/*
   *  linux/drivers/clocksource/zevio-timer.c
   *
   *  Copyright (C) 2013 Daniel Tang <tangrs@tangrs.id.au>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2, as
   * published by the Free Software Foundation.
   *
   */
  
  #include <linux/io.h>
  #include <linux/irq.h>
  #include <linux/of.h>
  #include <linux/of_address.h>
  #include <linux/of_irq.h>
  #include <linux/clk.h>
  #include <linux/clockchips.h>
  #include <linux/cpumask.h>
  #include <linux/interrupt.h>
  #include <linux/slab.h>
  
  #define IO_CURRENT_VAL	0x00
  #define IO_DIVIDER	0x04
  #define IO_CONTROL	0x08
  
  #define IO_TIMER1	0x00
  #define IO_TIMER2	0x0C
  
  #define IO_MATCH_BEGIN	0x18
  #define IO_MATCH(x)	(IO_MATCH_BEGIN + ((x) << 2))
  
  #define IO_INTR_STS	0x00
  #define IO_INTR_ACK	0x00
  #define IO_INTR_MSK	0x04
  
  #define CNTL_STOP_TIMER	(1 << 4)
  #define CNTL_RUN_TIMER	(0 << 4)
  
  #define CNTL_INC	(1 << 3)
  #define CNTL_DEC	(0 << 3)
  
  #define CNTL_TOZERO	0
  #define CNTL_MATCH(x)	((x) + 1)
  #define CNTL_FOREVER	7
  
  /* There are 6 match registers but we only use one. */
  #define TIMER_MATCH	0
  
  #define TIMER_INTR_MSK	(1 << (TIMER_MATCH))
  #define TIMER_INTR_ALL	0x3F
  
  struct zevio_timer {
  	void __iomem *base;
  	void __iomem *timer1, *timer2;
  	void __iomem *interrupt_regs;
  
  	struct clk *clk;
  	struct clock_event_device clkevt;
  	struct irqaction clkevt_irq;
  
  	char clocksource_name[64];
  	char clockevent_name[64];
  };
  
  static int zevio_timer_set_event(unsigned long delta,
  				 struct clock_event_device *dev)
  {
  	struct zevio_timer *timer = container_of(dev, struct zevio_timer,
  						 clkevt);
  
  	writel(delta, timer->timer1 + IO_CURRENT_VAL);
  	writel(CNTL_RUN_TIMER | CNTL_DEC | CNTL_MATCH(TIMER_MATCH),
  			timer->timer1 + IO_CONTROL);
  
  	return 0;
  }
  
  static int zevio_timer_shutdown(struct clock_event_device *dev)
  {
  	struct zevio_timer *timer = container_of(dev, struct zevio_timer,
  						 clkevt);
  
  	/* Disable timer interrupts */
  	writel(0, timer->interrupt_regs + IO_INTR_MSK);
  	writel(TIMER_INTR_ALL, timer->interrupt_regs + IO_INTR_ACK);
  	/* Stop timer */
  	writel(CNTL_STOP_TIMER, timer->timer1 + IO_CONTROL);
  	return 0;
  }
  
  static int zevio_timer_set_oneshot(struct clock_event_device *dev)
  {
  	struct zevio_timer *timer = container_of(dev, struct zevio_timer,
  						 clkevt);
  
  	/* Enable timer interrupts */
  	writel(TIMER_INTR_MSK, timer->interrupt_regs + IO_INTR_MSK);
  	writel(TIMER_INTR_ALL, timer->interrupt_regs + IO_INTR_ACK);
  	return 0;
  }
  
  static irqreturn_t zevio_timer_interrupt(int irq, void *dev_id)
  {
  	struct zevio_timer *timer = dev_id;
  	u32 intr;
  
  	intr = readl(timer->interrupt_regs + IO_INTR_ACK);
  	if (!(intr & TIMER_INTR_MSK))
  		return IRQ_NONE;
  
  	writel(TIMER_INTR_MSK, timer->interrupt_regs + IO_INTR_ACK);
  	writel(CNTL_STOP_TIMER, timer->timer1 + IO_CONTROL);
  
  	if (timer->clkevt.event_handler)
  		timer->clkevt.event_handler(&timer->clkevt);
  
  	return IRQ_HANDLED;
  }
  
  static int __init zevio_timer_add(struct device_node *node)
  {
  	struct zevio_timer *timer;
  	struct resource res;
  	int irqnr, ret;
  
  	timer = kzalloc(sizeof(*timer), GFP_KERNEL);
  	if (!timer)
  		return -ENOMEM;
  
  	timer->base = of_iomap(node, 0);
  	if (!timer->base) {
  		ret = -EINVAL;
  		goto error_free;
  	}
  	timer->timer1 = timer->base + IO_TIMER1;
  	timer->timer2 = timer->base + IO_TIMER2;
  
  	timer->clk = of_clk_get(node, 0);
  	if (IS_ERR(timer->clk)) {
  		ret = PTR_ERR(timer->clk);
  		pr_err("Timer clock not found! (error %d)
  ", ret);
  		goto error_unmap;
  	}
  
  	timer->interrupt_regs = of_iomap(node, 1);
  	irqnr = irq_of_parse_and_map(node, 0);
  
  	of_address_to_resource(node, 0, &res);
  	scnprintf(timer->clocksource_name, sizeof(timer->clocksource_name),
  			"%llx.%s_clocksource",
  			(unsigned long long)res.start, node->name);
  
  	scnprintf(timer->clockevent_name, sizeof(timer->clockevent_name),
  			"%llx.%s_clockevent",
  			(unsigned long long)res.start, node->name);
  
  	if (timer->interrupt_regs && irqnr) {
  		timer->clkevt.name		= timer->clockevent_name;
  		timer->clkevt.set_next_event	= zevio_timer_set_event;
  		timer->clkevt.set_state_shutdown = zevio_timer_shutdown;
  		timer->clkevt.set_state_oneshot = zevio_timer_set_oneshot;
  		timer->clkevt.tick_resume	= zevio_timer_set_oneshot;
  		timer->clkevt.rating		= 200;
  		timer->clkevt.cpumask		= cpu_all_mask;
  		timer->clkevt.features		= CLOCK_EVT_FEAT_ONESHOT;
  		timer->clkevt.irq		= irqnr;
  
  		writel(CNTL_STOP_TIMER, timer->timer1 + IO_CONTROL);
  		writel(0, timer->timer1 + IO_DIVIDER);
  
  		/* Start with timer interrupts disabled */
  		writel(0, timer->interrupt_regs + IO_INTR_MSK);
  		writel(TIMER_INTR_ALL, timer->interrupt_regs + IO_INTR_ACK);
  
  		/* Interrupt to occur when timer value matches 0 */
  		writel(0, timer->base + IO_MATCH(TIMER_MATCH));
  
  		timer->clkevt_irq.name		= timer->clockevent_name;
  		timer->clkevt_irq.handler	= zevio_timer_interrupt;
  		timer->clkevt_irq.dev_id	= timer;
  		timer->clkevt_irq.flags		= IRQF_TIMER | IRQF_IRQPOLL;
  
  		setup_irq(irqnr, &timer->clkevt_irq);
  
  		clockevents_config_and_register(&timer->clkevt,
  				clk_get_rate(timer->clk), 0x0001, 0xffff);
  		pr_info("Added %s as clockevent
  ", timer->clockevent_name);
  	}
  
  	writel(CNTL_STOP_TIMER, timer->timer2 + IO_CONTROL);
  	writel(0, timer->timer2 + IO_CURRENT_VAL);
  	writel(0, timer->timer2 + IO_DIVIDER);
  	writel(CNTL_RUN_TIMER | CNTL_FOREVER | CNTL_INC,
  			timer->timer2 + IO_CONTROL);
  
  	clocksource_mmio_init(timer->timer2 + IO_CURRENT_VAL,
  			timer->clocksource_name,
  			clk_get_rate(timer->clk),
  			200, 16,
  			clocksource_mmio_readw_up);
  
  	pr_info("Added %s as clocksource
  ", timer->clocksource_name);
  
  	return 0;
  error_unmap:
  	iounmap(timer->base);
  error_free:
  	kfree(timer);
  	return ret;
  }
  
  static void __init zevio_timer_init(struct device_node *node)
  {
  	BUG_ON(zevio_timer_add(node));
  }
  
  CLOCKSOURCE_OF_DECLARE(zevio_timer, "lsi,zevio-timer", zevio_timer_init);