// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 2023 Raspberry Pi Ltd.
 *
 * Parts of this driver are based on:
 *  - bcm2835-mailbox.c
 *    Copyright (C) 2010,2015 Broadcom
 *    Copyright (C) 2013-2014 Lubomir Rintel
 *    Copyright (C) 2013 Craig McGeachie
 */

#include <linux/compat.h>
#include <linux/device.h>
#include <linux/dma-mapping.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/mailbox_controller.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/platform_device.h>

/*
 * RP1's PROC_EVENTS register can generate interrupts on the M3 cores (when
 * enabled). The 32-bit register is treated as 32 events, all of which share a
 * common interrupt. HOST_EVENTS is the same in the reverse direction.
 */
#define SYSCFG_PROC_EVENTS		0x00000008
#define SYSCFG_HOST_EVENTS		0x0000000c
#define SYSCFG_HOST_EVENT_IRQ_EN	0x00000010
#define SYSCFG_HOST_EVENT_IRQ		0x00000014

#define HW_SET_BITS			0x00002000
#define HW_CLR_BITS			0x00003000

#define MAX_CHANS	4 /* 32 is the hardware limit */

struct rp1_mbox {
	void __iomem *regs;
	unsigned int irq;
	struct mbox_controller controller;
};

static struct rp1_mbox *rp1_chan_mbox(struct mbox_chan *chan)
{
	return container_of(chan->mbox, struct rp1_mbox, controller);
}

static unsigned int rp1_chan_event(struct mbox_chan *chan)
{
	return (unsigned int)(uintptr_t)chan->con_priv;
}

static irqreturn_t rp1_mbox_irq(int irq, void *dev_id)
{
	struct rp1_mbox *mbox = dev_id;
	struct mbox_chan *chan;
	unsigned int doorbell;
	unsigned int evs;

	evs = readl(mbox->regs + SYSCFG_HOST_EVENT_IRQ);
	writel(evs, mbox->regs + SYSCFG_HOST_EVENTS + HW_CLR_BITS);

	while (evs) {
		doorbell = __ffs(evs);
		chan = &mbox->controller.chans[doorbell];
		mbox_chan_received_data(chan, NULL);
		evs &= ~(1 << doorbell);
	}
	return IRQ_HANDLED;
}

static int rp1_send_data(struct mbox_chan *chan, void *data)
{
	struct rp1_mbox *mbox = rp1_chan_mbox(chan);
	unsigned int event = rp1_chan_event(chan);

	writel(event, mbox->regs + SYSCFG_PROC_EVENTS + HW_SET_BITS);

	return 0;
}

static int rp1_startup(struct mbox_chan *chan)
{
	struct rp1_mbox *mbox = rp1_chan_mbox(chan);
	unsigned int event = rp1_chan_event(chan);

	writel(event, mbox->regs + SYSCFG_HOST_EVENT_IRQ_EN + HW_SET_BITS);

	return 0;
}

static void rp1_shutdown(struct mbox_chan *chan)
{
	struct rp1_mbox *mbox = rp1_chan_mbox(chan);
	unsigned int event = rp1_chan_event(chan);

	writel(event, mbox->regs + SYSCFG_HOST_EVENT_IRQ_EN + HW_CLR_BITS);
}

static bool rp1_last_tx_done(struct mbox_chan *chan)
{
	struct rp1_mbox *mbox = rp1_chan_mbox(chan);
	unsigned int event = rp1_chan_event(chan);
	unsigned int evs;

	evs = readl(mbox->regs + SYSCFG_HOST_EVENT_IRQ);

	return !(evs & event);
}

static const struct mbox_chan_ops rp1_mbox_chan_ops = {
	.send_data	= rp1_send_data,
	.startup	= rp1_startup,
	.shutdown	= rp1_shutdown,
	.last_tx_done	= rp1_last_tx_done
};

static struct mbox_chan *rp1_mbox_xlate(struct mbox_controller *mbox,
					const struct of_phandle_args *spec)
{
	struct mbox_chan *chan;
	unsigned int doorbell;

	if (spec->args_count != 1)
		return ERR_PTR(-EINVAL);

	doorbell = spec->args[0];
	if (doorbell >= MAX_CHANS)
		return ERR_PTR(-EINVAL);

	chan = &mbox->chans[doorbell];
	if (chan->con_priv)
		return ERR_PTR(-EBUSY);

	chan->con_priv = (void *)(uintptr_t)(1 << doorbell);

	return chan;
}

static int rp1_mbox_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct mbox_chan *chans;
	struct rp1_mbox *mbox;
	int ret = 0;

	mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
	if (mbox == NULL)
		return -ENOMEM;

	ret = devm_request_irq(dev, platform_get_irq(pdev, 0),
			       rp1_mbox_irq, 0, dev_name(dev), mbox);
	if (ret) {
		dev_err(dev, "Failed to register a mailbox IRQ handler: %d\n",
			ret);
		return -ENODEV;
	}

	mbox->regs = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(mbox->regs)) {
		ret = PTR_ERR(mbox->regs);
		return ret;
	}

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

	mbox->controller.txdone_poll = true;
	mbox->controller.txpoll_period = 5;
	mbox->controller.ops = &rp1_mbox_chan_ops;
	mbox->controller.of_xlate = &rp1_mbox_xlate;
	mbox->controller.dev = dev;
	mbox->controller.num_chans = MAX_CHANS;
	mbox->controller.chans = chans;

	ret = devm_mbox_controller_register(dev, &mbox->controller);
	if (ret)
		return ret;

	platform_set_drvdata(pdev, mbox);

	return 0;
}

static const struct of_device_id rp1_mbox_of_match[] = {
	{ .compatible = "raspberrypi,rp1-mbox", },
	{},
};
MODULE_DEVICE_TABLE(of, rp1_mbox_of_match);

static struct platform_driver rp1_mbox_driver = {
	.driver = {
		.name = "rp1-mbox",
		.of_match_table = rp1_mbox_of_match,
	},
	.probe = rp1_mbox_probe,
};

module_platform_driver(rp1_mbox_driver);

MODULE_AUTHOR("Phil Elwell <phil@raspberrypi.com>");
MODULE_DESCRIPTION("RP1 mailbox IPC driver");
MODULE_LICENSE("GPL v2");