/*
 *  H8/300 16bit Timer driver
 *
 *  Copyright 2015 Yoshinori Sato <ysato@users.sourcefoge.jp>
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/clocksource.h>
#include <linux/module.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/of.h>

#include <asm/segment.h>
#include <asm/irq.h>

#define TSTR	0
#define TSNC	1
#define TMDR	2
#define TOLR	3
#define TISRA	4
#define TISRB	5
#define TISRC	6

#define TCR	0
#define TIOR	1
#define TCNT	2
#define GRA	4
#define GRB	6

#define FLAG_REPROGRAM (1 << 0)
#define FLAG_SKIPEVENT (1 << 1)
#define FLAG_IRQCONTEXT (1 << 2)
#define FLAG_STARTED (1 << 3)

#define ONESHOT  0
#define PERIODIC 1

#define RELATIVE 0
#define ABSOLUTE 1

struct timer16_priv {
	struct platform_device *pdev;
	struct clocksource cs;
	struct irqaction irqaction;
	unsigned long total_cycles;
	unsigned long mapbase;
	unsigned long mapcommon;
	unsigned long flags;
	unsigned short gra;
	unsigned short cs_enabled;
	unsigned char enb;
	unsigned char imfa;
	unsigned char imiea;
	unsigned char ovf;
	raw_spinlock_t lock;
	struct clk *clk;
};

static unsigned long timer16_get_counter(struct timer16_priv *p)
{
	unsigned long v1, v2, v3;
	int o1, o2;

	o1 = ctrl_inb(p->mapcommon + TISRC) & p->ovf;

	/* Make sure the timer value is stable. Stolen from acpi_pm.c */
	do {
		o2 = o1;
		v1 = ctrl_inw(p->mapbase + TCNT);
		v2 = ctrl_inw(p->mapbase + TCNT);
		v3 = ctrl_inw(p->mapbase + TCNT);
		o1 = ctrl_inb(p->mapcommon + TISRC) & p->ovf;
	} while (unlikely((o1 != o2) || (v1 > v2 && v1 < v3)
			  || (v2 > v3 && v2 < v1) || (v3 > v1 && v3 < v2)));

	v2 |= 0x10000;
	return v2;
}


static irqreturn_t timer16_interrupt(int irq, void *dev_id)
{
	struct timer16_priv *p = (struct timer16_priv *)dev_id;

	ctrl_outb(ctrl_inb(p->mapcommon + TISRA) & ~p->imfa,
		  p->mapcommon + TISRA);
	p->total_cycles += 0x10000;

	return IRQ_HANDLED;
}

static inline struct timer16_priv *cs_to_priv(struct clocksource *cs)
{
	return container_of(cs, struct timer16_priv, cs);
}

static cycle_t timer16_clocksource_read(struct clocksource *cs)
{
	struct timer16_priv *p = cs_to_priv(cs);
	unsigned long flags, raw;
	unsigned long value;

	raw_spin_lock_irqsave(&p->lock, flags);
	value = p->total_cycles;
	raw = timer16_get_counter(p);
	raw_spin_unlock_irqrestore(&p->lock, flags);

	return value + raw;
}

static int timer16_enable(struct clocksource *cs)
{
	struct timer16_priv *p = cs_to_priv(cs);

	WARN_ON(p->cs_enabled);

	p->total_cycles = 0;
	ctrl_outw(0x0000, p->mapbase + TCNT);
	ctrl_outb(0x83, p->mapbase + TCR);
	ctrl_outb(ctrl_inb(p->mapcommon + TSTR) | p->enb,
		  p->mapcommon + TSTR);

	p->cs_enabled = true;
	return 0;
}

static void timer16_disable(struct clocksource *cs)
{
	struct timer16_priv *p = cs_to_priv(cs);

	WARN_ON(!p->cs_enabled);

	ctrl_outb(ctrl_inb(p->mapcommon + TSTR) & ~p->enb,
		  p->mapcommon + TSTR);

	p->cs_enabled = false;
}

#define REG_CH   0
#define REG_COMM 1

static int timer16_setup(struct timer16_priv *p, struct platform_device *pdev)
{
	struct resource *res[2];
	int ret, irq;
	unsigned int ch;

	memset(p, 0, sizeof(*p));
	p->pdev = pdev;

	res[REG_CH] = platform_get_resource(p->pdev,
					    IORESOURCE_MEM, REG_CH);
	res[REG_COMM] = platform_get_resource(p->pdev,
					      IORESOURCE_MEM, REG_COMM);
	if (!res[REG_CH] || !res[REG_COMM]) {
		dev_err(&p->pdev->dev, "failed to get I/O memory\n");
		return -ENXIO;
	}
	irq = platform_get_irq(p->pdev, 0);
	if (irq < 0) {
		dev_err(&p->pdev->dev, "failed to get irq\n");
		return irq;
	}

	p->clk = clk_get(&p->pdev->dev, "fck");
	if (IS_ERR(p->clk)) {
		dev_err(&p->pdev->dev, "can't get clk\n");
		return PTR_ERR(p->clk);
	}
	of_property_read_u32(p->pdev->dev.of_node, "renesas,channel", &ch);

	p->pdev = pdev;
	p->mapbase = res[REG_CH]->start;
	p->mapcommon = res[REG_COMM]->start;
	p->enb = 1 << ch;
	p->imfa = 1 << ch;
	p->imiea = 1 << (4 + ch);
	p->cs.name = pdev->name;
	p->cs.rating = 200;
	p->cs.read = timer16_clocksource_read;
	p->cs.enable = timer16_enable;
	p->cs.disable = timer16_disable;
	p->cs.mask = CLOCKSOURCE_MASK(sizeof(unsigned long) * 8);
	p->cs.flags = CLOCK_SOURCE_IS_CONTINUOUS;

	ret = request_irq(irq, timer16_interrupt,
			  IRQF_TIMER, pdev->name, p);
	if (ret < 0) {
		dev_err(&p->pdev->dev, "failed to request irq %d\n", irq);
		return ret;
	}

	clocksource_register_hz(&p->cs, clk_get_rate(p->clk) / 8);

	return 0;
}

static int timer16_probe(struct platform_device *pdev)
{
	struct timer16_priv *p = platform_get_drvdata(pdev);

	if (p) {
		dev_info(&pdev->dev, "kept as earlytimer\n");
		return 0;
	}

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

	return timer16_setup(p, pdev);
}

static int timer16_remove(struct platform_device *pdev)
{
	return -EBUSY;
}

static const struct of_device_id timer16_of_table[] = {
	{ .compatible = "renesas,16bit-timer" },
	{ }
};
static struct platform_driver timer16_driver = {
	.probe		= timer16_probe,
	.remove		= timer16_remove,
	.driver		= {
		.name	= "h8300h-16timer",
		.of_match_table = of_match_ptr(timer16_of_table),
	}
};

static int __init timer16_init(void)
{
	return platform_driver_register(&timer16_driver);
}

static void __exit timer16_exit(void)
{
	platform_driver_unregister(&timer16_driver);
}

subsys_initcall(timer16_init);
module_exit(timer16_exit);
MODULE_AUTHOR("Yoshinori Sato");
MODULE_DESCRIPTION("H8/300H 16bit Timer Driver");
MODULE_LICENSE("GPL v2");