/*
   * Copyright (C) 2008 STMicroelectronics
   * Copyright (C) 2010 Alessandro Rubini
   * Copyright (C) 2010 Linus Walleij for ST-Ericsson
   *
   * 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/init.h>
  #include <linux/interrupt.h>
  #include <linux/irq.h>
  #include <linux/io.h>
  #include <linux/clockchips.h>
  #include <linux/clocksource.h>
  #include <linux/of_address.h>
  #include <linux/of_irq.h>
  #include <linux/of_platform.h>
  #include <linux/clk.h>
  #include <linux/jiffies.h>
  #include <linux/delay.h>
  #include <linux/err.h>
  #include <linux/sched_clock.h>
  #include <asm/mach/time.h>
  
  /*
   * The MTU device hosts four different counters, with 4 set of
   * registers. These are register names.
   */
  
  #define MTU_IMSC	0x00	/* Interrupt mask set/clear */
  #define MTU_RIS		0x04	/* Raw interrupt status */
  #define MTU_MIS		0x08	/* Masked interrupt status */
  #define MTU_ICR		0x0C	/* Interrupt clear register */
  
  /* per-timer registers take 0..3 as argument */
  #define MTU_LR(x)	(0x10 + 0x10 * (x) + 0x00)	/* Load value */
  #define MTU_VAL(x)	(0x10 + 0x10 * (x) + 0x04)	/* Current value */
  #define MTU_CR(x)	(0x10 + 0x10 * (x) + 0x08)	/* Control reg */
  #define MTU_BGLR(x)	(0x10 + 0x10 * (x) + 0x0c)	/* At next overflow */
  
  /* bits for the control register */
  #define MTU_CRn_ENA		0x80
  #define MTU_CRn_PERIODIC	0x40	/* if 0 = free-running */
  #define MTU_CRn_PRESCALE_MASK	0x0c
  #define MTU_CRn_PRESCALE_1		0x00
  #define MTU_CRn_PRESCALE_16		0x04
  #define MTU_CRn_PRESCALE_256		0x08
  #define MTU_CRn_32BITS		0x02
  #define MTU_CRn_ONESHOT		0x01	/* if 0 = wraps reloading from BGLR*/
  
  /* Other registers are usual amba/primecell registers, currently not used */
  #define MTU_ITCR	0xff0
  #define MTU_ITOP	0xff4
  
  #define MTU_PERIPH_ID0	0xfe0
  #define MTU_PERIPH_ID1	0xfe4
  #define MTU_PERIPH_ID2	0xfe8
  #define MTU_PERIPH_ID3	0xfeC
  
  #define MTU_PCELL0	0xff0
  #define MTU_PCELL1	0xff4
  #define MTU_PCELL2	0xff8
  #define MTU_PCELL3	0xffC
  
  static void __iomem *mtu_base;
  static bool clkevt_periodic;
  static u32 clk_prescale;
  static u32 nmdk_cycle;		/* write-once */
  static struct delay_timer mtu_delay_timer;
  
  #ifdef CONFIG_CLKSRC_NOMADIK_MTU_SCHED_CLOCK
  /*
   * Override the global weak sched_clock symbol with this
   * local implementation which uses the clocksource to get some
   * better resolution when scheduling the kernel.
   */
  static u64 notrace nomadik_read_sched_clock(void)
  {
  	if (unlikely(!mtu_base))
  		return 0;
  
  	return -readl(mtu_base + MTU_VAL(0));
  }
  #endif
  
  static unsigned long nmdk_timer_read_current_timer(void)
  {
  	return ~readl_relaxed(mtu_base + MTU_VAL(0));
  }
  
  /* Clockevent device: use one-shot mode */
  static int nmdk_clkevt_next(unsigned long evt, struct clock_event_device *ev)
  {
  	writel(1 << 1, mtu_base + MTU_IMSC);
  	writel(evt, mtu_base + MTU_LR(1));
  	/* Load highest value, enable device, enable interrupts */
  	writel(MTU_CRn_ONESHOT | clk_prescale |
  	       MTU_CRn_32BITS | MTU_CRn_ENA,
  	       mtu_base + MTU_CR(1));
  
  	return 0;
  }
  
  static void nmdk_clkevt_reset(void)
  {
  	if (clkevt_periodic) {
  		/* Timer: configure load and background-load, and fire it up */
  		writel(nmdk_cycle, mtu_base + MTU_LR(1));
  		writel(nmdk_cycle, mtu_base + MTU_BGLR(1));
  
  		writel(MTU_CRn_PERIODIC | clk_prescale |
  		       MTU_CRn_32BITS | MTU_CRn_ENA,
  		       mtu_base + MTU_CR(1));
  		writel(1 << 1, mtu_base + MTU_IMSC);
  	} else {
  		/* Generate an interrupt to start the clockevent again */
  		(void) nmdk_clkevt_next(nmdk_cycle, NULL);
  	}
  }
  
  static void nmdk_clkevt_mode(enum clock_event_mode mode,
  			     struct clock_event_device *dev)
  {
  	switch (mode) {
  	case CLOCK_EVT_MODE_PERIODIC:
  		clkevt_periodic = true;
  		nmdk_clkevt_reset();
  		break;
  	case CLOCK_EVT_MODE_ONESHOT:
  		clkevt_periodic = false;
  		break;
  	case CLOCK_EVT_MODE_SHUTDOWN:
  	case CLOCK_EVT_MODE_UNUSED:
  		writel(0, mtu_base + MTU_IMSC);
  		/* disable timer */
  		writel(0, mtu_base + MTU_CR(1));
  		/* load some high default value */
  		writel(0xffffffff, mtu_base + MTU_LR(1));
  		break;
  	case CLOCK_EVT_MODE_RESUME:
  		break;
  	}
  }
  
  static void nmdk_clksrc_reset(void)
  {
  	/* Disable */
  	writel(0, mtu_base + MTU_CR(0));
  
  	/* ClockSource: configure load and background-load, and fire it up */
  	writel(nmdk_cycle, mtu_base + MTU_LR(0));
  	writel(nmdk_cycle, mtu_base + MTU_BGLR(0));
  
  	writel(clk_prescale | MTU_CRn_32BITS | MTU_CRn_ENA,
  	       mtu_base + MTU_CR(0));
  }
  
  static void nmdk_clkevt_resume(struct clock_event_device *cedev)
  {
  	nmdk_clkevt_reset();
  	nmdk_clksrc_reset();
  }
  
  static struct clock_event_device nmdk_clkevt = {
  	.name		= "mtu_1",
  	.features	= CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC |
  	                  CLOCK_EVT_FEAT_DYNIRQ,
  	.rating		= 200,
  	.set_mode	= nmdk_clkevt_mode,
  	.set_next_event	= nmdk_clkevt_next,
  	.resume		= nmdk_clkevt_resume,
  };
  
  /*
   * IRQ Handler for timer 1 of the MTU block.
   */
  static irqreturn_t nmdk_timer_interrupt(int irq, void *dev_id)
  {
  	struct clock_event_device *evdev = dev_id;
  
  	writel(1 << 1, mtu_base + MTU_ICR); /* Interrupt clear reg */
  	evdev->event_handler(evdev);
  	return IRQ_HANDLED;
  }
  
  static struct irqaction nmdk_timer_irq = {
  	.name		= "Nomadik Timer Tick",
  	.flags		= IRQF_TIMER,
  	.handler	= nmdk_timer_interrupt,
  	.dev_id		= &nmdk_clkevt,
  };
  
  static void __init nmdk_timer_init(void __iomem *base, int irq,
  				   struct clk *pclk, struct clk *clk)
  {
  	unsigned long rate;
  
  	mtu_base = base;
  
  	BUG_ON(clk_prepare_enable(pclk));
  	BUG_ON(clk_prepare_enable(clk));
  
  	/*
  	 * Tick rate is 2.4MHz for Nomadik and 2.4Mhz, 100MHz or 133 MHz
  	 * for ux500.
  	 * Use a divide-by-16 counter if the tick rate is more than 32MHz.
  	 * At 32 MHz, the timer (with 32 bit counter) can be programmed
  	 * to wake-up at a max 127s a head in time. Dividing a 2.4 MHz timer
  	 * with 16 gives too low timer resolution.
  	 */
  	rate = clk_get_rate(clk);
  	if (rate > 32000000) {
  		rate /= 16;
  		clk_prescale = MTU_CRn_PRESCALE_16;
  	} else {
  		clk_prescale = MTU_CRn_PRESCALE_1;
  	}
  
  	/* Cycles for periodic mode */
  	nmdk_cycle = DIV_ROUND_CLOSEST(rate, HZ);
  
  
  	/* Timer 0 is the free running clocksource */
  	nmdk_clksrc_reset();
  
  	if (clocksource_mmio_init(mtu_base + MTU_VAL(0), "mtu_0",
  			rate, 200, 32, clocksource_mmio_readl_down))
  		pr_err("timer: failed to initialize clock source %s
  ",
  		       "mtu_0");
  
  #ifdef CONFIG_CLKSRC_NOMADIK_MTU_SCHED_CLOCK
  	sched_clock_register(nomadik_read_sched_clock, 32, rate);
  #endif
  
  	/* Timer 1 is used for events, register irq and clockevents */
  	setup_irq(irq, &nmdk_timer_irq);
  	nmdk_clkevt.cpumask = cpumask_of(0);
  	nmdk_clkevt.irq = irq;
  	clockevents_config_and_register(&nmdk_clkevt, rate, 2, 0xffffffffU);
  
  	mtu_delay_timer.read_current_timer = &nmdk_timer_read_current_timer;
  	mtu_delay_timer.freq = rate;
  	register_current_timer_delay(&mtu_delay_timer);
  }
  
  static void __init nmdk_timer_of_init(struct device_node *node)
  {
  	struct clk *pclk;
  	struct clk *clk;
  	void __iomem *base;
  	int irq;
  
  	base = of_iomap(node, 0);
  	if (!base)
  		panic("Can't remap registers");
  
  	pclk = of_clk_get_by_name(node, "apb_pclk");
  	if (IS_ERR(pclk))
  		panic("could not get apb_pclk");
  
  	clk = of_clk_get_by_name(node, "timclk");
  	if (IS_ERR(clk))
  		panic("could not get timclk");
  
  	irq = irq_of_parse_and_map(node, 0);
  	if (irq <= 0)
  		panic("Can't parse IRQ");
  
  	nmdk_timer_init(base, irq, pclk, clk);
  }
  CLOCKSOURCE_OF_DECLARE(nomadik_mtu, "st,nomadik-mtu",
  		       nmdk_timer_of_init);