// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright Aspeed Technology Inc. (C) 2025. All rights reserved
 */

#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/kernel.h>
#include <linux/mailbox_controller.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

/* Each bit in the register represents an IPC ID */
#define IPCR_TX_TRIG            0x00
#define IPCR_ENABLE             0x04
#define IPCR_STATUS             0x08
#define  RX_IRQ(n)              BIT(n)
#define  RX_IRQ_MASK            0xf
#define IPCR_DATA               0x10

struct ast2700_mbox_data {
        u8 num_chans;
        u8 msg_size;
};

struct ast2700_mbox {
        struct mbox_controller mbox;
        u8 msg_size;
        void __iomem *tx_regs;
        void __iomem *rx_regs;
        spinlock_t lock;
};

static inline int ch_num(struct mbox_chan *chan)
{
        return chan - chan->mbox->chans;
}

static inline bool ast2700_mbox_tx_done(struct ast2700_mbox *mb, int idx)
{
        return !(readl(mb->tx_regs + IPCR_STATUS) & BIT(idx));
}

static irqreturn_t ast2700_mbox_irq(int irq, void *p)
{
        struct ast2700_mbox *mb = p;
        void __iomem *data_reg;
        int num_words = mb->msg_size / sizeof(u32);
        u32 *word_data;
        u32 status;
        int n, i;

        /* Only examine channels that are currently enabled. */
        status = readl(mb->rx_regs + IPCR_ENABLE) &
                 readl(mb->rx_regs + IPCR_STATUS);

        if (!(status & RX_IRQ_MASK))
                return IRQ_NONE;

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

                if (!(status & RX_IRQ(n)))
                        continue;

                data_reg = mb->rx_regs + IPCR_DATA + mb->msg_size * n;
                word_data = chan->con_priv;
                /* Read the message data */
                for (i = 0; i < num_words; i++)
                        word_data[i] = readl(data_reg + i * sizeof(u32));

                mbox_chan_received_data(chan, chan->con_priv);

                /* The IRQ can be cleared only once the FIFO is empty. */
                writel(RX_IRQ(n), mb->rx_regs + IPCR_STATUS);
        }

        return IRQ_HANDLED;
}

static int ast2700_mbox_send_data(struct mbox_chan *chan, void *data)
{
        struct ast2700_mbox *mb = dev_get_drvdata(chan->mbox->dev);
        int idx = ch_num(chan);
        void __iomem *data_reg = mb->tx_regs + IPCR_DATA + mb->msg_size * idx;
        u32 *word_data = data;
        int num_words = mb->msg_size / sizeof(u32);
        int i;

        if (!(readl(mb->tx_regs + IPCR_ENABLE) & BIT(idx))) {
                dev_warn(mb->mbox.dev, "%s: Ch-%d not enabled yet\n", __func__, idx);
                return -ENODEV;
        }

        if (!(ast2700_mbox_tx_done(mb, idx))) {
                dev_warn(mb->mbox.dev, "%s: Ch-%d last data has not finished\n", __func__, idx);
                return -EBUSY;
        }

        /* Write the message data */
        for (i = 0 ; i < num_words; i++)
                writel(word_data[i], data_reg + i * sizeof(u32));

        writel(BIT(idx), mb->tx_regs + IPCR_TX_TRIG);
        dev_dbg(mb->mbox.dev, "%s: Ch-%d sent\n", __func__, idx);

        return 0;
}

static int ast2700_mbox_startup(struct mbox_chan *chan)
{
        struct ast2700_mbox *mb = dev_get_drvdata(chan->mbox->dev);
        int idx = ch_num(chan);
        void __iomem *reg = mb->rx_regs + IPCR_ENABLE;
        unsigned long flags;

        spin_lock_irqsave(&mb->lock, flags);
        writel(readl(reg) | BIT(idx), reg);
        spin_unlock_irqrestore(&mb->lock, flags);

        return 0;
}

static void ast2700_mbox_shutdown(struct mbox_chan *chan)
{
        struct ast2700_mbox *mb = dev_get_drvdata(chan->mbox->dev);
        int idx = ch_num(chan);
        void __iomem *reg = mb->rx_regs + IPCR_ENABLE;
        unsigned long flags;

        spin_lock_irqsave(&mb->lock, flags);
        writel(readl(reg) & ~BIT(idx), reg);
        spin_unlock_irqrestore(&mb->lock, flags);
}

static bool ast2700_mbox_last_tx_done(struct mbox_chan *chan)
{
        struct ast2700_mbox *mb = dev_get_drvdata(chan->mbox->dev);
        int idx = ch_num(chan);

        return ast2700_mbox_tx_done(mb, idx);
}

static const struct mbox_chan_ops ast2700_mbox_chan_ops = {
        .send_data      = ast2700_mbox_send_data,
        .startup        = ast2700_mbox_startup,
        .shutdown       = ast2700_mbox_shutdown,
        .last_tx_done   = ast2700_mbox_last_tx_done,
};

static int ast2700_mbox_probe(struct platform_device *pdev)
{
        struct ast2700_mbox *mb;
        const struct ast2700_mbox_data *dev_data;
        struct device *dev = &pdev->dev;
        int irq, ret;

        if (!pdev->dev.of_node)
                return -ENODEV;

        dev_data = device_get_match_data(&pdev->dev);

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

        mb->mbox.chans = devm_kcalloc(&pdev->dev, dev_data->num_chans,
                                      sizeof(*mb->mbox.chans), GFP_KERNEL);
        if (!mb->mbox.chans)
                return -ENOMEM;

        /* con_priv of each channel is used to store the message received */
        for (int i = 0; i < dev_data->num_chans; i++) {
                mb->mbox.chans[i].con_priv = devm_kcalloc(dev, dev_data->msg_size,
                                                          sizeof(u8), GFP_KERNEL);
                if (!mb->mbox.chans[i].con_priv)
                        return -ENOMEM;
        }

        platform_set_drvdata(pdev, mb);

        mb->tx_regs = devm_platform_ioremap_resource_byname(pdev, "tx");
        if (IS_ERR(mb->tx_regs))
                return PTR_ERR(mb->tx_regs);

        mb->rx_regs = devm_platform_ioremap_resource_byname(pdev, "rx");
        if (IS_ERR(mb->rx_regs))
                return PTR_ERR(mb->rx_regs);

        mb->msg_size = dev_data->msg_size;
        mb->mbox.dev = dev;
        mb->mbox.num_chans = dev_data->num_chans;
        mb->mbox.ops = &ast2700_mbox_chan_ops;
        mb->mbox.txdone_irq = false;
        mb->mbox.txdone_poll = true;
        mb->mbox.txpoll_period = 5;
        spin_lock_init(&mb->lock);

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

        ret = devm_request_irq(dev, irq, ast2700_mbox_irq, 0, dev_name(dev), mb);
        if (ret)
                return ret;

        return devm_mbox_controller_register(dev, &mb->mbox);
}

static const struct ast2700_mbox_data ast2700_dev_data = {
        .num_chans = 4,
        .msg_size = 0x20,
};

static const struct of_device_id ast2700_mbox_of_match[] = {
        { .compatible = "aspeed,ast2700-mailbox", .data = &ast2700_dev_data },
        {}
};
MODULE_DEVICE_TABLE(of, ast2700_mbox_of_match);

static struct platform_driver ast2700_mbox_driver = {
        .driver = {
                .name = "ast2700-mailbox",
                .of_match_table = ast2700_mbox_of_match,
        },
        .probe = ast2700_mbox_probe,
};
module_platform_driver(ast2700_mbox_driver);

MODULE_AUTHOR("Jammy Huang <jammy_huang@aspeedtech.com>");
MODULE_DESCRIPTION("ASPEED AST2700 IPC driver");
MODULE_LICENSE("GPL");