/*
 * PowerNV OPAL asynchronous completion interfaces
 *
 * Copyright 2013 IBM Corp.
 *
 * 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.
 */

#undef DEBUG

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/semaphore.h>
#include <linux/spinlock.h>
#include <linux/wait.h>
#include <linux/gfp.h>
#include <linux/of.h>
#include <asm/machdep.h>
#include <asm/opal.h>

#define N_ASYNC_COMPLETIONS     64

static DECLARE_BITMAP(opal_async_complete_map, N_ASYNC_COMPLETIONS) = {~0UL};
static DECLARE_BITMAP(opal_async_token_map, N_ASYNC_COMPLETIONS);
static DECLARE_WAIT_QUEUE_HEAD(opal_async_wait);
static DEFINE_SPINLOCK(opal_async_comp_lock);
static struct semaphore opal_async_sem;
static struct opal_msg *opal_async_responses;
static unsigned int opal_max_async_tokens;

int __opal_async_get_token(void)
{
        unsigned long flags;
        int token;

        spin_lock_irqsave(&opal_async_comp_lock, flags);
        token = find_first_bit(opal_async_complete_map, opal_max_async_tokens);
        if (token >= opal_max_async_tokens) {
                token = -EBUSY;
                goto out;
        }

        if (__test_and_set_bit(token, opal_async_token_map)) {
                token = -EBUSY;
                goto out;
        }

        __clear_bit(token, opal_async_complete_map);

out:
        spin_unlock_irqrestore(&opal_async_comp_lock, flags);
        return token;
}

int opal_async_get_token_interruptible(void)
{
        int token;

        /* Wait until a token is available */
        if (down_interruptible(&opal_async_sem))
                return -ERESTARTSYS;

        token = __opal_async_get_token();
        if (token < 0)
                up(&opal_async_sem);

        return token;
}
EXPORT_SYMBOL_GPL(opal_async_get_token_interruptible);

int __opal_async_release_token(int token)
{
        unsigned long flags;

        if (token < 0 || token >= opal_max_async_tokens) {
                pr_err("%s: Passed token is out of range, token %d\n",
                                __func__, token);
                return -EINVAL;
        }

        spin_lock_irqsave(&opal_async_comp_lock, flags);
        __set_bit(token, opal_async_complete_map);
        __clear_bit(token, opal_async_token_map);
        spin_unlock_irqrestore(&opal_async_comp_lock, flags);

        return 0;
}

int opal_async_release_token(int token)
{
        int ret;

        ret = __opal_async_release_token(token);
        if (ret)
                return ret;

        up(&opal_async_sem);

        return 0;
}
EXPORT_SYMBOL_GPL(opal_async_release_token);

int opal_async_wait_response(uint64_t token, struct opal_msg *msg)
{
        if (token >= opal_max_async_tokens) {
                pr_err("%s: Invalid token passed\n", __func__);
                return -EINVAL;
        }

        if (!msg) {
                pr_err("%s: Invalid message pointer passed\n", __func__);
                return -EINVAL;
        }

        /* Wakeup the poller before we wait for events to speed things
         * up on platforms or simulators where the interrupts aren't
         * functional.
         */
        opal_wake_poller();
        wait_event(opal_async_wait, test_bit(token, opal_async_complete_map));
        memcpy(msg, &opal_async_responses[token], sizeof(*msg));

        return 0;
}
EXPORT_SYMBOL_GPL(opal_async_wait_response);

static int opal_async_comp_event(struct notifier_block *nb,
                unsigned long msg_type, void *msg)
{
        struct opal_msg *comp_msg = msg;
        unsigned long flags;
        uint64_t token;

        if (msg_type != OPAL_MSG_ASYNC_COMP)
                return 0;

        token = be64_to_cpu(comp_msg->params[0]);
        memcpy(&opal_async_responses[token], comp_msg, sizeof(*comp_msg));
        spin_lock_irqsave(&opal_async_comp_lock, flags);
        __set_bit(token, opal_async_complete_map);
        spin_unlock_irqrestore(&opal_async_comp_lock, flags);

        wake_up(&opal_async_wait);

        return 0;
}

static struct notifier_block opal_async_comp_nb = {
                .notifier_call  = opal_async_comp_event,
                .next           = NULL,
                .priority       = 0,
};

int __init opal_async_comp_init(void)
{
        struct device_node *opal_node;
        const __be32 *async;
        int err;

        opal_node = of_find_node_by_path("/ibm,opal");
        if (!opal_node) {
                pr_err("%s: Opal node not found\n", __func__);
                err = -ENOENT;
                goto out;
        }

        async = of_get_property(opal_node, "opal-msg-async-num", NULL);
        if (!async) {
                pr_err("%s: %s has no opal-msg-async-num\n",
                                __func__, opal_node->full_name);
                err = -ENOENT;
                goto out_opal_node;
        }

        opal_max_async_tokens = be32_to_cpup(async);
        if (opal_max_async_tokens > N_ASYNC_COMPLETIONS)
                opal_max_async_tokens = N_ASYNC_COMPLETIONS;

        err = opal_message_notifier_register(OPAL_MSG_ASYNC_COMP,
                        &opal_async_comp_nb);
        if (err) {
                pr_err("%s: Can't register OPAL event notifier (%d)\n",
                                __func__, err);
                goto out_opal_node;
        }

        opal_async_responses = kzalloc(
                        sizeof(*opal_async_responses) * opal_max_async_tokens,
                        GFP_KERNEL);
        if (!opal_async_responses) {
                pr_err("%s: Out of memory, failed to do asynchronous "
                                "completion init\n", __func__);
                err = -ENOMEM;
                goto out_opal_node;
        }

        /* Initialize to 1 less than the maximum tokens available, as we may
         * require to pop one during emergency through synchronous call to
         * __opal_async_get_token()
         */
        sema_init(&opal_async_sem, opal_max_async_tokens - 1);

out_opal_node:
        of_node_put(opal_node);
out:
        return err;
}