// SPDX-License-Identifier: GPL-2.0
/*
 * System Control and Management Interface (SCMI) Message Mailbox Transport
 * driver.
 *
 * Copyright (C) 2019 ARM Ltd.
 */

#include <linux/err.h>
#include <linux/device.h>
#include <linux/mailbox_client.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/slab.h>

#include "common.h"

/**
 * struct scmi_mailbox - Structure representing a SCMI mailbox transport
 *
 * @cl: Mailbox Client
 * @chan: Transmit/Receive mailbox channel
 * @cinfo: SCMI channel info
 * @shmem: Transmit/Receive shared memory area
 */
struct scmi_mailbox {
        struct mbox_client cl;
        struct mbox_chan *chan;
        struct scmi_chan_info *cinfo;
        struct scmi_shared_mem __iomem *shmem;
};

#define client_to_scmi_mailbox(c) container_of(c, struct scmi_mailbox, cl)

static void tx_prepare(struct mbox_client *cl, void *m)
{
        struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);

        shmem_tx_prepare(smbox->shmem, m);
}

static void rx_callback(struct mbox_client *cl, void *m)
{
        struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);

        scmi_rx_callback(smbox->cinfo, shmem_read_header(smbox->shmem));
}

static bool mailbox_chan_available(struct device *dev, int idx)
{
        return !of_parse_phandle_with_args(dev->of_node, "mboxes",
                                           "#mbox-cells", idx, NULL);
}

static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
                              bool tx)
{
        const char *desc = tx ? "Tx" : "Rx";
        struct device *cdev = cinfo->dev;
        struct scmi_mailbox *smbox;
        struct device_node *shmem;
        int ret, idx = tx ? 0 : 1;
        struct mbox_client *cl;
        resource_size_t size;
        struct resource res;

        smbox = devm_kzalloc(dev, sizeof(*smbox), GFP_KERNEL);
        if (!smbox)
                return -ENOMEM;

        shmem = of_parse_phandle(cdev->of_node, "shmem", idx);
        ret = of_address_to_resource(shmem, 0, &res);
        of_node_put(shmem);
        if (ret) {
                dev_err(cdev, "failed to get SCMI %s shared memory\n", desc);
                return ret;
        }

        size = resource_size(&res);
        smbox->shmem = devm_ioremap(dev, res.start, size);
        if (!smbox->shmem) {
                dev_err(dev, "failed to ioremap SCMI %s shared memory\n", desc);
                return -EADDRNOTAVAIL;
        }

        cl = &smbox->cl;
        cl->dev = cdev;
        cl->tx_prepare = tx ? tx_prepare : NULL;
        cl->rx_callback = rx_callback;
        cl->tx_block = false;
        cl->knows_txdone = tx;

        smbox->chan = mbox_request_channel(cl, tx ? 0 : 1);
        if (IS_ERR(smbox->chan)) {
                ret = PTR_ERR(smbox->chan);
                if (ret != -EPROBE_DEFER)
                        dev_err(cdev, "failed to request SCMI %s mailbox\n",
                                tx ? "Tx" : "Rx");
                return ret;
        }

        cinfo->transport_info = smbox;
        smbox->cinfo = cinfo;

        return 0;
}

static int mailbox_chan_free(int id, void *p, void *data)
{
        struct scmi_chan_info *cinfo = p;
        struct scmi_mailbox *smbox = cinfo->transport_info;

        if (!IS_ERR(smbox->chan)) {
                mbox_free_channel(smbox->chan);
                cinfo->transport_info = NULL;
                smbox->chan = NULL;
                smbox->cinfo = NULL;
        }

        scmi_free_channel(cinfo, data, id);

        return 0;
}

static int mailbox_send_message(struct scmi_chan_info *cinfo,
                                struct scmi_xfer *xfer)
{
        struct scmi_mailbox *smbox = cinfo->transport_info;
        int ret;

        ret = mbox_send_message(smbox->chan, xfer);

        /* mbox_send_message returns non-negative value on success, so reset */
        if (ret > 0)
                ret = 0;

        return ret;
}

static void mailbox_mark_txdone(struct scmi_chan_info *cinfo, int ret)
{
        struct scmi_mailbox *smbox = cinfo->transport_info;

        /*
         * NOTE: we might prefer not to need the mailbox ticker to manage the
         * transfer queueing since the protocol layer queues things by itself.
         * Unfortunately, we have to kick the mailbox framework after we have
         * received our message.
         */
        mbox_client_txdone(smbox->chan, ret);
}

static void mailbox_fetch_response(struct scmi_chan_info *cinfo,
                                   struct scmi_xfer *xfer)
{
        struct scmi_mailbox *smbox = cinfo->transport_info;

        shmem_fetch_response(smbox->shmem, xfer);
}

static void mailbox_fetch_notification(struct scmi_chan_info *cinfo,
                                       size_t max_len, struct scmi_xfer *xfer)
{
        struct scmi_mailbox *smbox = cinfo->transport_info;

        shmem_fetch_notification(smbox->shmem, max_len, xfer);
}

static void mailbox_clear_channel(struct scmi_chan_info *cinfo)
{
        struct scmi_mailbox *smbox = cinfo->transport_info;

        shmem_clear_channel(smbox->shmem);
}

static bool
mailbox_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
{
        struct scmi_mailbox *smbox = cinfo->transport_info;

        return shmem_poll_done(smbox->shmem, xfer);
}

static struct scmi_transport_ops scmi_mailbox_ops = {
        .chan_available = mailbox_chan_available,
        .chan_setup = mailbox_chan_setup,
        .chan_free = mailbox_chan_free,
        .send_message = mailbox_send_message,
        .mark_txdone = mailbox_mark_txdone,
        .fetch_response = mailbox_fetch_response,
        .fetch_notification = mailbox_fetch_notification,
        .clear_channel = mailbox_clear_channel,
        .poll_done = mailbox_poll_done,
};

const struct scmi_desc scmi_mailbox_desc = {
        .ops = &scmi_mailbox_ops,
        .max_rx_timeout_ms = 30, /* We may increase this if required */
        .max_msg = 20, /* Limited by MBOX_TX_QUEUE_LEN */
        .max_msg_size = 128,
};