/*
 * Copyright Altera Corporation (C) 2013-2014. All rights reserved
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/device.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>
#include <linux/platform_device.h>

#define DRIVER_NAME	"altera-mailbox"

#define MAILBOX_CMD_REG			0x00
#define MAILBOX_PTR_REG			0x04
#define MAILBOX_STS_REG			0x08
#define MAILBOX_INTMASK_REG		0x0C

#define INT_PENDING_MSK			0x1
#define INT_SPACE_MSK			0x2

#define STS_PENDING_MSK			0x1
#define STS_FULL_MSK			0x2
#define STS_FULL_OFT			0x1

#define MBOX_PENDING(status)	(((status) & STS_PENDING_MSK))
#define MBOX_FULL(status)	(((status) & STS_FULL_MSK) >> STS_FULL_OFT)

enum altera_mbox_msg {
	MBOX_CMD = 0,
	MBOX_PTR,
};

#define MBOX_POLLING_MS		5	/* polling interval 5ms */

struct altera_mbox {
	bool is_sender;		/* 1-sender, 0-receiver */
	bool intr_mode;
	int irq;
	void __iomem *mbox_base;
	struct device *dev;
	struct mbox_controller controller;

	/* If the controller supports only RX polling mode */
	struct timer_list rxpoll_timer;
};

static struct altera_mbox *mbox_chan_to_altera_mbox(struct mbox_chan *chan)
{
	if (!chan || !chan->con_priv)
		return NULL;

	return (struct altera_mbox *)chan->con_priv;
}

static inline int altera_mbox_full(struct altera_mbox *mbox)
{
	u32 status;

	status = readl_relaxed(mbox->mbox_base + MAILBOX_STS_REG);
	return MBOX_FULL(status);
}

static inline int altera_mbox_pending(struct altera_mbox *mbox)
{
	u32 status;

	status = readl_relaxed(mbox->mbox_base + MAILBOX_STS_REG);
	return MBOX_PENDING(status);
}

static void altera_mbox_rx_intmask(struct altera_mbox *mbox, bool enable)
{
	u32 mask;

	mask = readl_relaxed(mbox->mbox_base + MAILBOX_INTMASK_REG);
	if (enable)
		mask |= INT_PENDING_MSK;
	else
		mask &= ~INT_PENDING_MSK;
	writel_relaxed(mask, mbox->mbox_base + MAILBOX_INTMASK_REG);
}

static void altera_mbox_tx_intmask(struct altera_mbox *mbox, bool enable)
{
	u32 mask;

	mask = readl_relaxed(mbox->mbox_base + MAILBOX_INTMASK_REG);
	if (enable)
		mask |= INT_SPACE_MSK;
	else
		mask &= ~INT_SPACE_MSK;
	writel_relaxed(mask, mbox->mbox_base + MAILBOX_INTMASK_REG);
}

static bool altera_mbox_is_sender(struct altera_mbox *mbox)
{
	u32 reg;
	/* Write a magic number to PTR register and read back this register.
	 * This register is read-write if it is a sender.
	 */
	#define MBOX_MAGIC	0xA5A5AA55
	writel_relaxed(MBOX_MAGIC, mbox->mbox_base + MAILBOX_PTR_REG);
	reg = readl_relaxed(mbox->mbox_base + MAILBOX_PTR_REG);
	if (reg == MBOX_MAGIC) {
		/* Clear to 0 */
		writel_relaxed(0, mbox->mbox_base + MAILBOX_PTR_REG);
		return true;
	}
	return false;
}

static void altera_mbox_rx_data(struct mbox_chan *chan)
{
	struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);
	u32 data[2];

	if (altera_mbox_pending(mbox)) {
		data[MBOX_PTR] =
			readl_relaxed(mbox->mbox_base + MAILBOX_PTR_REG);
		data[MBOX_CMD] =
			readl_relaxed(mbox->mbox_base + MAILBOX_CMD_REG);
		mbox_chan_received_data(chan, (void *)data);
	}
}

static void altera_mbox_poll_rx(unsigned long data)
{
	struct mbox_chan *chan = (struct mbox_chan *)data;
	struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);

	altera_mbox_rx_data(chan);

	mod_timer(&mbox->rxpoll_timer,
		  jiffies + msecs_to_jiffies(MBOX_POLLING_MS));
}

static irqreturn_t altera_mbox_tx_interrupt(int irq, void *p)
{
	struct mbox_chan *chan = (struct mbox_chan *)p;
	struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);

	altera_mbox_tx_intmask(mbox, false);
	mbox_chan_txdone(chan, 0);

	return IRQ_HANDLED;
}

static irqreturn_t altera_mbox_rx_interrupt(int irq, void *p)
{
	struct mbox_chan *chan = (struct mbox_chan *)p;

	altera_mbox_rx_data(chan);
	return IRQ_HANDLED;
}

static int altera_mbox_startup_sender(struct mbox_chan *chan)
{
	int ret;
	struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);

	if (mbox->intr_mode) {
		ret = request_irq(mbox->irq, altera_mbox_tx_interrupt, 0,
				  DRIVER_NAME, chan);
		if (unlikely(ret)) {
			dev_err(mbox->dev,
				"failed to register mailbox interrupt:%d\n",
				ret);
			return ret;
		}
	}

	return 0;
}

static int altera_mbox_startup_receiver(struct mbox_chan *chan)
{
	int ret;
	struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);

	if (mbox->intr_mode) {
		ret = request_irq(mbox->irq, altera_mbox_rx_interrupt, 0,
				  DRIVER_NAME, chan);
		if (unlikely(ret)) {
			mbox->intr_mode = false;
			goto polling; /* use polling if failed */
		}

		altera_mbox_rx_intmask(mbox, true);
		return 0;
	}

polling:
	/* Setup polling timer */
	setup_timer(&mbox->rxpoll_timer, altera_mbox_poll_rx,
		    (unsigned long)chan);
	mod_timer(&mbox->rxpoll_timer,
		  jiffies + msecs_to_jiffies(MBOX_POLLING_MS));

	return 0;
}

static int altera_mbox_send_data(struct mbox_chan *chan, void *data)
{
	struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);
	u32 *udata = (u32 *)data;

	if (!mbox || !data)
		return -EINVAL;
	if (!mbox->is_sender) {
		dev_warn(mbox->dev,
			 "failed to send. This is receiver mailbox.\n");
		return -EINVAL;
	}

	if (altera_mbox_full(mbox))
		return -EBUSY;

	/* Enable interrupt before send */
	if (mbox->intr_mode)
		altera_mbox_tx_intmask(mbox, true);

	/* Pointer register must write before command register */
	writel_relaxed(udata[MBOX_PTR], mbox->mbox_base + MAILBOX_PTR_REG);
	writel_relaxed(udata[MBOX_CMD], mbox->mbox_base + MAILBOX_CMD_REG);

	return 0;
}

static bool altera_mbox_last_tx_done(struct mbox_chan *chan)
{
	struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);

	/* Return false if mailbox is full */
	return altera_mbox_full(mbox) ? false : true;
}

static bool altera_mbox_peek_data(struct mbox_chan *chan)
{
	struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);

	return altera_mbox_pending(mbox) ? true : false;
}

static int altera_mbox_startup(struct mbox_chan *chan)
{
	struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);
	int ret = 0;

	if (!mbox)
		return -EINVAL;

	if (mbox->is_sender)
		ret = altera_mbox_startup_sender(chan);
	else
		ret = altera_mbox_startup_receiver(chan);

	return ret;
}

static void altera_mbox_shutdown(struct mbox_chan *chan)
{
	struct altera_mbox *mbox = mbox_chan_to_altera_mbox(chan);

	if (mbox->intr_mode) {
		/* Unmask all interrupt masks */
		writel_relaxed(~0, mbox->mbox_base + MAILBOX_INTMASK_REG);
		free_irq(mbox->irq, chan);
	} else if (!mbox->is_sender) {
		del_timer_sync(&mbox->rxpoll_timer);
	}
}

static const struct mbox_chan_ops altera_mbox_ops = {
	.send_data = altera_mbox_send_data,
	.startup = altera_mbox_startup,
	.shutdown = altera_mbox_shutdown,
	.last_tx_done = altera_mbox_last_tx_done,
	.peek_data = altera_mbox_peek_data,
};

static int altera_mbox_probe(struct platform_device *pdev)
{
	struct altera_mbox *mbox;
	struct resource	*regs;
	struct mbox_chan *chans;
	int ret;

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

	/* Allocated one channel */
	chans = devm_kzalloc(&pdev->dev, sizeof(*chans), GFP_KERNEL);
	if (!chans)
		return -ENOMEM;

	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);

	mbox->mbox_base = devm_ioremap_resource(&pdev->dev, regs);
	if (IS_ERR(mbox->mbox_base))
		return PTR_ERR(mbox->mbox_base);

	/* Check is it a sender or receiver? */
	mbox->is_sender = altera_mbox_is_sender(mbox);

	mbox->irq = platform_get_irq(pdev, 0);
	if (mbox->irq >= 0)
		mbox->intr_mode = true;

	mbox->dev = &pdev->dev;

	/* Hardware supports only one channel. */
	chans[0].con_priv = mbox;
	mbox->controller.dev = mbox->dev;
	mbox->controller.num_chans = 1;
	mbox->controller.chans = chans;
	mbox->controller.ops = &altera_mbox_ops;

	if (mbox->is_sender) {
		if (mbox->intr_mode) {
			mbox->controller.txdone_irq = true;
		} else {
			mbox->controller.txdone_poll = true;
			mbox->controller.txpoll_period = MBOX_POLLING_MS;
		}
	}

	ret = mbox_controller_register(&mbox->controller);
	if (ret) {
		dev_err(&pdev->dev, "Register mailbox failed\n");
		goto err;
	}

	platform_set_drvdata(pdev, mbox);
err:
	return ret;
}

static int altera_mbox_remove(struct platform_device *pdev)
{
	struct altera_mbox *mbox = platform_get_drvdata(pdev);

	if (!mbox)
		return -EINVAL;

	mbox_controller_unregister(&mbox->controller);

	return 0;
}

static const struct of_device_id altera_mbox_match[] = {
	{ .compatible = "altr,mailbox-1.0" },
	{ /* Sentinel */ }
};

MODULE_DEVICE_TABLE(of, altera_mbox_match);

static struct platform_driver altera_mbox_driver = {
	.probe	= altera_mbox_probe,
	.remove	= altera_mbox_remove,
	.driver	= {
		.name	= DRIVER_NAME,
		.of_match_table	= altera_mbox_match,
	},
};

module_platform_driver(altera_mbox_driver);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Altera mailbox specific functions");
MODULE_AUTHOR("Ley Foon Tan <lftan@altera.com>");
MODULE_ALIAS("platform:altera-mailbox");