/*
 * Copyright (C) 2010 Google, Inc.
 *
 * Author:
 *      Colin Cross <ccross@google.com>
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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.
 *
 */

#include <linux/init.h>
#include <linux/err.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>

#include <asm/mach/time.h>
#include <asm/smp_twd.h>
#include <asm/sched_clock.h>

#define RTC_SECONDS            0x08
#define RTC_SHADOW_SECONDS     0x0c
#define RTC_MILLISECONDS       0x10

#define TIMERUS_CNTR_1US 0x10
#define TIMERUS_USEC_CFG 0x14
#define TIMERUS_CNTR_FREEZE 0x4c

#define TIMER1_BASE 0x0
#define TIMER2_BASE 0x8
#define TIMER3_BASE 0x50
#define TIMER4_BASE 0x58

#define TIMER_PTV 0x0
#define TIMER_PCR 0x4

static void __iomem *timer_reg_base;
static void __iomem *rtc_base;

static struct timespec persistent_ts;
static u64 persistent_ms, last_persistent_ms;

#define timer_writel(value, reg) \
        __raw_writel(value, timer_reg_base + (reg))
#define timer_readl(reg) \
        __raw_readl(timer_reg_base + (reg))

static int tegra_timer_set_next_event(unsigned long cycles,
                                         struct clock_event_device *evt)
{
        u32 reg;

        reg = 0x80000000 | ((cycles > 1) ? (cycles-1) : 0);
        timer_writel(reg, TIMER3_BASE + TIMER_PTV);

        return 0;
}

static void tegra_timer_set_mode(enum clock_event_mode mode,
                                    struct clock_event_device *evt)
{
        u32 reg;

        timer_writel(0, TIMER3_BASE + TIMER_PTV);

        switch (mode) {
        case CLOCK_EVT_MODE_PERIODIC:
                reg = 0xC0000000 | ((1000000/HZ)-1);
                timer_writel(reg, TIMER3_BASE + TIMER_PTV);
                break;
        case CLOCK_EVT_MODE_ONESHOT:
                break;
        case CLOCK_EVT_MODE_UNUSED:
        case CLOCK_EVT_MODE_SHUTDOWN:
        case CLOCK_EVT_MODE_RESUME:
                break;
        }
}

static struct clock_event_device tegra_clockevent = {
        .name           = "timer0",
        .rating         = 300,
        .features       = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
        .set_next_event = tegra_timer_set_next_event,
        .set_mode       = tegra_timer_set_mode,
};

static u32 notrace tegra_read_sched_clock(void)
{
        return timer_readl(TIMERUS_CNTR_1US);
}

/*
 * tegra_rtc_read - Reads the Tegra RTC registers
 * Care must be taken that this funciton is not called while the
 * tegra_rtc driver could be executing to avoid race conditions
 * on the RTC shadow register
 */
static u64 tegra_rtc_read_ms(void)
{
        u32 ms = readl(rtc_base + RTC_MILLISECONDS);
        u32 s = readl(rtc_base + RTC_SHADOW_SECONDS);
        return (u64)s * MSEC_PER_SEC + ms;
}

/*
 * tegra_read_persistent_clock -  Return time from a persistent clock.
 *
 * Reads the time from a source which isn't disabled during PM, the
 * 32k sync timer.  Convert the cycles elapsed since last read into
 * nsecs and adds to a monotonically increasing timespec.
 * Care must be taken that this funciton is not called while the
 * tegra_rtc driver could be executing to avoid race conditions
 * on the RTC shadow register
 */
static void tegra_read_persistent_clock(struct timespec *ts)
{
        u64 delta;
        struct timespec *tsp = &persistent_ts;

        last_persistent_ms = persistent_ms;
        persistent_ms = tegra_rtc_read_ms();
        delta = persistent_ms - last_persistent_ms;

        timespec_add_ns(tsp, delta * NSEC_PER_MSEC);
        *ts = *tsp;
}

static irqreturn_t tegra_timer_interrupt(int irq, void *dev_id)
{
        struct clock_event_device *evt = (struct clock_event_device *)dev_id;
        timer_writel(1<<30, TIMER3_BASE + TIMER_PCR);
        evt->event_handler(evt);
        return IRQ_HANDLED;
}

static struct irqaction tegra_timer_irq = {
        .name           = "timer0",
        .flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_TRIGGER_HIGH,
        .handler        = tegra_timer_interrupt,
        .dev_id         = &tegra_clockevent,
};

static const struct of_device_id timer_match[] __initconst = {
        { .compatible = "nvidia,tegra20-timer" },
        {}
};

static const struct of_device_id rtc_match[] __initconst = {
        { .compatible = "nvidia,tegra20-rtc" },
        {}
};

static void __init tegra20_init_timer(void)
{
        struct device_node *np;
        struct clk *clk;
        unsigned long rate;
        int ret;

        np = of_find_matching_node(NULL, timer_match);
        if (!np) {
                pr_err("Failed to find timer DT node\n");
                BUG();
        }

        timer_reg_base = of_iomap(np, 0);
        if (!timer_reg_base) {
                pr_err("Can't map timer registers\n");
                BUG();
        }

        tegra_timer_irq.irq = irq_of_parse_and_map(np, 2);
        if (tegra_timer_irq.irq <= 0) {
                pr_err("Failed to map timer IRQ\n");
                BUG();
        }

        clk = clk_get_sys("timer", NULL);
        if (IS_ERR(clk)) {
                pr_warn("Unable to get timer clock. Assuming 12Mhz input clock.\n");
                rate = 12000000;
        } else {
                clk_prepare_enable(clk);
                rate = clk_get_rate(clk);
        }

        of_node_put(np);

        np = of_find_matching_node(NULL, rtc_match);
        if (!np) {
                pr_err("Failed to find RTC DT node\n");
                BUG();
        }

        rtc_base = of_iomap(np, 0);
        if (!rtc_base) {
                pr_err("Can't map RTC registers");
                BUG();
        }

        /*
         * rtc registers are used by read_persistent_clock, keep the rtc clock
         * enabled
         */
        clk = clk_get_sys("rtc-tegra", NULL);
        if (IS_ERR(clk))
                pr_warn("Unable to get rtc-tegra clock\n");
        else
                clk_prepare_enable(clk);

        of_node_put(np);

        switch (rate) {
        case 12000000:
                timer_writel(0x000b, TIMERUS_USEC_CFG);
                break;
        case 13000000:
                timer_writel(0x000c, TIMERUS_USEC_CFG);
                break;
        case 19200000:
                timer_writel(0x045f, TIMERUS_USEC_CFG);
                break;
        case 26000000:
                timer_writel(0x0019, TIMERUS_USEC_CFG);
                break;
        default:
                WARN(1, "Unknown clock rate");
        }

        setup_sched_clock(tegra_read_sched_clock, 32, 1000000);

        if (clocksource_mmio_init(timer_reg_base + TIMERUS_CNTR_1US,
                "timer_us", 1000000, 300, 32, clocksource_mmio_readl_up)) {
                pr_err("Failed to register clocksource\n");
                BUG();
        }

        ret = setup_irq(tegra_timer_irq.irq, &tegra_timer_irq);
        if (ret) {
                pr_err("Failed to register timer IRQ: %d\n", ret);
                BUG();
        }

        tegra_clockevent.cpumask = cpu_all_mask;
        tegra_clockevent.irq = tegra_timer_irq.irq;
        clockevents_config_and_register(&tegra_clockevent, 1000000,
                                        0x1, 0x1fffffff);
#ifdef CONFIG_HAVE_ARM_TWD
        twd_local_timer_of_register();
#endif
        register_persistent_clock(NULL, tegra_read_persistent_clock);
}
CLOCKSOURCE_OF_DECLARE(tegra20, "nvidia,tegra20-timer", tegra20_init_timer);

#ifdef CONFIG_PM
static u32 usec_config;

void tegra_timer_suspend(void)
{
        usec_config = timer_readl(TIMERUS_USEC_CFG);
}

void tegra_timer_resume(void)
{
        timer_writel(usec_config, TIMERUS_USEC_CFG);
}
#endif