// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2013-2015 Fujitsu Semiconductor Ltd.
 * Copyright (C) 2015 Linaro Ltd.
 * Based on ARM MHU driver by Jassi Brar <jaswinder.singh@linaro.org>
 * Copyright (C) 2020 ARM Ltd.
 */

#include <linux/amba/bus.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/mailbox_controller.h>
#include <linux/module.h>
#include <linux/of.h>

#define INTR_STAT_OFS	0x0
#define INTR_SET_OFS	0x8
#define INTR_CLR_OFS	0x10

#define MHU_LP_OFFSET	0x0
#define MHU_HP_OFFSET	0x20
#define MHU_SEC_OFFSET	0x200
#define TX_REG_OFFSET	0x100

#define MHU_CHANS	3	/* Secure, Non-Secure High and Low Priority */
#define MHU_CHAN_MAX	20	/* Max channels to save on unused RAM */
#define MHU_NUM_DOORBELLS	32

struct mhu_db_link {
	unsigned int irq;
	void __iomem *tx_reg;
	void __iomem *rx_reg;
};

struct arm_mhu {
	void __iomem *base;
	struct mhu_db_link mlink[MHU_CHANS];
	struct mbox_controller mbox;
	struct device *dev;
};

/**
 * struct mhu_db_channel - ARM MHU Mailbox allocated channel information
 *
 * @mhu: Pointer to parent mailbox device
 * @pchan: Physical channel within which this doorbell resides in
 * @doorbell: doorbell number pertaining to this channel
 */
struct mhu_db_channel {
	struct arm_mhu *mhu;
	unsigned int pchan;
	unsigned int doorbell;
};

static inline struct mbox_chan *
mhu_db_mbox_to_channel(struct mbox_controller *mbox, unsigned int pchan,
		       unsigned int doorbell)
{
	int i;
	struct mhu_db_channel *chan_info;

	for (i = 0; i < mbox->num_chans; i++) {
		chan_info = mbox->chans[i].con_priv;
		if (chan_info && chan_info->pchan == pchan &&
		    chan_info->doorbell == doorbell)
			return &mbox->chans[i];
	}

	return NULL;
}

static void mhu_db_mbox_clear_irq(struct mbox_chan *chan)
{
	struct mhu_db_channel *chan_info = chan->con_priv;
	void __iomem *base = chan_info->mhu->mlink[chan_info->pchan].rx_reg;

	writel_relaxed(BIT(chan_info->doorbell), base + INTR_CLR_OFS);
}

static unsigned int mhu_db_mbox_irq_to_pchan_num(struct arm_mhu *mhu, int irq)
{
	unsigned int pchan;

	for (pchan = 0; pchan < MHU_CHANS; pchan++)
		if (mhu->mlink[pchan].irq == irq)
			break;
	return pchan;
}

static struct mbox_chan *
mhu_db_mbox_irq_to_channel(struct arm_mhu *mhu, unsigned int pchan)
{
	unsigned long bits;
	unsigned int doorbell;
	struct mbox_chan *chan = NULL;
	struct mbox_controller *mbox = &mhu->mbox;
	void __iomem *base = mhu->mlink[pchan].rx_reg;

	bits = readl_relaxed(base + INTR_STAT_OFS);
	if (!bits)
		/* No IRQs fired in specified physical channel */
		return NULL;

	/* An IRQ has fired, find the associated channel */
	for (doorbell = 0; bits; doorbell++) {
		if (!test_and_clear_bit(doorbell, &bits))
			continue;

		chan = mhu_db_mbox_to_channel(mbox, pchan, doorbell);
		if (chan)
			break;
		dev_err(mbox->dev,
			"Channel not registered: pchan: %d doorbell: %d\n",
			pchan, doorbell);
	}

	return chan;
}

static irqreturn_t mhu_db_mbox_rx_handler(int irq, void *data)
{
	struct mbox_chan *chan;
	struct arm_mhu *mhu = data;
	unsigned int pchan = mhu_db_mbox_irq_to_pchan_num(mhu, irq);

	while (NULL != (chan = mhu_db_mbox_irq_to_channel(mhu, pchan))) {
		mbox_chan_received_data(chan, NULL);
		mhu_db_mbox_clear_irq(chan);
	}

	return IRQ_HANDLED;
}

static bool mhu_db_last_tx_done(struct mbox_chan *chan)
{
	struct mhu_db_channel *chan_info = chan->con_priv;
	void __iomem *base = chan_info->mhu->mlink[chan_info->pchan].tx_reg;

	if (readl_relaxed(base + INTR_STAT_OFS) & BIT(chan_info->doorbell))
		return false;

	return true;
}

static int mhu_db_send_data(struct mbox_chan *chan, void *data)
{
	struct mhu_db_channel *chan_info = chan->con_priv;
	void __iomem *base = chan_info->mhu->mlink[chan_info->pchan].tx_reg;

	/* Send event to co-processor */
	writel_relaxed(BIT(chan_info->doorbell), base + INTR_SET_OFS);

	return 0;
}

static int mhu_db_startup(struct mbox_chan *chan)
{
	mhu_db_mbox_clear_irq(chan);
	return 0;
}

static void mhu_db_shutdown(struct mbox_chan *chan)
{
	struct mhu_db_channel *chan_info = chan->con_priv;
	struct mbox_controller *mbox = &chan_info->mhu->mbox;
	int i;

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

	if (mbox->num_chans == i) {
		dev_warn(mbox->dev, "Request to free non-existent channel\n");
		return;
	}

	/* Reset channel */
	mhu_db_mbox_clear_irq(chan);
	devm_kfree(mbox->dev, chan->con_priv);
	chan->con_priv = NULL;
}

static struct mbox_chan *mhu_db_mbox_xlate(struct mbox_controller *mbox,
					   const struct of_phandle_args *spec)
{
	struct arm_mhu *mhu = dev_get_drvdata(mbox->dev);
	struct mhu_db_channel *chan_info;
	struct mbox_chan *chan;
	unsigned int pchan = spec->args[0];
	unsigned int doorbell = spec->args[1];
	int i;

	/* Bounds checking */
	if (pchan >= MHU_CHANS || doorbell >= MHU_NUM_DOORBELLS) {
		dev_err(mbox->dev,
			"Invalid channel requested pchan: %d doorbell: %d\n",
			pchan, doorbell);
		return ERR_PTR(-EINVAL);
	}

	/* Is requested channel free? */
	chan = mhu_db_mbox_to_channel(mbox, pchan, doorbell);
	if (chan) {
		dev_err(mbox->dev, "Channel in use: pchan: %d doorbell: %d\n",
			pchan, doorbell);
		return ERR_PTR(-EBUSY);
	}

	/* Find the first free slot */
	for (i = 0; i < mbox->num_chans; i++)
		if (!mbox->chans[i].con_priv)
			break;

	if (mbox->num_chans == i) {
		dev_err(mbox->dev, "No free channels left\n");
		return ERR_PTR(-EBUSY);
	}

	chan = &mbox->chans[i];

	chan_info = devm_kzalloc(mbox->dev, sizeof(*chan_info), GFP_KERNEL);
	if (!chan_info)
		return ERR_PTR(-ENOMEM);

	chan_info->mhu = mhu;
	chan_info->pchan = pchan;
	chan_info->doorbell = doorbell;

	chan->con_priv = chan_info;

	dev_dbg(mbox->dev, "mbox: created channel phys: %d doorbell: %d\n",
		pchan, doorbell);

	return chan;
}

static const struct mbox_chan_ops mhu_db_ops = {
	.send_data = mhu_db_send_data,
	.startup = mhu_db_startup,
	.shutdown = mhu_db_shutdown,
	.last_tx_done = mhu_db_last_tx_done,
};

static int mhu_db_probe(struct amba_device *adev, const struct amba_id *id)
{
	u32 cell_count;
	int i, err, max_chans;
	struct arm_mhu *mhu;
	struct mbox_chan *chans;
	struct device *dev = &adev->dev;
	struct device_node *np = dev->of_node;
	int mhu_reg[MHU_CHANS] = {
		MHU_LP_OFFSET, MHU_HP_OFFSET, MHU_SEC_OFFSET,
	};

	if (!of_device_is_compatible(np, "arm,mhu-doorbell"))
		return -ENODEV;

	err = of_property_read_u32(np, "#mbox-cells", &cell_count);
	if (err) {
		dev_err(dev, "failed to read #mbox-cells in '%pOF'\n", np);
		return err;
	}

	if (cell_count == 2) {
		max_chans = MHU_CHAN_MAX;
	} else {
		dev_err(dev, "incorrect value of #mbox-cells in '%pOF'\n", np);
		return -EINVAL;
	}

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

	mhu->base = devm_ioremap_resource(dev, &adev->res);
	if (IS_ERR(mhu->base))
		return PTR_ERR(mhu->base);

	chans = devm_kcalloc(dev, max_chans, sizeof(*chans), GFP_KERNEL);
	if (!chans)
		return -ENOMEM;

	mhu->dev = dev;
	mhu->mbox.dev = dev;
	mhu->mbox.chans = chans;
	mhu->mbox.num_chans = max_chans;
	mhu->mbox.txdone_irq = false;
	mhu->mbox.txdone_poll = true;
	mhu->mbox.txpoll_period = 1;

	mhu->mbox.of_xlate = mhu_db_mbox_xlate;
	amba_set_drvdata(adev, mhu);

	mhu->mbox.ops = &mhu_db_ops;

	err = devm_mbox_controller_register(dev, &mhu->mbox);
	if (err) {
		dev_err(dev, "Failed to register mailboxes %d\n", err);
		return err;
	}

	for (i = 0; i < MHU_CHANS; i++) {
		int irq = mhu->mlink[i].irq = adev->irq[i];

		if (irq <= 0) {
			dev_dbg(dev, "No IRQ found for Channel %d\n", i);
			continue;
		}

		mhu->mlink[i].rx_reg = mhu->base + mhu_reg[i];
		mhu->mlink[i].tx_reg = mhu->mlink[i].rx_reg + TX_REG_OFFSET;

		err = devm_request_threaded_irq(dev, irq, NULL,
						mhu_db_mbox_rx_handler,
						IRQF_ONESHOT, "mhu_db_link", mhu);
		if (err) {
			dev_err(dev, "Can't claim IRQ %d\n", irq);
			mbox_controller_unregister(&mhu->mbox);
			return err;
		}
	}

	dev_info(dev, "ARM MHU Doorbell mailbox registered\n");
	return 0;
}

static struct amba_id mhu_ids[] = {
	{
		.id	= 0x1bb098,
		.mask	= 0xffffff,
	},
	{ 0, 0 },
};
MODULE_DEVICE_TABLE(amba, mhu_ids);

static struct amba_driver arm_mhu_db_driver = {
	.drv = {
		.name	= "mhu-doorbell",
	},
	.id_table	= mhu_ids,
	.probe		= mhu_db_probe,
};
module_amba_driver(arm_mhu_db_driver);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("ARM MHU Doorbell Driver");
MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");