/*
   * SuperH Timer Support - TMU
   *
   *  Copyright (C) 2009 Magnus Damm
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License
   *
   * This program is distributed in the hope that 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, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #include <linux/init.h>
  #include <linux/platform_device.h>
  #include <linux/spinlock.h>
  #include <linux/interrupt.h>
  #include <linux/ioport.h>
  #include <linux/delay.h>
  #include <linux/io.h>
  #include <linux/clk.h>
  #include <linux/irq.h>
  #include <linux/err.h>
  #include <linux/clocksource.h>
  #include <linux/clockchips.h>

  #include <linux/sh_timer.h>

  #include <linux/slab.h>

  #include <linux/module.h>

  
  struct sh_tmu_priv {
  	void __iomem *mapbase;
  	struct clk *clk;
  	struct irqaction irqaction;
  	struct platform_device *pdev;
  	unsigned long rate;
  	unsigned long periodic;
  	struct clock_event_device ced;
  	struct clocksource cs;
  };
  
  static DEFINE_SPINLOCK(sh_tmu_lock);
  
  #define TSTR -1 /* shared register */
  #define TCOR  0 /* channel register */
  #define TCNT 1 /* channel register */
  #define TCR 2 /* channel register */
  
  static inline unsigned long sh_tmu_read(struct sh_tmu_priv *p, int reg_nr)
  {

  	struct sh_timer_config *cfg = p->pdev->dev.platform_data;

  	void __iomem *base = p->mapbase;
  	unsigned long offs;
  
  	if (reg_nr == TSTR)
  		return ioread8(base - cfg->channel_offset);
  
  	offs = reg_nr << 2;
  
  	if (reg_nr == TCR)
  		return ioread16(base + offs);
  	else
  		return ioread32(base + offs);
  }
  
  static inline void sh_tmu_write(struct sh_tmu_priv *p, int reg_nr,
  				unsigned long value)
  {

  	struct sh_timer_config *cfg = p->pdev->dev.platform_data;

  	void __iomem *base = p->mapbase;
  	unsigned long offs;
  
  	if (reg_nr == TSTR) {
  		iowrite8(value, base - cfg->channel_offset);
  		return;
  	}
  
  	offs = reg_nr << 2;
  
  	if (reg_nr == TCR)
  		iowrite16(value, base + offs);
  	else
  		iowrite32(value, base + offs);
  }
  
  static void sh_tmu_start_stop_ch(struct sh_tmu_priv *p, int start)
  {

  	struct sh_timer_config *cfg = p->pdev->dev.platform_data;

  	unsigned long flags, value;
  
  	/* start stop register shared by multiple timer channels */
  	spin_lock_irqsave(&sh_tmu_lock, flags);
  	value = sh_tmu_read(p, TSTR);
  
  	if (start)
  		value |= 1 << cfg->timer_bit;
  	else
  		value &= ~(1 << cfg->timer_bit);
  
  	sh_tmu_write(p, TSTR, value);
  	spin_unlock_irqrestore(&sh_tmu_lock, flags);
  }
  
  static int sh_tmu_enable(struct sh_tmu_priv *p)
  {

  	int ret;

  	/* enable clock */

  	ret = clk_enable(p->clk);
  	if (ret) {

  		dev_err(&p->pdev->dev, "cannot enable clock
  ");

  		return ret;
  	}
  
  	/* make sure channel is disabled */
  	sh_tmu_start_stop_ch(p, 0);
  
  	/* maximum timeout */
  	sh_tmu_write(p, TCOR, 0xffffffff);
  	sh_tmu_write(p, TCNT, 0xffffffff);
  
  	/* configure channel to parent clock / 4, irq off */
  	p->rate = clk_get_rate(p->clk) / 4;
  	sh_tmu_write(p, TCR, 0x0000);
  
  	/* enable channel */
  	sh_tmu_start_stop_ch(p, 1);
  
  	return 0;
  }
  
  static void sh_tmu_disable(struct sh_tmu_priv *p)
  {
  	/* disable channel */
  	sh_tmu_start_stop_ch(p, 0);

  	/* disable interrupts in TMU block */
  	sh_tmu_write(p, TCR, 0x0000);

  	/* stop clock */

  	clk_disable(p->clk);
  }
  
  static void sh_tmu_set_next(struct sh_tmu_priv *p, unsigned long delta,
  			    int periodic)
  {
  	/* stop timer */
  	sh_tmu_start_stop_ch(p, 0);
  
  	/* acknowledge interrupt */
  	sh_tmu_read(p, TCR);
  
  	/* enable interrupt */
  	sh_tmu_write(p, TCR, 0x0020);
  
  	/* reload delta value in case of periodic timer */
  	if (periodic)
  		sh_tmu_write(p, TCOR, delta);
  	else

  		sh_tmu_write(p, TCOR, 0xffffffff);

  
  	sh_tmu_write(p, TCNT, delta);
  
  	/* start timer */
  	sh_tmu_start_stop_ch(p, 1);
  }
  
  static irqreturn_t sh_tmu_interrupt(int irq, void *dev_id)
  {
  	struct sh_tmu_priv *p = dev_id;
  
  	/* disable or acknowledge interrupt */
  	if (p->ced.mode == CLOCK_EVT_MODE_ONESHOT)
  		sh_tmu_write(p, TCR, 0x0000);
  	else
  		sh_tmu_write(p, TCR, 0x0020);
  
  	/* notify clockevent layer */
  	p->ced.event_handler(&p->ced);
  	return IRQ_HANDLED;
  }
  
  static struct sh_tmu_priv *cs_to_sh_tmu(struct clocksource *cs)
  {
  	return container_of(cs, struct sh_tmu_priv, cs);
  }
  
  static cycle_t sh_tmu_clocksource_read(struct clocksource *cs)
  {
  	struct sh_tmu_priv *p = cs_to_sh_tmu(cs);
  
  	return sh_tmu_read(p, TCNT) ^ 0xffffffff;
  }
  
  static int sh_tmu_clocksource_enable(struct clocksource *cs)
  {
  	struct sh_tmu_priv *p = cs_to_sh_tmu(cs);

  	int ret;

  	ret = sh_tmu_enable(p);
  	if (!ret)
  		__clocksource_updatefreq_hz(cs, p->rate);
  	return ret;

  }
  
  static void sh_tmu_clocksource_disable(struct clocksource *cs)
  {
  	sh_tmu_disable(cs_to_sh_tmu(cs));
  }
  
  static int sh_tmu_register_clocksource(struct sh_tmu_priv *p,
  				       char *name, unsigned long rating)
  {
  	struct clocksource *cs = &p->cs;
  
  	cs->name = name;
  	cs->rating = rating;
  	cs->read = sh_tmu_clocksource_read;
  	cs->enable = sh_tmu_clocksource_enable;
  	cs->disable = sh_tmu_clocksource_disable;
  	cs->mask = CLOCKSOURCE_MASK(32);
  	cs->flags = CLOCK_SOURCE_IS_CONTINUOUS;

  	dev_info(&p->pdev->dev, "used as clock source
  ");

  
  	/* Register with dummy 1 Hz value, gets updated in ->enable() */
  	clocksource_register_hz(cs, 1);

  	return 0;
  }
  
  static struct sh_tmu_priv *ced_to_sh_tmu(struct clock_event_device *ced)
  {
  	return container_of(ced, struct sh_tmu_priv, ced);
  }
  
  static void sh_tmu_clock_event_start(struct sh_tmu_priv *p, int periodic)
  {
  	struct clock_event_device *ced = &p->ced;
  
  	sh_tmu_enable(p);
  
  	/* TODO: calculate good shift from rate and counter bit width */
  
  	ced->shift = 32;
  	ced->mult = div_sc(p->rate, NSEC_PER_SEC, ced->shift);
  	ced->max_delta_ns = clockevent_delta2ns(0xffffffff, ced);
  	ced->min_delta_ns = 5000;
  
  	if (periodic) {
  		p->periodic = (p->rate + HZ/2) / HZ;
  		sh_tmu_set_next(p, p->periodic, 1);
  	}
  }
  
  static void sh_tmu_clock_event_mode(enum clock_event_mode mode,
  				    struct clock_event_device *ced)
  {
  	struct sh_tmu_priv *p = ced_to_sh_tmu(ced);
  	int disabled = 0;
  
  	/* deal with old setting first */
  	switch (ced->mode) {
  	case CLOCK_EVT_MODE_PERIODIC:
  	case CLOCK_EVT_MODE_ONESHOT:
  		sh_tmu_disable(p);
  		disabled = 1;
  		break;
  	default:
  		break;
  	}
  
  	switch (mode) {
  	case CLOCK_EVT_MODE_PERIODIC:

  		dev_info(&p->pdev->dev, "used for periodic clock events
  ");

  		sh_tmu_clock_event_start(p, 1);
  		break;
  	case CLOCK_EVT_MODE_ONESHOT:

  		dev_info(&p->pdev->dev, "used for oneshot clock events
  ");

  		sh_tmu_clock_event_start(p, 0);
  		break;
  	case CLOCK_EVT_MODE_UNUSED:
  		if (!disabled)
  			sh_tmu_disable(p);
  		break;
  	case CLOCK_EVT_MODE_SHUTDOWN:
  	default:
  		break;
  	}
  }
  
  static int sh_tmu_clock_event_next(unsigned long delta,
  				   struct clock_event_device *ced)
  {
  	struct sh_tmu_priv *p = ced_to_sh_tmu(ced);
  
  	BUG_ON(ced->mode != CLOCK_EVT_MODE_ONESHOT);
  
  	/* program new delta value */
  	sh_tmu_set_next(p, delta, 0);
  	return 0;
  }
  
  static void sh_tmu_register_clockevent(struct sh_tmu_priv *p,
  				       char *name, unsigned long rating)
  {
  	struct clock_event_device *ced = &p->ced;
  	int ret;
  
  	memset(ced, 0, sizeof(*ced));
  
  	ced->name = name;
  	ced->features = CLOCK_EVT_FEAT_PERIODIC;
  	ced->features |= CLOCK_EVT_FEAT_ONESHOT;
  	ced->rating = rating;
  	ced->cpumask = cpumask_of(0);
  	ced->set_next_event = sh_tmu_clock_event_next;
  	ced->set_mode = sh_tmu_clock_event_mode;

  	dev_info(&p->pdev->dev, "used for clock events
  ");

  	clockevents_register_device(ced);

  	ret = setup_irq(p->irqaction.irq, &p->irqaction);
  	if (ret) {

  		dev_err(&p->pdev->dev, "failed to request irq %d
  ",
  			p->irqaction.irq);

  		return;
  	}

  }
  
  static int sh_tmu_register(struct sh_tmu_priv *p, char *name,
  		    unsigned long clockevent_rating,
  		    unsigned long clocksource_rating)
  {
  	if (clockevent_rating)
  		sh_tmu_register_clockevent(p, name, clockevent_rating);
  	else if (clocksource_rating)
  		sh_tmu_register_clocksource(p, name, clocksource_rating);
  
  	return 0;
  }
  
  static int sh_tmu_setup(struct sh_tmu_priv *p, struct platform_device *pdev)
  {

  	struct sh_timer_config *cfg = pdev->dev.platform_data;

  	struct resource *res;
  	int irq, ret;
  	ret = -ENXIO;
  
  	memset(p, 0, sizeof(*p));
  	p->pdev = pdev;
  
  	if (!cfg) {
  		dev_err(&p->pdev->dev, "missing platform data
  ");
  		goto err0;
  	}
  
  	platform_set_drvdata(pdev, p);
  
  	res = platform_get_resource(p->pdev, IORESOURCE_MEM, 0);
  	if (!res) {
  		dev_err(&p->pdev->dev, "failed to get I/O memory
  ");
  		goto err0;
  	}
  
  	irq = platform_get_irq(p->pdev, 0);
  	if (irq < 0) {
  		dev_err(&p->pdev->dev, "failed to get irq
  ");
  		goto err0;
  	}
  
  	/* map memory, let mapbase point to our channel */
  	p->mapbase = ioremap_nocache(res->start, resource_size(res));
  	if (p->mapbase == NULL) {

  		dev_err(&p->pdev->dev, "failed to remap I/O memory
  ");

  		goto err0;
  	}
  
  	/* setup data for setup_irq() (too early for request_irq()) */

  	p->irqaction.name = dev_name(&p->pdev->dev);

  	p->irqaction.handler = sh_tmu_interrupt;
  	p->irqaction.dev_id = p;
  	p->irqaction.irq = irq;

  	p->irqaction.flags = IRQF_DISABLED | IRQF_TIMER | \
  			     IRQF_IRQPOLL  | IRQF_NOBALANCING;

  
  	/* get hold of clock */

  	p->clk = clk_get(&p->pdev->dev, "tmu_fck");

  	if (IS_ERR(p->clk)) {

  		dev_err(&p->pdev->dev, "cannot get clock
  ");
  		ret = PTR_ERR(p->clk);
  		goto err1;

  	}

  	return sh_tmu_register(p, (char *)dev_name(&p->pdev->dev),

  			       cfg->clockevent_rating,
  			       cfg->clocksource_rating);
   err1:
  	iounmap(p->mapbase);
   err0:
  	return ret;
  }
  
  static int __devinit sh_tmu_probe(struct platform_device *pdev)
  {
  	struct sh_tmu_priv *p = platform_get_drvdata(pdev);

  	int ret;
  
  	if (p) {

  		dev_info(&pdev->dev, "kept as earlytimer
  ");

  		return 0;
  	}
  
  	p = kmalloc(sizeof(*p), GFP_KERNEL);
  	if (p == NULL) {
  		dev_err(&pdev->dev, "failed to allocate driver data
  ");
  		return -ENOMEM;
  	}
  
  	ret = sh_tmu_setup(p, pdev);
  	if (ret) {
  		kfree(p);
  		platform_set_drvdata(pdev, NULL);
  	}
  	return ret;
  }
  
  static int __devexit sh_tmu_remove(struct platform_device *pdev)
  {
  	return -EBUSY; /* cannot unregister clockevent and clocksource */
  }
  
  static struct platform_driver sh_tmu_device_driver = {
  	.probe		= sh_tmu_probe,
  	.remove		= __devexit_p(sh_tmu_remove),
  	.driver		= {
  		.name	= "sh_tmu",
  	}
  };
  
  static int __init sh_tmu_init(void)
  {
  	return platform_driver_register(&sh_tmu_device_driver);
  }
  
  static void __exit sh_tmu_exit(void)
  {
  	platform_driver_unregister(&sh_tmu_device_driver);
  }
  
  early_platform_init("earlytimer", &sh_tmu_device_driver);
  module_init(sh_tmu_init);
  module_exit(sh_tmu_exit);
  
  MODULE_AUTHOR("Magnus Damm");
  MODULE_DESCRIPTION("SuperH TMU Timer Driver");
  MODULE_LICENSE("GPL v2");