/*
 * Mailbox: Common code for Mailbox controllers and users
 *
 * Copyright (C) 2013-2014 Linaro Ltd.
 * Author: Jassi Brar <jassisinghbrar@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/bitops.h>
#include <linux/mailbox_client.h>
#include <linux/mailbox_controller.h>

#include "mailbox.h"

static LIST_HEAD(mbox_cons);
static DEFINE_MUTEX(con_mutex);

static void poll_txdone(unsigned long data);

static int add_to_rbuf(struct mbox_chan *chan, void *mssg)
{
        int idx;
        unsigned long flags;

        spin_lock_irqsave(&chan->lock, flags);

        /* See if there is any space left */
        if (chan->msg_count == MBOX_TX_QUEUE_LEN) {
                spin_unlock_irqrestore(&chan->lock, flags);
                return -ENOBUFS;
        }

        idx = chan->msg_free;
        chan->msg_data[idx] = mssg;
        chan->msg_count++;

        if (idx == MBOX_TX_QUEUE_LEN - 1)
                chan->msg_free = 0;
        else
                chan->msg_free++;

        spin_unlock_irqrestore(&chan->lock, flags);

        return idx;
}

static void msg_submit(struct mbox_chan *chan)
{
        unsigned count, idx;
        unsigned long flags;
        void *data;
        int err = -EBUSY;

        spin_lock_irqsave(&chan->lock, flags);

        if (!chan->msg_count || chan->active_req)
                goto exit;

        count = chan->msg_count;
        idx = chan->msg_free;
        if (idx >= count)
                idx -= count;
        else
                idx += MBOX_TX_QUEUE_LEN - count;

        data = chan->msg_data[idx];

        if (chan->cl->tx_prepare)
                chan->cl->tx_prepare(chan->cl, data);
        /* Try to submit a message to the MBOX controller */
        err = chan->mbox->ops->send_data(chan, data);
        if (!err) {
                chan->active_req = data;
                chan->msg_count--;
        }
exit:
        spin_unlock_irqrestore(&chan->lock, flags);

        if (!err && (chan->txdone_method & TXDONE_BY_POLL))
                poll_txdone((unsigned long)chan->mbox);
}

static void tx_tick(struct mbox_chan *chan, int r)
{
        unsigned long flags;
        void *mssg;

        spin_lock_irqsave(&chan->lock, flags);
        mssg = chan->active_req;
        chan->active_req = NULL;
        spin_unlock_irqrestore(&chan->lock, flags);

        /* Submit next message */
        msg_submit(chan);

        /* Notify the client */
        if (mssg && chan->cl->tx_done)
                chan->cl->tx_done(chan->cl, mssg, r);

        if (chan->cl->tx_block)
                complete(&chan->tx_complete);
}

static void poll_txdone(unsigned long data)
{
        struct mbox_controller *mbox = (struct mbox_controller *)data;
        bool txdone, resched = false;
        int i;

        for (i = 0; i < mbox->num_chans; i++) {
                struct mbox_chan *chan = &mbox->chans[i];

                if (chan->active_req && chan->cl) {
                        txdone = chan->mbox->ops->last_tx_done(chan);
                        if (txdone)
                                tx_tick(chan, 0);
                        else
                                resched = true;
                }
        }

        if (resched)
                mod_timer(&mbox->poll, jiffies +
                                msecs_to_jiffies(mbox->txpoll_period));
}

/**
 * mbox_chan_received_data - A way for controller driver to push data
 *                              received from remote to the upper layer.
 * @chan: Pointer to the mailbox channel on which RX happened.
 * @mssg: Client specific message typecasted as void *
 *
 * After startup and before shutdown any data received on the chan
 * is passed on to the API via atomic mbox_chan_received_data().
 * The controller should ACK the RX only after this call returns.
 */
void mbox_chan_received_data(struct mbox_chan *chan, void *mssg)
{
        /* No buffering the received data */
        if (chan->cl->rx_callback)
                chan->cl->rx_callback(chan->cl, mssg);
}
EXPORT_SYMBOL_GPL(mbox_chan_received_data);

/**
 * mbox_chan_txdone - A way for controller driver to notify the
 *                      framework that the last TX has completed.
 * @chan: Pointer to the mailbox chan on which TX happened.
 * @r: Status of last TX - OK or ERROR
 *
 * The controller that has IRQ for TX ACK calls this atomic API
 * to tick the TX state machine. It works only if txdone_irq
 * is set by the controller.
 */
void mbox_chan_txdone(struct mbox_chan *chan, int r)
{
        if (unlikely(!(chan->txdone_method & TXDONE_BY_IRQ))) {
                dev_err(chan->mbox->dev,
                       "Controller can't run the TX ticker\n");
                return;
        }

        tx_tick(chan, r);
}
EXPORT_SYMBOL_GPL(mbox_chan_txdone);

/**
 * mbox_client_txdone - The way for a client to run the TX state machine.
 * @chan: Mailbox channel assigned to this client.
 * @r: Success status of last transmission.
 *
 * The client/protocol had received some 'ACK' packet and it notifies
 * the API that the last packet was sent successfully. This only works
 * if the controller can't sense TX-Done.
 */
void mbox_client_txdone(struct mbox_chan *chan, int r)
{
        if (unlikely(!(chan->txdone_method & TXDONE_BY_ACK))) {
                dev_err(chan->mbox->dev, "Client can't run the TX ticker\n");
                return;
        }

        tx_tick(chan, r);
}
EXPORT_SYMBOL_GPL(mbox_client_txdone);

/**
 * mbox_client_peek_data - A way for client driver to pull data
 *                      received from remote by the controller.
 * @chan: Mailbox channel assigned to this client.
 *
 * A poke to controller driver for any received data.
 * The data is actually passed onto client via the
 * mbox_chan_received_data()
 * The call can be made from atomic context, so the controller's
 * implementation of peek_data() must not sleep.
 *
 * Return: True, if controller has, and is going to push after this,
 *          some data.
 *         False, if controller doesn't have any data to be read.
 */
bool mbox_client_peek_data(struct mbox_chan *chan)
{
        if (chan->mbox->ops->peek_data)
                return chan->mbox->ops->peek_data(chan);

        return false;
}
EXPORT_SYMBOL_GPL(mbox_client_peek_data);

/**
 * mbox_send_message -  For client to submit a message to be
 *                              sent to the remote.
 * @chan: Mailbox channel assigned to this client.
 * @mssg: Client specific message typecasted.
 *
 * For client to submit data to the controller destined for a remote
 * processor. If the client had set 'tx_block', the call will return
 * either when the remote receives the data or when 'tx_tout' millisecs
 * run out.
 *  In non-blocking mode, the requests are buffered by the API and a
 * non-negative token is returned for each queued request. If the request
 * is not queued, a negative token is returned. Upon failure or successful
 * TX, the API calls 'tx_done' from atomic context, from which the client
 * could submit yet another request.
 * The pointer to message should be preserved until it is sent
 * over the chan, i.e, tx_done() is made.
 * This function could be called from atomic context as it simply
 * queues the data and returns a token against the request.
 *
 * Return: Non-negative integer for successful submission (non-blocking mode)
 *      or transmission over chan (blocking mode).
 *      Negative value denotes failure.
 */
int mbox_send_message(struct mbox_chan *chan, void *mssg)
{
        int t;

        if (!chan || !chan->cl)
                return -EINVAL;

        t = add_to_rbuf(chan, mssg);
        if (t < 0) {
                dev_err(chan->mbox->dev, "Try increasing MBOX_TX_QUEUE_LEN\n");
                return t;
        }

        msg_submit(chan);

        if (chan->cl->tx_block && chan->active_req) {
                unsigned long wait;
                int ret;

                if (!chan->cl->tx_tout) /* wait forever */
                        wait = msecs_to_jiffies(3600000);
                else
                        wait = msecs_to_jiffies(chan->cl->tx_tout);

                ret = wait_for_completion_timeout(&chan->tx_complete, wait);
                if (ret == 0) {
                        t = -EIO;
                        tx_tick(chan, -EIO);
                }
        }

        return t;
}
EXPORT_SYMBOL_GPL(mbox_send_message);

/**
 * mbox_request_channel - Request a mailbox channel.
 * @cl: Identity of the client requesting the channel.
 * @index: Index of mailbox specifier in 'mboxes' property.
 *
 * The Client specifies its requirements and capabilities while asking for
 * a mailbox channel. It can't be called from atomic context.
 * The channel is exclusively allocated and can't be used by another
 * client before the owner calls mbox_free_channel.
 * After assignment, any packet received on this channel will be
 * handed over to the client via the 'rx_callback'.
 * The framework holds reference to the client, so the mbox_client
 * structure shouldn't be modified until the mbox_free_channel returns.
 *
 * Return: Pointer to the channel assigned to the client if successful.
 *              ERR_PTR for request failure.
 */
struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index)
{
        struct device *dev = cl->dev;
        struct mbox_controller *mbox;
        struct of_phandle_args spec;
        struct mbox_chan *chan;
        unsigned long flags;
        int ret;

        if (!dev || !dev->of_node) {
                pr_debug("%s: No owner device node\n", __func__);
                return ERR_PTR(-ENODEV);
        }

        mutex_lock(&con_mutex);

        if (of_parse_phandle_with_args(dev->of_node, "mboxes",
                                       "#mbox-cells", index, &spec)) {
                dev_dbg(dev, "%s: can't parse \"mboxes\" property\n", __func__);
                mutex_unlock(&con_mutex);
                return ERR_PTR(-ENODEV);
        }

        chan = NULL;
        list_for_each_entry(mbox, &mbox_cons, node)
                if (mbox->dev->of_node == spec.np) {
                        chan = mbox->of_xlate(mbox, &spec);
                        break;
                }

        of_node_put(spec.np);

        if (!chan || chan->cl || !try_module_get(mbox->dev->driver->owner)) {
                dev_dbg(dev, "%s: mailbox not free\n", __func__);
                mutex_unlock(&con_mutex);
                return ERR_PTR(-EBUSY);
        }

        spin_lock_irqsave(&chan->lock, flags);
        chan->msg_free = 0;
        chan->msg_count = 0;
        chan->active_req = NULL;
        chan->cl = cl;
        init_completion(&chan->tx_complete);

        if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
                chan->txdone_method |= TXDONE_BY_ACK;

        spin_unlock_irqrestore(&chan->lock, flags);

        ret = chan->mbox->ops->startup(chan);
        if (ret) {
                dev_err(dev, "Unable to startup the chan (%d)\n", ret);
                mbox_free_channel(chan);
                chan = ERR_PTR(ret);
        }

        mutex_unlock(&con_mutex);
        return chan;
}
EXPORT_SYMBOL_GPL(mbox_request_channel);

/**
 * mbox_free_channel - The client relinquishes control of a mailbox
 *                      channel by this call.
 * @chan: The mailbox channel to be freed.
 */
void mbox_free_channel(struct mbox_chan *chan)
{
        unsigned long flags;

        if (!chan || !chan->cl)
                return;

        chan->mbox->ops->shutdown(chan);

        /* The queued TX requests are simply aborted, no callbacks are made */
        spin_lock_irqsave(&chan->lock, flags);
        chan->cl = NULL;
        chan->active_req = NULL;
        if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
                chan->txdone_method = TXDONE_BY_POLL;

        module_put(chan->mbox->dev->driver->owner);
        spin_unlock_irqrestore(&chan->lock, flags);
}
EXPORT_SYMBOL_GPL(mbox_free_channel);

static struct mbox_chan *
of_mbox_index_xlate(struct mbox_controller *mbox,
                    const struct of_phandle_args *sp)
{
        int ind = sp->args[0];

        if (ind >= mbox->num_chans)
                return NULL;

        return &mbox->chans[ind];
}

/**
 * mbox_controller_register - Register the mailbox controller
 * @mbox:       Pointer to the mailbox controller.
 *
 * The controller driver registers its communication channels
 */
int mbox_controller_register(struct mbox_controller *mbox)
{
        int i, txdone;

        /* Sanity check */
        if (!mbox || !mbox->dev || !mbox->ops || !mbox->num_chans)
                return -EINVAL;

        if (mbox->txdone_irq)
                txdone = TXDONE_BY_IRQ;
        else if (mbox->txdone_poll)
                txdone = TXDONE_BY_POLL;
        else /* It has to be ACK then */
                txdone = TXDONE_BY_ACK;

        if (txdone == TXDONE_BY_POLL) {
                mbox->poll.function = &poll_txdone;
                mbox->poll.data = (unsigned long)mbox;
                init_timer(&mbox->poll);
        }

        for (i = 0; i < mbox->num_chans; i++) {
                struct mbox_chan *chan = &mbox->chans[i];

                chan->cl = NULL;
                chan->mbox = mbox;
                chan->txdone_method = txdone;
                spin_lock_init(&chan->lock);
        }

        if (!mbox->of_xlate)
                mbox->of_xlate = of_mbox_index_xlate;

        mutex_lock(&con_mutex);
        list_add_tail(&mbox->node, &mbox_cons);
        mutex_unlock(&con_mutex);

        return 0;
}
EXPORT_SYMBOL_GPL(mbox_controller_register);

/**
 * mbox_controller_unregister - Unregister the mailbox controller
 * @mbox:       Pointer to the mailbox controller.
 */
void mbox_controller_unregister(struct mbox_controller *mbox)
{
        int i;

        if (!mbox)
                return;

        mutex_lock(&con_mutex);

        list_del(&mbox->node);

        for (i = 0; i < mbox->num_chans; i++)
                mbox_free_channel(&mbox->chans[i]);

        if (mbox->txdone_poll)
                del_timer_sync(&mbox->poll);

        mutex_unlock(&con_mutex);
}
EXPORT_SYMBOL_GPL(mbox_controller_unregister);