/*
 * 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_address.h>
#include <mach/map.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)

static void __iomem *sirfsoc_timer_base;
static void __init sirfsoc_of_timer_map(void);

/* 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 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,
};

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 */
unsigned long long notrace sched_clock(void)
{
	static int is_mapped = 0;

	/*
	 * sched_clock is called earlier than .init of sys_timer
	 * if we map timer memory in .init of sys_timer, system
	 * will panic due to illegal memory access
	 */
	if(!is_mapped) {
		sirfsoc_of_timer_map();
		is_mapped = 1;
	}

	return sirfsoc_timer_read(NULL) * (NSEC_PER_SEC / CLOCK_TICK_RATE);
}

static void __init sirfsoc_clockevent_init(void)
{
	clockevents_calc_mult_shift(&sirfsoc_clockevent, CLOCK_TICK_RATE, 60);

	sirfsoc_clockevent.max_delta_ns =
		clockevent_delta2ns(-2, &sirfsoc_clockevent);
	sirfsoc_clockevent.min_delta_ns =
		clockevent_delta2ns(2, &sirfsoc_clockevent);

	sirfsoc_clockevent.cpumask = cpumask_of(0);
	clockevents_register_device(&sirfsoc_clockevent);
}

/* initialize the kernel jiffy timer source */
static void __init sirfsoc_timer_init(void)
{
	unsigned long rate;

	/* timer's input clock is io clock */
	struct clk *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);

	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));

	BUG_ON(setup_irq(sirfsoc_timer_irq.irq, &sirfsoc_timer_irq));

	sirfsoc_clockevent_init();
}

static struct of_device_id timer_ids[] = {
	{ .compatible = "sirf,prima2-tick" },
	{},
};

static void __init sirfsoc_of_timer_map(void)
{
	struct device_node *np;
	const unsigned int *intspec;

	np = of_find_matching_node(NULL, timer_ids);
	if (!np)
		panic("unable to find compatible timer node in dtb\n");
	sirfsoc_timer_base = of_iomap(np, 0);
	if (!sirfsoc_timer_base)
		panic("unable to map timer cpu registers\n");

	/* Get the interrupts property */
	intspec = of_get_property(np, "interrupts", NULL);
	BUG_ON(!intspec);
	sirfsoc_timer_irq.irq = be32_to_cpup(intspec);

	of_node_put(np);
}

struct sys_timer sirfsoc_timer = {
	.init = sirfsoc_timer_init,
};