Warning: do not move the check into advance_transaction() as the
         * EC commands will be sent without GPE raised.
         */
        if (!acpi_ec_is_gpe_raised(ec))
                return;
        acpi_clear_gpe(NULL, ec->gpe);
}

/* --------------------------------------------------------------------------
 *                           Transaction Management
 * -------------------------------------------------------------------------- */

static void acpi_ec_submit_request(struct acpi_ec *ec)
{
        ec->reference_count++;
        if (test_bit(EC_FLAGS_GPE_HANDLER_INSTALLED, &ec->flags) &&
            ec->reference_count == 1)
                acpi_ec_enable_gpe(ec, true);
}

static void acpi_ec_complete_request(struct acpi_ec *ec)
{
        bool flushed = false;

        ec->reference_count--;
        if (test_bit(EC_FLAGS_GPE_HANDLER_INSTALLED, &ec->flags) &&
            ec->reference_count == 0)
                acpi_ec_disable_gpe(ec, true);
        flushed = acpi_ec_flushed(ec);
        if (flushed)
                wake_up(&ec->wait);
}

static void acpi_ec_set_storm(struct acpi_ec *ec, u8 flag)
{
        if (!test_bit(flag, &ec->flags)) {
                acpi_ec_disable_gpe(ec, false);
                ec_dbg_drv("Polling enabled");
                set_bit(flag, &ec->flags);
        }
}

static void acpi_ec_clear_storm(struct acpi_ec *ec, u8 flag)
{
        if (test_bit(flag, &ec->flags)) {
                clear_bit(flag, &ec->flags);
                acpi_ec_enable_gpe(ec, false);
                ec_dbg_drv("Polling disabled");
        }
}

/*
 * acpi_ec_submit_flushable_request() - Increase the reference count unless
 *                                      the flush operation is not in
 *                                      progress
 * @ec: the EC device
 *
 * This function must be used before taking a new action that should hold
 * the reference count.  If this function returns false, then the action
 * must be discarded or it will prevent the flush operation from being
 * completed.
 */
static bool acpi_ec_submit_flushable_request(struct acpi_ec *ec)
{
        if (!acpi_ec_started(ec))
                return false;
        acpi_ec_submit_request(ec);
        return true;
}

static void acpi_ec_submit_query(struct acpi_ec *ec)
{
        if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags)) {
                ec_dbg_evt("Command(%s) submitted/blocked",
                           acpi_ec_cmd_string(ACPI_EC_COMMAND_QUERY));
                ec->nr_pending_queries++;
                schedule_work(&ec->work);
        }
}

static void acpi_ec_complete_query(struct acpi_ec *ec)
{
        if (test_bit(EC_FLAGS_QUERY_PENDING, &ec->flags)) {
                clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
                ec_dbg_evt("Command(%s) unblocked",
                           acpi_ec_cmd_string(ACPI_EC_COMMAND_QUERY));
        }
}

static bool acpi_ec_guard_event(struct acpi_ec *ec)
{
        bool guarded = true;
        unsigned long flags;

        spin_lock_irqsave(&ec->lock, flags);
        /*
         * If firmware SCI_EVT clearing timing is "event", we actually
         * don't know when the SCI_EVT will be cleared by firmware after
         * evaluating _Qxx, so we need to re-check SCI_EVT after waiting an
         * acceptable period.
         *
         * The guarding period begins when EC_FLAGS_QUERY_PENDING is
         * flagged, which means SCI_EVT check has just been performed.
         * But if the current transaction is ACPI_EC_COMMAND_QUERY, the
         * guarding should have already been performed (via
         * EC_FLAGS_QUERY_GUARDING) and should not be applied so that the
         * ACPI_EC_COMMAND_QUERY transaction can be transitioned into
         * ACPI_EC_COMMAND_POLL state immediately.
         */
        if (ec_event_clearing == ACPI_EC_EVT_TIMING_STATUS ||
            ec_event_clearing == ACPI_EC_EVT_TIMING_QUERY ||
            !test_bit(EC_FLAGS_QUERY_PENDING, &ec->flags) ||
            (ec->curr && ec->curr->command == ACPI_EC_COMMAND_QUERY))
                guarded = false;
        spin_unlock_irqrestore(&ec->lock, flags);
        return guarded;
}

static int ec_transaction_polled(struct acpi_ec *ec)
{
        unsigned long flags;
        int ret = 0;

        spin_lock_irqsave(&ec->lock, flags);
        if (ec->curr && (ec->curr->flags & ACPI_EC_COMMAND_POLL))
                ret = 1;
        spin_unlock_irqrestore(&ec->lock, flags);
        return ret;
}

static int ec_transaction_completed(struct acpi_ec *ec)
{
        unsigned long flags;
        int ret = 0;

        spin_lock_irqsave(&ec->lock, flags);
        if (ec->curr && (ec->curr->flags & ACPI_EC_COMMAND_COMPLETE))
                ret = 1;
        spin_unlock_irqrestore(&ec->lock, flags);
        return ret;
}

static inline void ec_transaction_transition(struct acpi_ec *ec, unsigned long flag)
{
        ec->curr->flags |= flag;
        if (ec->curr->command == ACPI_EC_COMMAND_QUERY) {
                if (ec_event_clearing == ACPI_EC_EVT_TIMING_STATUS &&
                    flag == ACPI_EC_COMMAND_POLL)
                        acpi_ec_complete_query(ec);
                if (ec_event_clearing == ACPI_EC_EVT_TIMING_QUERY &&
                    flag == ACPI_EC_COMMAND_COMPLETE)
                        acpi_ec_complete_query(ec);
                if (ec_event_clearing == ACPI_EC_EVT_TIMING_EVENT &&
                    flag == ACPI_EC_COMMAND_COMPLETE)
                        set_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags);
        }
}

static void advance_transaction(struct acpi_ec *ec)
{
        struct transaction *t;
        u8 status;
        bool wakeup = false;

        ec_dbg_stm("%s (%d)", in_interrupt() ? "IRQ" : "TASK",
                   smp_processor_id());
        /*
         * By always clearing STS before handling all indications, we can
         * ensure a hardware STS 0->1 change after this clearing can always
         * trigger a GPE interrupt.
         */
        acpi_ec_clear_gpe(ec);
        status = acpi_ec_read_status(ec);
        t = ec->curr;
        /*
         * Another IRQ or a guarded polling mode advancement is detected,
         * the next QR_EC submission is then allowed.
         */
        if (!t || !(t->flags & ACPI_EC_COMMAND_POLL)) {
                if (ec_event_clearing == ACPI_EC_EVT_TIMING_EVENT &&
                    (!ec->nr_pending_queries ||
                     test_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags))) {
                        clear_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags);
                        acpi_ec_complete_query(ec);
                }
        }
        if (!t)
                goto err;
        if (t->flags & ACPI_EC_COMMAND_POLL) {
                if (t->wlen > t->wi) {
                        if ((status & ACPI_EC_FLAG_IBF) == 0)
                                acpi_ec_write_data(ec, t->wdata[t->wi++]);
                        else
                                goto err;
                } else if (t->rlen > t->ri) {
                        if ((status & ACPI_EC_FLAG_OBF) == 1) {
                                t->rdata[t->ri++] = acpi_ec_read_data(ec);
                                if (t->rlen == t->ri) {
                                        ec_transaction_transition(ec, ACPI_EC_COMMAND_COMPLETE);
                                        if (t->command == ACPI_EC_COMMAND_QUERY)
                                                ec_dbg_evt("Command(%s) completed by hardware",
                                                           acpi_ec_cmd_string(ACPI_EC_COMMAND_QUERY));
                                        wakeup = true;
                                }
                        } else
                                goto err;
                } else if (t->wlen == t->wi &&
                           (status & ACPI_EC_FLAG_IBF) == 0) {
                        ec_transaction_transition(ec, ACPI_EC_COMMAND_COMPLETE);
                        wakeup = true;
                }
                goto out;
        } else {
                if (EC_FLAGS_QUERY_HANDSHAKE &&
                    !(status & ACPI_EC_FLAG_SCI) &&
                    (t->command == ACPI_EC_COMMAND_QUERY)) {
                        ec_transaction_transition(ec, ACPI_EC_COMMAND_POLL);
                        t->rdata[t->ri++] = 0x00;
                        ec_transaction_transition(ec, ACPI_EC_COMMAND_COMPLETE);
                        ec_dbg_evt("Command(%s) completed by software",
                                   acpi_ec_cmd_string(ACPI_EC_COMMAND_QUERY));
                        wakeup = true;
                } else if ((status & ACPI_EC_FLAG_IBF) == 0) {
                        acpi_ec_write_cmd(ec, t->command);
                        ec_transaction_transition(ec, ACPI_EC_COMMAND_POLL);
                } else
                        goto err;
                goto out;
        }
err:
        /*
         * If SCI bit is set, then don't think it's a false IRQ
         * otherwise will take a not handled IRQ as a false one.
         */
        if (!(status & ACPI_EC_FLAG_SCI)) {
                if (in_interrupt() && t) {
                        if (t->irq_count < ec_storm_threshold)
                                ++t->irq_count;
                        /* Allow triggering on 0 threshold */
                        if (t->irq_count == ec_storm_threshold)
                                acpi_ec_set_storm(ec, EC_FLAGS_COMMAND_STORM);
                }
        }
out:
        if (status & ACPI_EC_FLAG_SCI)
                acpi_ec_submit_query(ec);
        if (wakeup && in_interrupt())
                wake_up(&ec->wait);
}

static void start_transaction(struct acpi_ec *ec)
{
        ec->curr->irq_count = ec->curr->wi = ec->curr->ri = 0;
        ec->curr->flags = 0;
}

static int ec_guard(struct acpi_ec *ec)
{
        unsigned long guard = usecs_to_jiffies(ec_polling_guard);
        unsigned long timeout = ec->timestamp + guard;

        /* Ensure guarding period before polling EC status */
        do {
                if (ec_busy_polling) {
                        /* Perform busy polling */
                        if (ec_transaction_completed(ec))
                                return 0;
                        udelay(jiffies_to_usecs(guard));
                } else {
                        /*
                         * Perform wait polling
                         * 1. Wait the transaction to be completed by the
                         *    GPE handler after the transaction enters
                         *    ACPI_EC_COMMAND_POLL state.
                         * 2. A special guarding logic is also required
                         *    for event clearing mode "event" before the
                         *    transaction enters ACPI_EC_COMMAND_POLL
                         *    state.
                         */
                        if (!ec_transaction_polled(ec) &&
                            !acpi_ec_guard_event(ec))
                                break;
                        if (wait_event_timeout(ec->wait,
                                               ec_transaction_completed(ec),
                                               guard))
                                return 0;
                }
        } while (time_before(jiffies, timeout));
        return -ETIME;
}

static int ec_poll(struct acpi_ec *ec)
{
        unsigned long flags;
        int repeat = 5; /* number of command restarts */

        while (repeat--) {
                unsigned long delay = jiffies +
                        msecs_to_jiffies(ec_delay);
                do {
                        if (!ec_guard(ec))
                                return 0;
                        spin_lock_irqsave(&ec->lock, flags);
                        advance_transaction(ec);
                        spin_unlock_irqrestore(&ec->lock, flags);
                } while (time_before(jiffies, delay));
                pr_debug("controller reset, restart transaction\n");
                spin_lock_irqsave(&ec->lock, flags);
                start_transaction(ec);
                spin_unlock_irqrestore(&ec->lock, flags);
        }
        return -ETIME;
}

static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
                                        struct transaction *t)
{
        unsigned long tmp;
        int ret = 0;

        /* start transaction */
        spin_lock_irqsave(&ec->lock, tmp);
        /* Enable GPE for command processing (IBF=0/OBF=1) */
        if (!acpi_ec_submit_flushable_request(ec)) {
                ret = -EINVAL;
                goto unlock;
        }
        ec_dbg_ref(ec, "Increase command");
        /* following two actions should be kept atomic */
        ec->curr = t;
        ec_dbg_req("Command(%s) started", acpi_ec_cmd_string(t->command));
        start_transaction(ec);
        spin_unlock_irqrestore(&ec->lock, tmp);

        ret = ec_poll(ec);

        spin_lock_irqsave(&ec->lock, tmp);
        if (t->irq_count == ec_storm_threshold)
                acpi_ec_clear_storm(ec, EC_FLAGS_COMMAND_STORM);
        ec_dbg_req("Command(%s) stopped", acpi_ec_cmd_string(t->command));
        ec->curr = NULL;
        /* Disable GPE for command processing (IBF=0/OBF=1) */
        acpi_ec_complete_request(ec);
        ec_dbg_ref(ec, "Decrease command");
unlock:
        spin_unlock_irqrestore(&ec->lock, tmp);
        return ret;
}

static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
{
        int status;
        u32 glk;

        if (!ec || (!t) || (t->wlen && !t->wdata) || (t->rlen && !t->rdata))
                return -EINVAL;
        if (t->rdata)
                memset(t->rdata, 0, t->rlen);

        mutex_lock(&ec->mutex);
        if (ec->global_lock) {
                status = acpi_acquire_global_lock(ACPI_EC_UDELAY_GLK, &glk);
                if (ACPI_FAILURE(status)) {
                        status = -ENODEV;
                        goto unlock;
                }
        }

        status = acpi_ec_transaction_unlocked(ec, t);

        if (ec->global_lock)
                acpi_release_global_lock(glk);
unlock:
        mutex_unlock(&ec->mutex);
        return status;
}

static int acpi_ec_burst_enable(struct acpi_ec *ec)
{
        u8 d;
        struct transaction t = {.command = ACPI_EC_BURST_ENABLE,
                                .wdata = NULL, .rdata = &d,
                                .wlen = 0, .rlen = 1};

        return acpi_ec_transaction(ec, &t);
}

static int acpi_ec_burst_disable(struct acpi_ec *ec)
{
        struct transaction t = {.command = ACPI_EC_BURST_DISABLE,
                                .wdata = NULL, .rdata = NULL,
                                .wlen = 0, .rlen = 0};

        return (acpi_ec_read_status(ec) & ACPI_EC_FLAG_BURST) ?
                                acpi_ec_transaction(ec, &t) : 0;
}

static int acpi_ec_read(struct acpi_ec *ec, u8 address, u8 *data)
{
        int result;
        u8 d;
        struct transaction t = {.command = ACPI_EC_COMMAND_READ,
                                .wdata = &address, .rdata = &d,
                                .wlen = 1, .rlen = 1};

        result = acpi_ec_transaction(ec, &t);
        *data = d;
        return result;
}

static int acpi_ec_write(struct acpi_ec *ec, u8 address, u8 data)
{
        u8 wdata[2] = { address, data };
        struct transaction t = {.command = ACPI_EC_COMMAND_WRITE,
                                .wdata = wdata, .rdata = NULL,
                                .wlen = 2, .rlen = 0};

        return acpi_ec_transaction(ec, &t);
}

int ec_read(u8 addr, u8 *val)
{
        int err;
        u8 temp_data;

        if (!first_ec)
                return -ENODEV;

        err = acpi_ec_read(first_ec, addr, &temp_data);

        if (!err) {
                *val = temp_data;
                return 0;
        }
        return err;
}
EXPORT_SYMBOL(ec_read);

int ec_write(u8 addr, u8 val)
{
        int err;

        if (!first_ec)
                return -ENODEV;

        err = acpi_ec_write(first_ec, addr, val);

        return err;
}
EXPORT_SYMBOL(ec_write);

int ec_transaction(u8 command,
                   const u8 *wdata, unsigned wdata_len,
                   u8 *rdata, unsigned rdata_len)
{
        struct transaction t = {.command = command,
                                .wdata = wdata, .rdata = rdata,
                                .wlen = wdata_len, .rlen = rdata_len};

        if (!first_ec)
                return -ENODEV;

        return acpi_ec_transaction(first_ec, &t);
}
EXPORT_SYMBOL(ec_transaction);

/* Get the handle to the EC device */
acpi_handle ec_get_handle(void)
{
        if (!first_ec)
                return NULL;
        return first_ec->handle;
}
EXPORT_SYMBOL(ec_get_handle);

/*
 * Process _Q events that might have accumulated in the EC.
 * Run with locked ec mutex.
 */
static void acpi_ec_clear(struct acpi_ec *ec)
{
        int i, status;
        u8 value = 0;

        for (i = 0; i < ACPI_EC_CLEAR_MAX; i++) {
                status = acpi_ec_query(ec, &value);
                if (status || !value)
                        break;
        }

        if (unlikely(i == ACPI_EC_CLEAR_MAX))
                pr_warn("Warning: Maximum of %d stale EC events cleared\n", i);
        else
                pr_info("%d stale EC events cleared\n", i);
}

static void acpi_ec_start(struct acpi_ec *ec, bool resuming)
{
        unsigned long flags;

        spin_lock_irqsave(&ec->lock, flags);
        if (!test_and_set_bit(EC_FLAGS_STARTED, &ec->flags)) {
                ec_dbg_drv("Starting EC");
                /* Enable GPE for event processing (SCI_EVT=1) */
                if (!resuming) {
                        acpi_ec_submit_request(ec);
                        ec_dbg_ref(ec, "Increase driver");
                }
                ec_log_drv("EC started");
        }
        spin_unlock_irqrestore(&ec->lock, flags);
}

static bool acpi_ec_stopped(struct acpi_ec *ec)
{
        unsigned long flags;
        bool flushed;

        spin_lock_irqsave(&ec->lock, flags);
        flushed = acpi_ec_flushed(ec);
        spin_unlock_irqrestore(&ec->lock, flags);
        return flushed;
}

static void acpi_ec_stop(struct acpi_ec *ec, bool suspending)
{
        unsigned long flags;

        spin_lock_irqsave(&ec->lock, flags);
        if (acpi_ec_started(ec)) {
                ec_dbg_drv("Stopping EC");
                set_bit(EC_FLAGS_STOPPED, &ec->flags);
                spin_unlock_irqrestore(&ec->lock, flags);
                wait_event(ec->wait, acpi_ec_stopped(ec));
                spin_lock_irqsave(&ec->lock, flags);
                /* Disable GPE for event processing (SCI_EVT=1) */
                if (!suspending) {
                        acpi_ec_complete_request(ec);
                        ec_dbg_ref(ec, "Decrease driver");
                }
                clear_bit(EC_FLAGS_STARTED, &ec->flags);
                clear_bit(EC_FLAGS_STOPPED, &ec->flags);
                ec_log_drv("EC stopped");
        }
        spin_unlock_irqrestore(&ec->lock, flags);
}

void acpi_ec_block_transactions(void)
{
        struct acpi_ec *ec = first_ec;

        if (!ec)
                return;

        mutex_lock(&ec->mutex);
        /* Prevent transactions from being carried out */
        acpi_ec_stop(ec, true);
        mutex_unlock(&ec->mutex);
}

void acpi_ec_unblock_transactions(void)
{
        struct acpi_ec *ec = first_ec;

        if (!ec)
                return;

        /* Allow transactions to be carried out again */
        acpi_ec_start(ec, true);

        if (EC_FLAGS_CLEAR_ON_RESUME)
                acpi_ec_clear(ec);
}

void acpi_ec_unblock_transactions_early(void)
{
        /*
         * Allow transactions to happen again (this function is called from
         * atomic context during wakeup, so we don't need to acquire the mutex).
         */
        if (first_ec)
                acpi_ec_start(first_ec, true);
}

/* --------------------------------------------------------------------------
                                Event Management
   -------------------------------------------------------------------------- */
static struct acpi_ec_query_handler *
acpi_ec_get_query_handler(struct acpi_ec_query_handler *handler)
{
        if (handler)
                kref_get(&handler->kref);
        return handler;
}

static struct acpi_ec_query_handler *
acpi_ec_get_query_handler_by_value(struct acpi_ec *ec, u8 value)
{
        struct acpi_ec_query_handler *handler;
        bool found = false;

        mutex_lock(&ec->mutex);
        list_for_each_entry(handler, &ec->list, node) {
                if (value == handler->query_bit) {
                        found = true;
                        break;
                }
        }
        mutex_unlock(&ec->mutex);
        return found ? acpi_ec_get_query_handler(handler) : NULL;
}

static void acpi_ec_query_handler_release(struct kref *kref)
{
        struct acpi_ec_query_handler *handler =
                container_of(kref, struct acpi_ec_query_handler, kref);

        kfree(handler);
}

static void acpi_ec_put_query_handler(struct acpi_ec_query_handler *handler)
{
        kref_put(&handler->kref, acpi_ec_query_handler_release);
}

int acpi_ec_add_query_handler(struct acpi_ec *ec, u8 query_bit,
                              acpi_handle handle, acpi_ec_query_func func,
                              void *data)
{
        struct acpi_ec_query_handler *handler =
            kzalloc(sizeof(struct acpi_ec_query_handler), GFP_KERNEL);

        if (!handler)
                return -ENOMEM;

        handler->query_bit = query_bit;
        handler->handle = handle;
        handler->func = func;
        handler->data = data;
        mutex_lock(&ec->mutex);
        kref_init(&handler->kref);

        list_add(&handler->node, &ec->list);
        mutex_unlock(&ec->mutex);
        return 0;
}
EXPORT_SYMBOL_GPL(acpi_ec_add_query_handler);

static void acpi_ec_remove_query_handlers(struct acpi_ec *ec,
                                          bool remove_all, u8 query_bit)
{
        struct acpi_ec_query_handler *handler, *tmp;
        LIST_HEAD(free_list);

        mutex_lock(&ec->mutex);
        list_for_each_entry_safe(handler, tmp, &ec->list, node) {
                if (remove_all || query_bit == handler->query_bit) {
                        list_del_init(&handler->node);
                        list_add(&handler->node, &free_list);
                }
        }
        mutex_unlock(&ec->mutex);
        list_for_each_entry_safe(handler, tmp, &free_list, node)
                acpi_ec_put_query_handler(handler);
}

void acpi_ec_remove_query_handler(struct acpi_ec *ec, u8 query_bit)
{
        acpi_ec_remove_query_handlers(ec, false, query_bit);
}
EXPORT_SYMBOL_GPL(acpi_ec_remove_query_handler);

static struct acpi_ec_query *acpi_ec_create_query(u8 *pval)
{
        struct acpi_ec_query *q;
        struct transaction *t;

        q = kzalloc(sizeof (struct acpi_ec_query), GFP_KERNEL);
        if (!q)
                return NULL;
        INIT_WORK(&q->work, acpi_ec_event_processor);
        t = &q->transaction;
        t->command = ACPI_EC_COMMAND_QUERY;
        t->rdata = pval;
        t->rlen = 1;
        return q;
}

static void acpi_ec_delete_query(struct acpi_ec_query *q)
{
        if (q) {
                if (q->handler)
                        acpi_ec_put_query_handler(q->handler);
                kfree(q);
        }
}

static void acpi_ec_event_processor(struct work_struct *work)
{
        struct acpi_ec_query *q = container_of(work, struct acpi_ec_query, work);
        struct acpi_ec_query_handler *handler = q->handler;

        ec_dbg_evt("Query(0x%02x) started", handler->query_bit);
        if (handler->func)
                handler->func(handler->data);
        else if (handler->handle)
                acpi_evaluate_object(handler->handle, NULL, NULL, NULL);
        ec_dbg_evt("Query(0x%02x) stopped", handler->query_bit);
        acpi_ec_delete_query(q);
}

static int acpi_ec_query(struct acpi_ec *ec, u8 *data)
{
        u8 value = 0;
        int result;
        struct acpi_ec_query *q;

        q = acpi_ec_create_query(&value);
        if (!q)
                return -ENOMEM;

        /*
         * Query the EC to find out which _Qxx method we need to evaluate.
         * Note that successful completion of the query causes the ACPI_EC_SCI
         * bit to be cleared (and thus clearing the interrupt source).
         */
        result = acpi_ec_transaction(ec, &q->transaction);
        if (!value)
                result = -ENODATA;
        if (result)
                goto err_exit;

        q->handler = acpi_ec_get_query_handler_by_value(ec, value);
        if (!q->handler) {
                result = -ENODATA;
                goto err_exit;
        }

        /*
         * It is reported that _Qxx are evaluated in a parallel way on
         * Windows:
         * https://bugzilla.kernel.org/show_bug.cgi?id=94411
         *
         * Put this log entry before schedule_work() in order to make
         * it appearing before any other log entries occurred during the
         * work queue execution.
         */
        ec_dbg_evt("Query(0x%02x) scheduled", value);
        if (!queue_work(ec_query_wq, &q->work)) {
                ec_dbg_evt("Query(0x%02x) overlapped", value);
                result = -EBUSY;
        }

err_exit:
        if (result)
                acpi_ec_delete_query(q);
        if (data)
                *data = value;
        return result;
}

static void acpi_ec_check_event(struct acpi_ec *ec)
{
        unsigned long flags;

        if (ec_event_clearing == ACPI_EC_EVT_TIMING_EVENT) {
                if (ec_guard(ec)) {
                        spin_lock_irqsave(&ec->lock, flags);
                        /*
                         * Take care of the SCI_EVT unless no one else is
                         * taking care of it.
                         */
                        if (!ec->curr)
                                advance_transaction(ec);
                        spin_unlock_irqrestore(&ec->lock, flags);
                }
        }
}

static void acpi_ec_event_handler(struct work_struct *work)
{
        unsigned long flags;
        struct acpi_ec *ec = container_of(work, struct acpi_ec, work);

        ec_dbg_evt("Event started");

        spin_lock_irqsave(&ec->lock, flags);
        while (ec->nr_pending_queries) {
                spin_unlock_irqrestore(&ec->lock, flags);
                (void)acpi_ec_query(ec, NULL);
                spin_lock_irqsave(&ec->lock, flags);
                ec->nr_pending_queries--;
                /*
                 * Before exit, make sure that this work item can be
                 * scheduled again. There might be QR_EC failures, leaving
                 * EC_FLAGS_QUERY_PENDING uncleared and preventing this work
                 * item from being scheduled again.
                 */
                if (!ec->nr_pending_queries) {
                        if (ec_event_clearing == ACPI_EC_EVT_TIMING_STATUS ||
                            ec_event_clearing == ACPI_EC_EVT_TIMING_QUERY)
                                acpi_ec_complete_query(ec);
                }
        }
        spin_unlock_irqrestore(&ec->lock, flags);

        ec_dbg_evt("Event stopped");

        acpi_ec_check_event(ec);
}

static u32 acpi_ec_gpe_handler(acpi_handle gpe_device,
        u32 gpe_number, void *data)
{
        unsigned long flags;
        struct acpi_ec *ec = data;

        spin_lock_irqsave(&ec->lock, flags);
        advance_transaction(ec);
        spin_unlock_irqrestore(&ec->lock, flags);
        return ACPI_INTERRUPT_HANDLED;
}

/* --------------------------------------------------------------------------
 *                           Address Space Management
 * -------------------------------------------------------------------------- */

static acpi_status
acpi_ec_space_handler(u32 function, acpi_physical_address address,
                      u32 bits, u64 *value64,
                      void *handler_context, void *region_context)
{
        struct acpi_ec *ec = handler_context;
        int result = 0, i, bytes = bits / 8;
        u8 *value = (u8 *)value64;

        if ((address > 0xFF) || !value || !handler_context)
                return AE_BAD_PARAMETER;

        if (function != ACPI_READ && function != ACPI_WRITE)
                return AE_BAD_PARAMETER;

        if (ec_busy_polling || bits > 8)
                acpi_ec_burst_enable(ec);

        for (i = 0; i < bytes; ++i, ++address, ++value)
                result = (function == ACPI_READ) ?
                        acpi_ec_read(ec, address, value) :
                        acpi_ec_write(ec, address, *value);

        if (ec_busy_polling || bits > 8)
                acpi_ec_burst_disable(ec);

        switch (result) {
        case -EINVAL:
                return AE_BAD_PARAMETER;
        case -ENODEV:
                return AE_NOT_FOUND;
        case -ETIME:
                return AE_TIME;
        default:
                return AE_OK;
        }
}

/* --------------------------------------------------------------------------
 *                             Driver Interface
 * -------------------------------------------------------------------------- */

static acpi_status
ec_parse_io_ports(struct acpi_resource *resource, void *context);

static struct acpi_ec *make_acpi_ec(void)
{
        struct acpi_ec *ec = kzalloc(sizeof(struct acpi_ec), GFP_KERNEL);

        if (!ec)
                return NULL;
        ec->flags = 1 << EC_FLAGS_QUERY_PENDING;
        mutex_init(&ec->mutex);
        init_waitqueue_head(&ec->wait);
        INIT_LIST_HEAD(&ec->list);
        spin_lock_init(&ec->lock);
        INIT_WORK(&ec->work, acpi_ec_event_handler);
        ec->timestamp = jiffies;
        return ec;
}

static acpi_status
acpi_ec_register_query_methods(acpi_handle handle, u32 level,
                               void *context, void **return_value)
{
        char node_name[5];
        struct acpi_buffer buffer = { sizeof(node_name), node_name };
        struct acpi_ec *ec = context;
        int value = 0;
        acpi_status status;

        status = acpi_get_name(handle, ACPI_SINGLE_NAME, &buffer);

        if (ACPI_SUCCESS(status) && sscanf(node_name, "_Q%x", &value) == 1)
                acpi_ec_add_query_handler(ec, value, handle, NULL, NULL);
        return AE_OK;
}

static acpi_status
ec_parse_device(acpi_handle handle, u32 Level, void *context, void **retval)
{
        acpi_status status;
        unsigned long long tmp = 0;
        struct acpi_ec *ec = context;

        /* clear addr values, ec_parse_io_ports depend on it */
        ec->command_addr = ec->data_addr = 0;

        status = acpi_walk_resources(handle, METHOD_NAME__CRS,
                                     ec_parse_io_ports, ec);
        if (ACPI_FAILURE(status))
                return status;

        /* Get GPE bit assignment (EC events). */
        /* TODO: Add support for _GPE returning a package */
        status = acpi_evaluate_integer(handle, "_GPE", NULL, &tmp);
        if (ACPI_FAILURE(status))
                return status;
        ec->gpe = tmp;
        /* Use the global lock for all EC transactions? */
        tmp = 0;
        acpi_evaluate_integer(handle, "_GLK", NULL, &tmp);
        ec->global_lock = tmp;
        ec->handle = handle;
        return AE_CTRL_TERMINATE;
}

static int ec_install_handlers(struct acpi_ec *ec)
{
        acpi_status status;

        acpi_ec_start(ec, false);

        if (!test_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags)) {
                status = acpi_install_address_space_handler(ec->handle,
                                                            ACPI_ADR_SPACE_EC,
                                                            &acpi_ec_space_handler,
                                                            NULL, ec);
                if (ACPI_FAILURE(status)) {
                        if (status == AE_NOT_FOUND) {
                                /*
                                 * Maybe OS fails in evaluating the _REG
                                 * object. The AE_NOT_FOUND error will be
                                 * ignored and OS * continue to initialize
                                 * EC.
                                 */
                                pr_err("Fail in evaluating the _REG object"
                                        " of EC device. Broken bios is suspected.\n");
                        } else {
                                acpi_ec_stop(ec, false);
                                return -ENODEV;
                        }
                }
                set_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags);
        }

        if (!test_bit(EC_FLAGS_GPE_HANDLER_INSTALLED, &ec->flags)) {
                status = acpi_install_gpe_raw_handler(NULL, ec->gpe,
                                          ACPI_GPE_EDGE_TRIGGERED,
                                          &acpi_ec_gpe_handler, ec);
                /* This is not fatal as we can poll EC events */
                if (ACPI_SUCCESS(status)) {
                        set_bit(EC_FLAGS_GPE_HANDLER_INSTALLED, &ec->flags);
                        if (test_bit(EC_FLAGS_STARTED, &ec->flags) &&
                            ec->reference_count >= 1)
                                acpi_ec_enable_gpe(ec, true);
                }
        }

        return 0;
}

static void ec_remove_handlers(struct acpi_ec *ec)
{
        if (test_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags)) {
                if (ACPI_FAILURE(acpi_remove_address_space_handler(ec->handle,
                                        ACPI_ADR_SPACE_EC, &acpi_ec_space_handler)))
                        pr_err("failed to remove space handler\n");
                clear_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags);
        }

        /*
         * Stops handling the EC transactions after removing the operation
         * region handler. This is required because _REG(DISCONNECT)
         * invoked during the removal can result in new EC transactions.
         *
         * Flushes the EC requests and thus disables the GPE before
         * removing the GPE handler. This is required by the current ACPICA
         * GPE core. ACPICA GPE core will automatically disable a GPE when
         * it is indicated but there is no way to handle it. So the drivers
         * must disable the GPEs prior to removing the GPE handlers.
         */
        acpi_ec_stop(ec, false);

        if (test_bit(EC_FLAGS_GPE_HANDLER_INSTALLED, &ec->flags)) {
                if (ACPI_FAILURE(acpi_remove_gpe_handler(NULL, ec->gpe,
                                        &acpi_ec_gpe_handler)))
                        pr_err("failed to remove gpe handler\n");
                clear_bit(EC_FLAGS_GPE_HANDLER_INSTALLED, &ec->flags);
        }
}

static struct acpi_ec *acpi_ec_alloc(void)
{
        struct acpi_ec *ec;

        /* Check for boot EC */
        if (boot_ec) {
                ec = boot_ec;
                boot_ec = NULL;
                ec_remove_handlers(ec);
                if (first_ec == ec)
                        first_ec = NULL;
        } else {
                ec = make_acpi_ec();
        }
        return ec;
}

static int acpi_ec_add(struct acpi_device *device)
{
        struct acpi_ec *ec = NULL;
        int ret;

        strcpy(acpi_device_name(device), ACPI_EC_DEVICE_NAME);
        strcpy(acpi_device_class(device), ACPI_EC_CLASS);

        ec = acpi_ec_alloc();
        if (!ec)
                return -ENOMEM;
        if (ec_parse_device(device->handle, 0, ec, NULL) !=
                AE_CTRL_TERMINATE) {
                        kfree(ec);
                        return -EINVAL;
        }

        /* Find and register all query methods */
        acpi_walk_namespace(ACPI_TYPE_METHOD, ec->handle, 1,
                            acpi_ec_register_query_methods, NULL, ec, NULL);

        if (!first_ec)
                first_ec = ec;
        device->driver_data = ec;

        ret = !!request_region(ec->data_addr, 1, "EC data");
        WARN(!ret, "Could not request EC data io port 0x%lx", ec->data_addr);
        ret = !!request_region(ec->command_addr, 1, "EC cmd");
        WARN(!ret, "Could not request EC cmd io port 0x%lx", ec->command_addr);

        pr_info("GPE = 0x%lx, I/O: command/status = 0x%lx, data = 0x%lx\n",
                          ec->gpe, ec->command_addr, ec->data_addr);

        ret = ec_install_handlers(ec);

        /* Reprobe devices depending on the EC */
        acpi_walk_dep_device_list(ec->handle);

        /* EC is fully operational, allow queries */
        clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);

        /* Clear stale _Q events if hardware might require that */
        if (EC_FLAGS_CLEAR_ON_RESUME)
                acpi_ec_clear(ec);
        return ret;
}

static int acpi_ec_remove(struct acpi_device *device)
{
        struct acpi_ec *ec;

        if (!device)
                return -EINVAL;

        ec = acpi_driver_data(device);
        ec_remove_handlers(ec);
        acpi_ec_remove_query_handlers(ec, true, 0);
        release_region(ec->data_addr, 1);
        release_region(ec->command_addr, 1);
        device->driver_data = NULL;
        if (ec == first_ec)
                first_ec = NULL;
        kfree(ec);
        return 0;
}

static acpi_status
ec_parse_io_ports(struct acpi_resource *resource, void *context)
{
        struct acpi_ec *ec = context;

        if (resource->type != ACPI_RESOURCE_TYPE_IO)
                return AE_OK;

        /*
         * The first address region returned is the data port, and
         * the second address region returned is the status/command
         * port.
         */
        if (ec->data_addr == 0)
                ec->data_addr = resource->data.io.minimum;
        else if (ec->command_addr == 0)
                ec->command_addr = resource->data.io.minimum;
        else
                return AE_CTRL_TERMINATE;

        return AE_OK;
}

static const struct acpi_device_id ec_device_ids[] = {
        {"PNP0C09", 0},
        {"", 0},
};

int __init acpi_ec_dsdt_probe(void)
{
        acpi_status status;
        struct acpi_ec *ec;
        int ret;

        ec = acpi_ec_alloc();
        if (!ec)
                return -ENOMEM;
        /*
         * Finding EC from DSDT if there is no ECDT EC available. When this
         * function is invoked, ACPI tables have been fully loaded, we can
         * walk namespace now.
         */
        status = acpi_get_devices(ec_device_ids[0].id,
                                  ec_parse_device, ec, NULL);
        if (ACPI_FAILURE(status) || !ec->handle) {
                ret = -ENODEV;
                goto error;
        }
        ret = ec_install_handlers(ec);

error:
        if (ret)
                kfree(ec);
        else
                first_ec = boot_ec = ec;
        return ret;
}

#if 0
/*
 * Some EC firmware variations refuses to respond QR_EC when SCI_EVT is not
 * set, for which case, we complete the QR_EC without issuing it to the
 * firmware.
 * https://bugzilla.kernel.org/show_bug.cgi?id=82611
 * https://bugzilla.kernel.org/show_bug.cgi?id=97381
 */
static int ec_flag_query_handshake(const struct dmi_system_id *id)
{
        pr_debug("Detected the EC firmware requiring QR_EC issued when SCI_EVT set\n");
        EC_FLAGS_QUERY_HANDSHAKE = 1;
        return 0;
}
#endif

/*
 * On some hardware it is necessary to clear events accumulated by the EC during
 * sleep. These ECs stop reporting GPEs until they are manually polled, if too
 * many events are accumulated. (e.g. Samsung Series 5/9 notebooks)
 *
 * https://bugzilla.kernel.org/show_bug.cgi?id=44161
 *
 * Ideally, the EC should also be instructed NOT to accumulate events during
 * sleep (which Windows seems to do somehow), but the interface to control this
 * behaviour is not known at this time.
 *
 * Models known to be affected are Samsung 530Uxx/535Uxx/540Uxx/550Pxx/900Xxx,
 * however it is very likely that other Samsung models are affected.
 *
 * On systems which don't accumulate _Q events during sleep, this extra check
 * should be harmless.
 */
static int ec_clear_on_resume(const struct dmi_system_id *id)
{
        pr_debug("Detected system needing EC poll on resume.\n");
        EC_FLAGS_CLEAR_ON_RESUME = 1;
        ec_event_clearing = ACPI_EC_EVT_TIMING_STATUS;
        return 0;
}

/*
 * Some ECDTs contain wrong register addresses.
 * MSI MS-171F
 * https://bugzilla.kernel.org/show_bug.cgi?id=12461
 */
static int ec_correct_ecdt(const struct dmi_system_id *id)
{
        pr_debug("Detected system needing ECDT address correction.\n");
        EC_FLAGS_CORRECT_ECDT = 1;
        return 0;
}

static struct dmi_system_id ec_dmi_table[] __initdata = {
        {
        ec_correct_ecdt, "MSI MS-171F", {
        DMI_MATCH(DMI_SYS_VENDOR, "Micro-Star"),
        DMI_MATCH(DMI_PRODUCT_NAME, "MS-171F"),}, NULL},
        {
        ec_clear_on_resume, "Samsung hardware", {
        DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD.")}, NULL},
        {},
};

int __init acpi_ec_ecdt_probe(void)
{
        int ret;
        acpi_status status;
        struct acpi_table_ecdt *ecdt_ptr;
        struct acpi_ec *ec;

        ec = acpi_ec_alloc();
        if (!ec)
                return -ENOMEM;
        /*
         * Generate a boot ec context
         */
        dmi_check_system(ec_dmi_table);
        status = acpi_get_table(ACPI_SIG_ECDT, 1,
                                (struct acpi_table_header **)&ecdt_ptr);
        if (ACPI_FAILURE(status)) {
                ret = -ENODEV;
                goto error;
        }

        if (!ecdt_ptr->control.address || !ecdt_ptr->data.address) {
                /*
                 * Asus X50GL:
                 * https://bugzilla.kernel.org/show_bug.cgi?id=11880
                 */
                ret = -ENODEV;
                goto error;
        }

        pr_info("EC description table is found, configuring boot EC\n");
        if (EC_FLAGS_CORRECT_ECDT) {
                ec->command_addr = ecdt_ptr->data.address;
                ec->data_addr = ecdt_ptr->control.address;
        } else {
                ec->command_addr = ecdt_ptr->control.address;
                ec->data_addr = ecdt_ptr->data.address;
        }
        ec->gpe = ecdt_ptr->gpe;
        ec->handle = ACPI_ROOT_OBJECT;
        ret = ec_install_handlers(ec);
error:
        if (ret)
                kfree(ec);
        else
                first_ec = boot_ec = ec;
        return ret;
}

static int param_set_event_clearing(const char *val, struct kernel_param *kp)
{
        int result = 0;

        if (!strncmp(val, "status", sizeof("status") - 1)) {
                ec_event_clearing = ACPI_EC_EVT_TIMING_STATUS;
                pr_info("Assuming SCI_EVT clearing on EC_SC accesses\n");
        } else if (!strncmp(val, "query", sizeof("query") - 1)) {
                ec_event_clearing = ACPI_EC_EVT_TIMING_QUERY;
                pr_info("Assuming SCI_EVT clearing on QR_EC writes\n");
        } else if (!strncmp(val, "event", sizeof("event") - 1)) {
                ec_event_clearing = ACPI_EC_EVT_TIMING_EVENT;
                pr_info("Assuming SCI_EVT clearing on event reads\n");
        } else
                result = -EINVAL;
        return result;
}

static int param_get_event_clearing(char *buffer, struct kernel_param *kp)
{
        switch (ec_event_clearing) {
        case ACPI_EC_EVT_TIMING_STATUS:
                return sprintf(buffer, "status");
        case ACPI_EC_EVT_TIMING_QUERY:
                return sprintf(buffer, "query");
        case ACPI_EC_EVT_TIMING_EVENT:
                return sprintf(buffer, "event");
        default:
                return sprintf(buffer, "invalid");
        }
        return 0;
}

module_param_call(ec_event_clearing, param_set_event_clearing, param_get_event_clearing,
                  NULL, 0644);
MODULE_PARM_DESC(ec_event_clearing, "Assumed SCI_EVT clearing timing");

static struct acpi_driver acpi_ec_driver = {
        .name = "ec",
        .class = ACPI_EC_CLASS,
        .ids = ec_device_ids,
        .ops = {
                .add = acpi_ec_add,
                .remove = acpi_ec_remove,
                },
};

static inline int acpi_ec_query_init(void)
{
        if (!ec_query_wq) {
                ec_query_wq = alloc_workqueue("kec_query", 0,
                                              ec_max_queries);
                if (!ec_query_wq)
                        return -ENODEV;
        }
        return 0;
}

static inline void acpi_ec_query_exit(void)
{
        if (ec_query_wq) {
                destroy_workqueue(ec_query_wq);
                ec_query_wq = NULL;
        }
}

int __init acpi_ec_init(void)
{
        int result;

        /* register workqueue for _Qxx evaluations */
        result = acpi_ec_query_init();
        if (result)
                goto err_exit;
        /* Now register the driver for the EC */
        result = acpi_bus_register_driver(&acpi_ec_driver);
        if (result)
                goto err_exit;

err_exit:
        if (result)
                acpi_ec_query_exit();
        return result;
}

/* EC driver currently not unloadable */
#if 0
static void __exit acpi_ec_exit(void)
{

        acpi_bus_unregister_driver(&acpi_ec_driver);
        acpi_ec_query_exit();
}
#endif  /* 0 */