/*
   * System timer for CSR SiRFprimaII
   *
   * Copyright (c) 2011 Cambridge Silicon Radio Limited, a CSR plc group company.
   *
   * Licensed under GPLv2 or later.
   */
  
  #include <linux/kernel.h>
  #include <linux/interrupt.h>
  #include <linux/clockchips.h>
  #include <linux/clocksource.h>
  #include <linux/bitops.h>
  #include <linux/irq.h>
  #include <linux/clk.h>
  #include <linux/err.h>
  #include <linux/slab.h>
  #include <linux/of.h>
  #include <linux/of_irq.h>
  #include <linux/of_address.h>
  #include <linux/sched_clock.h>
  #include <asm/mach/time.h>
  
  #define SIRFSOC_TIMER_COUNTER_LO	0x0000
  #define SIRFSOC_TIMER_COUNTER_HI	0x0004
  #define SIRFSOC_TIMER_MATCH_0		0x0008
  #define SIRFSOC_TIMER_MATCH_1		0x000C
  #define SIRFSOC_TIMER_MATCH_2		0x0010
  #define SIRFSOC_TIMER_MATCH_3		0x0014
  #define SIRFSOC_TIMER_MATCH_4		0x0018
  #define SIRFSOC_TIMER_MATCH_5		0x001C
  #define SIRFSOC_TIMER_STATUS		0x0020
  #define SIRFSOC_TIMER_INT_EN		0x0024
  #define SIRFSOC_TIMER_WATCHDOG_EN	0x0028
  #define SIRFSOC_TIMER_DIV		0x002C
  #define SIRFSOC_TIMER_LATCH		0x0030
  #define SIRFSOC_TIMER_LATCHED_LO	0x0034
  #define SIRFSOC_TIMER_LATCHED_HI	0x0038
  
  #define SIRFSOC_TIMER_WDT_INDEX		5
  
  #define SIRFSOC_TIMER_LATCH_BIT	 BIT(0)
  
  #define SIRFSOC_TIMER_REG_CNT 11
  
  static const u32 sirfsoc_timer_reg_list[SIRFSOC_TIMER_REG_CNT] = {
  	SIRFSOC_TIMER_MATCH_0, SIRFSOC_TIMER_MATCH_1, SIRFSOC_TIMER_MATCH_2,
  	SIRFSOC_TIMER_MATCH_3, SIRFSOC_TIMER_MATCH_4, SIRFSOC_TIMER_MATCH_5,
  	SIRFSOC_TIMER_INT_EN, SIRFSOC_TIMER_WATCHDOG_EN, SIRFSOC_TIMER_DIV,
  	SIRFSOC_TIMER_LATCHED_LO, SIRFSOC_TIMER_LATCHED_HI,
  };
  
  static u32 sirfsoc_timer_reg_val[SIRFSOC_TIMER_REG_CNT];
  
  static void __iomem *sirfsoc_timer_base;
  
  /* timer0 interrupt handler */
  static irqreturn_t sirfsoc_timer_interrupt(int irq, void *dev_id)
  {
  	struct clock_event_device *ce = dev_id;
  
  	WARN_ON(!(readl_relaxed(sirfsoc_timer_base + SIRFSOC_TIMER_STATUS) & BIT(0)));
  
  	/* clear timer0 interrupt */
  	writel_relaxed(BIT(0), sirfsoc_timer_base + SIRFSOC_TIMER_STATUS);
  
  	ce->event_handler(ce);
  
  	return IRQ_HANDLED;
  }
  
  /* read 64-bit timer counter */
  static cycle_t sirfsoc_timer_read(struct clocksource *cs)
  {
  	u64 cycles;
  
  	/* latch the 64-bit timer counter */
  	writel_relaxed(SIRFSOC_TIMER_LATCH_BIT, sirfsoc_timer_base + SIRFSOC_TIMER_LATCH);
  	cycles = readl_relaxed(sirfsoc_timer_base + SIRFSOC_TIMER_LATCHED_HI);
  	cycles = (cycles << 32) | readl_relaxed(sirfsoc_timer_base + SIRFSOC_TIMER_LATCHED_LO);
  
  	return cycles;
  }
  
  static int sirfsoc_timer_set_next_event(unsigned long delta,
  	struct clock_event_device *ce)
  {
  	unsigned long now, next;
  
  	writel_relaxed(SIRFSOC_TIMER_LATCH_BIT, sirfsoc_timer_base + SIRFSOC_TIMER_LATCH);
  	now = readl_relaxed(sirfsoc_timer_base + SIRFSOC_TIMER_LATCHED_LO);
  	next = now + delta;
  	writel_relaxed(next, sirfsoc_timer_base + SIRFSOC_TIMER_MATCH_0);
  	writel_relaxed(SIRFSOC_TIMER_LATCH_BIT, sirfsoc_timer_base + SIRFSOC_TIMER_LATCH);
  	now = readl_relaxed(sirfsoc_timer_base + SIRFSOC_TIMER_LATCHED_LO);
  
  	return next - now > delta ? -ETIME : 0;
  }
  
  static void sirfsoc_timer_set_mode(enum clock_event_mode mode,
  	struct clock_event_device *ce)
  {
  	u32 val = readl_relaxed(sirfsoc_timer_base + SIRFSOC_TIMER_INT_EN);
  	switch (mode) {
  	case CLOCK_EVT_MODE_PERIODIC:
  		WARN_ON(1);
  		break;
  	case CLOCK_EVT_MODE_ONESHOT:
  		writel_relaxed(val | BIT(0), sirfsoc_timer_base + SIRFSOC_TIMER_INT_EN);
  		break;
  	case CLOCK_EVT_MODE_SHUTDOWN:
  		writel_relaxed(val & ~BIT(0), sirfsoc_timer_base + SIRFSOC_TIMER_INT_EN);
  		break;
  	case CLOCK_EVT_MODE_UNUSED:
  	case CLOCK_EVT_MODE_RESUME:
  		break;
  	}
  }
  
  static void sirfsoc_clocksource_suspend(struct clocksource *cs)
  {
  	int i;
  
  	writel_relaxed(SIRFSOC_TIMER_LATCH_BIT, sirfsoc_timer_base + SIRFSOC_TIMER_LATCH);
  
  	for (i = 0; i < SIRFSOC_TIMER_REG_CNT; i++)
  		sirfsoc_timer_reg_val[i] = readl_relaxed(sirfsoc_timer_base + sirfsoc_timer_reg_list[i]);
  }
  
  static void sirfsoc_clocksource_resume(struct clocksource *cs)
  {
  	int i;
  
  	for (i = 0; i < SIRFSOC_TIMER_REG_CNT - 2; i++)
  		writel_relaxed(sirfsoc_timer_reg_val[i], sirfsoc_timer_base + sirfsoc_timer_reg_list[i]);
  
  	writel_relaxed(sirfsoc_timer_reg_val[SIRFSOC_TIMER_REG_CNT - 2], sirfsoc_timer_base + SIRFSOC_TIMER_COUNTER_LO);
  	writel_relaxed(sirfsoc_timer_reg_val[SIRFSOC_TIMER_REG_CNT - 1], sirfsoc_timer_base + SIRFSOC_TIMER_COUNTER_HI);
  }
  
  static struct clock_event_device sirfsoc_clockevent = {
  	.name = "sirfsoc_clockevent",
  	.rating = 200,
  	.features = CLOCK_EVT_FEAT_ONESHOT,
  	.set_mode = sirfsoc_timer_set_mode,
  	.set_next_event = sirfsoc_timer_set_next_event,
  };
  
  static struct clocksource sirfsoc_clocksource = {
  	.name = "sirfsoc_clocksource",
  	.rating = 200,
  	.mask = CLOCKSOURCE_MASK(64),
  	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
  	.read = sirfsoc_timer_read,
  	.suspend = sirfsoc_clocksource_suspend,
  	.resume = sirfsoc_clocksource_resume,
  };
  
  static struct irqaction sirfsoc_timer_irq = {
  	.name = "sirfsoc_timer0",
  	.flags = IRQF_TIMER,
  	.irq = 0,
  	.handler = sirfsoc_timer_interrupt,
  	.dev_id = &sirfsoc_clockevent,
  };
  
  /* Overwrite weak default sched_clock with more precise one */
  static u64 notrace sirfsoc_read_sched_clock(void)
  {
  	return sirfsoc_timer_read(NULL);
  }
  
  static void __init sirfsoc_clockevent_init(void)
  {
  	sirfsoc_clockevent.cpumask = cpumask_of(0);
  	clockevents_config_and_register(&sirfsoc_clockevent, CLOCK_TICK_RATE,
  					2, -2);
  }
  
  /* initialize the kernel jiffy timer source */
  static void __init sirfsoc_prima2_timer_init(struct device_node *np)
  {
  	unsigned long rate;
  	struct clk *clk;
  
  	/* timer's input clock is io clock */
  	clk = clk_get_sys("io", NULL);
  
  	BUG_ON(IS_ERR(clk));
  
  	rate = clk_get_rate(clk);
  
  	BUG_ON(rate < CLOCK_TICK_RATE);
  	BUG_ON(rate % CLOCK_TICK_RATE);
  
  	sirfsoc_timer_base = of_iomap(np, 0);
  	if (!sirfsoc_timer_base)
  		panic("unable to map timer cpu registers
  ");
  
  	sirfsoc_timer_irq.irq = irq_of_parse_and_map(np, 0);
  
  	writel_relaxed(rate / CLOCK_TICK_RATE / 2 - 1, sirfsoc_timer_base + SIRFSOC_TIMER_DIV);
  	writel_relaxed(0, sirfsoc_timer_base + SIRFSOC_TIMER_COUNTER_LO);
  	writel_relaxed(0, sirfsoc_timer_base + SIRFSOC_TIMER_COUNTER_HI);
  	writel_relaxed(BIT(0), sirfsoc_timer_base + SIRFSOC_TIMER_STATUS);
  
  	BUG_ON(clocksource_register_hz(&sirfsoc_clocksource, CLOCK_TICK_RATE));
  
  	sched_clock_register(sirfsoc_read_sched_clock, 64, CLOCK_TICK_RATE);
  
  	BUG_ON(setup_irq(sirfsoc_timer_irq.irq, &sirfsoc_timer_irq));
  
  	sirfsoc_clockevent_init();
  }
  CLOCKSOURCE_OF_DECLARE(sirfsoc_prima2_timer, "sirf,prima2-tick", sirfsoc_prima2_timer_init);