/*
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 *
 * 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.
 *
 * vineetg: Jan 1011
 *  -sched_clock( ) no longer jiffies based. Uses the same clocksource
 *   as gtod
 *
 * Rajeshwarr/Vineetg: Mar 2008
 *  -Implemented CONFIG_GENERIC_TIME (rather deleted arch specific code)
 *   for arch independent gettimeofday()
 *  -Implemented CONFIG_GENERIC_CLOCKEVENTS as base for hrtimers
 *
 * Vineetg: Mar 2008: Forked off from time.c which now is time-jiff.c
 */

#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/timex.h>
#include <linux/profile.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/board/soc.h>
#include <asm/arcregs.h>
#include <asm/event-log.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>

#include <qtn/topaz_hbm.h>
/* ARC700 has two 32bit independent prog Timers: TIMER0 and TIMER1
 * Each can programmed to go from @count to @limit and optionally
 * interrupt when that happens
 *
 * We've designated TIMER0 for events (clockevents)
 * while TIMER1 for free running (clocksource)
 */

/******************************************************************
 * Hardware Interface routines to program the ARC TIMERs
 ******************************************************************/

/*
 * Arm the timer to interrupt after @limit cycles
 */
static void arc_timer0_setup_event(unsigned int limit)
{
    /* setup start and end markers */
    write_new_aux_reg(ARC_REG_TIMER0_LIMIT, limit);
    write_new_aux_reg(ARC_REG_TIMER0_CNT, 0);     // start from 0

    /* IE: Interrupt on count = limit,
     * NH: Count cycles only when CPU running (NOT Halted)
     */
    write_new_aux_reg(ARC_REG_TIMER0_CTRL, TIMER_CTRL_IE|TIMER_CTRL_NH);
}

/*
 * Acknowledge the interrupt & enable/disable the interrupt
 */
static void arc_timer0_ack_event(unsigned int irq_reenable)
{
    /* 1. Ack the interrupt by writing to CTRL reg.
     *    Any write will cause intr to be ack, however it has to be one of
     *    writable bits (NH: Count when not halted)
     * 2. If required by caller, re-arm timer to Interrupt at the end of
     *    next cycle.
     *
     * Small optimisation:
     * Normal code would have been
     *  if (irq_reenable) CTRL_REG = (IE | NH); else CTRL_REG = NH;
     * However since IE is BIT0 we can fold the branch
     */
    write_new_aux_reg(ARC_REG_TIMER0_CTRL, irq_reenable | TIMER_CTRL_NH);
}

/*
 * Arm the timer to keep counting monotonically
 */
static void arc_timer1_setup_free_flow(unsigned int limit)
{
    /* although for free flowing case, limit would alway be max 32 bits
     * still we've kept the interface open, just in case ...
     */
    write_new_aux_reg(ARC_REG_TIMER1_LIMIT, limit);     // caller specifies
    write_new_aux_reg(ARC_REG_TIMER1_CNT, 0);           // start from 0
    write_new_aux_reg(ARC_REG_TIMER1_CTRL, TIMER_CTRL_NH);
}

/********** Clock Source Device *********/

static cycle_t cycle_read_t1(struct clocksource *cs)
{
    return (cycle_t)read_new_aux_reg(ARC_REG_TIMER1_CNT);
}

static struct clocksource clocksource_t1 = {
    .name   = "ARC Timer1",
    .rating = 300,
    .read   = cycle_read_t1,
    .mask   = CLOCKSOURCE_MASK(32),
    .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
};

static void __init arc_clocksource_init(void)
{
    u64 temp;
    u32 shift;
    struct clocksource *cs = &clocksource_t1;

    /* Find a shift value */
    for (shift = 32; shift > 0; shift--) {
        temp = (u64) NSEC_PER_SEC << shift;
        do_div(temp, CONFIG_ARC700_CLK);
        if ((temp >> 32) == 0)
            break;
    }
    cs->shift = shift;
    cs->mult = (u32) temp;

    arc_timer1_setup_free_flow(0xFFFFFFFF);

    clocksource_register(&clocksource_t1);
}

/********** Clock Event Device *********/

struct clock_event_device __sram_data arc_clockevent_device;

static irqreturn_t timer_irq_handler(int irq, void *dev_id);

static struct irqaction arc_timer_irq = {
    .name       = "ARC Timer0",
    .flags      = 0,
    .handler    = timer_irq_handler,
    .dev_id     = &arc_clockevent_device,
};

irqreturn_t __sram_text timer_irq_handler(int irq, void *dev_id)
{
    struct clock_event_device *evt = dev_id;

    pet_watchdog_timer();
    arc_timer0_ack_event(evt->mode == CLOCK_EVT_MODE_PERIODIC);
    topaz_hbm_filter_txdone_pool();
    evt->event_handler(evt);
    return IRQ_HANDLED;
}


static int arc_next_event(unsigned long delta, struct clock_event_device *dev)
{
    arc_timer0_setup_event(delta);
    return 0;
}

static void arc_set_mode(enum clock_event_mode mode,
                                struct clock_event_device *dev)
{
    printk("clockevent mode switch to [%d]\n",mode);
    switch (mode) {
        case CLOCK_EVT_MODE_PERIODIC:
                arc_timer0_setup_event(CONFIG_ARC700_CLK / HZ);
                break;
        case CLOCK_EVT_MODE_ONESHOT:
                break;
        default:
                break;
    }

    return;
}

static void __cpuinit arc_clockevent_init(void)
{
    u64 temp;
    u32 shift;
    struct clock_event_device *cd = &arc_clockevent_device;

    cd->name = "ARC Clock";
    cd->features = CLOCK_EVT_FEAT_ONESHOT;
    cd->features |= CLOCK_EVT_FEAT_PERIODIC;
    cd->mode = CLOCK_EVT_MODE_UNUSED;

    /* Find a shift value */
    for (shift = 32; shift > 0; shift--) {
        temp = (u64) CONFIG_ARC700_CLK << shift;
        do_div(temp, NSEC_PER_SEC);
        if ((temp >> 32) == 0)
            break;
    }
    cd->shift   = shift;
    cd->mult    = (u32) temp;

    /* configuring min_delta_ns as nanoseconds for 1 tick
     * and max_delta_ns as 0xffffffff, max limit value accepted by hardware
     * for any event at less than the min_delta_ns is rounded to this time and
     * for any event at more than the max_delta_ns we configure the max and end
     * up having intermediate ticks before the event
     * This is taken care in clockevent_program_event
     */

    cd->max_delta_ns = clockevent_delta2ns(0xffffffff, cd);
    cd->min_delta_ns = clockevent_delta2ns(0x1, cd);

    cd->rating  = 300;
    cd->irq     = TIMER0_INT;
    cd->cpumask = cpumask_of(0);
    cd->set_next_event  = arc_next_event;
    cd->set_mode        = arc_set_mode;

    clockevents_register_device(cd);

    setup_irq(TIMER0_INT, &arc_timer_irq);
}


void __init time_init(void)
{
    extern unsigned long clk_speed;

    if (clk_speed != CONFIG_ARC700_CLK)
        panic("CONFIG_ARC700_CLK doesn't match corresp boot param\n");

    xtime.tv_sec = 0;
    xtime.tv_nsec = 0;
    set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);

    arc_clocksource_init();
    arc_clockevent_init();
    init_watchdog_timer();
}

static int arc_finished_booting;

static int __init arc_clocksource_done_booting(void)
{
	arc_finished_booting = 1;
	return 0;
}

fs_initcall(arc_clocksource_done_booting);