/*
 * Copyright (C) 2005-2013 Imagination Technologies Ltd.
 *
 * 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.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 * Support for Meta per-thread timers.
 *
 * Meta hardware threads have 2 timers. The background timer (TXTIMER) is used
 * as a free-running time base (hz clocksource), and the interrupt timer
 * (TXTIMERI) is used for the timer interrupt (clock event). Both counters
 * traditionally count at approximately 1MHz.
 */

#include <clocksource/metag_generic.h>
#include <linux/cpu.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/interrupt.h>

#include <asm/clock.h>
#include <asm/hwthread.h>
#include <asm/core_reg.h>
#include <asm/metag_mem.h>
#include <asm/tbx.h>

#define HARDWARE_FREQ           1000000 /* 1MHz */
#define HARDWARE_DIV            1       /* divide by 1 = 1MHz clock */
#define HARDWARE_TO_NS_SHIFT    10      /* convert ticks to ns */

static unsigned int hwtimer_freq = HARDWARE_FREQ;
static DEFINE_PER_CPU(struct clock_event_device, local_clockevent);
static DEFINE_PER_CPU(char [11], local_clockevent_name);

static int metag_timer_set_next_event(unsigned long delta,
                                      struct clock_event_device *dev)
{
        __core_reg_set(TXTIMERI, -delta);
        return 0;
}

static void metag_timer_set_mode(enum clock_event_mode mode,
                                 struct clock_event_device *evt)
{
        switch (mode) {
        case CLOCK_EVT_MODE_ONESHOT:
        case CLOCK_EVT_MODE_RESUME:
                break;

        case CLOCK_EVT_MODE_SHUTDOWN:
                /* We should disable the IRQ here */
                break;

        case CLOCK_EVT_MODE_PERIODIC:
        case CLOCK_EVT_MODE_UNUSED:
                WARN_ON(1);
                break;
        };
}

static cycle_t metag_clocksource_read(struct clocksource *cs)
{
        return __core_reg_get(TXTIMER);
}

static struct clocksource clocksource_metag = {
        .name = "META",
        .rating = 200,
        .mask = CLOCKSOURCE_MASK(32),
        .read = metag_clocksource_read,
        .flags = CLOCK_SOURCE_IS_CONTINUOUS,
};

static irqreturn_t metag_timer_interrupt(int irq, void *dummy)
{
        struct clock_event_device *evt = &__get_cpu_var(local_clockevent);

        evt->event_handler(evt);

        return IRQ_HANDLED;
}

static struct irqaction metag_timer_irq = {
        .name = "META core timer",
        .handler = metag_timer_interrupt,
        .flags = IRQF_TIMER | IRQF_IRQPOLL | IRQF_PERCPU,
};

unsigned long long sched_clock(void)
{
        unsigned long long ticks = __core_reg_get(TXTIMER);
        return ticks << HARDWARE_TO_NS_SHIFT;
}

static void arch_timer_setup(unsigned int cpu)
{
        unsigned int txdivtime;
        struct clock_event_device *clk = &per_cpu(local_clockevent, cpu);
        char *name = per_cpu(local_clockevent_name, cpu);

        txdivtime = __core_reg_get(TXDIVTIME);

        txdivtime &= ~TXDIVTIME_DIV_BITS;
        txdivtime |= (HARDWARE_DIV & TXDIVTIME_DIV_BITS);

        __core_reg_set(TXDIVTIME, txdivtime);

        sprintf(name, "META %d", cpu);
        clk->name = name;
        clk->features = CLOCK_EVT_FEAT_ONESHOT,

        clk->rating = 200,
        clk->shift = 12,
        clk->irq = tbisig_map(TBID_SIGNUM_TRT),
        clk->set_mode = metag_timer_set_mode,
        clk->set_next_event = metag_timer_set_next_event,

        clk->mult = div_sc(hwtimer_freq, NSEC_PER_SEC, clk->shift);
        clk->max_delta_ns = clockevent_delta2ns(0x7fffffff, clk);
        clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
        clk->cpumask = cpumask_of(cpu);

        clockevents_register_device(clk);

        /*
         * For all non-boot CPUs we need to synchronize our free
         * running clock (TXTIMER) with the boot CPU's clock.
         *
         * While this won't be accurate, it should be close enough.
         */
        if (cpu) {
                unsigned int thread0 = cpu_2_hwthread_id[0];
                unsigned long val;

                val = core_reg_read(TXUCT_ID, TXTIMER_REGNUM, thread0);
                __core_reg_set(TXTIMER, val);
        }
}

static int arch_timer_cpu_notify(struct notifier_block *self,
                                           unsigned long action, void *hcpu)
{
        int cpu = (long)hcpu;

        switch (action) {
        case CPU_STARTING:
        case CPU_STARTING_FROZEN:
                arch_timer_setup(cpu);
                break;
        }

        return NOTIFY_OK;
}

static struct notifier_block arch_timer_cpu_nb = {
        .notifier_call = arch_timer_cpu_notify,
};

int __init metag_generic_timer_init(void)
{
        /*
         * On Meta 2 SoCs, the actual frequency of the timer is based on the
         * Meta core clock speed divided by an integer, so it is only
         * approximately 1MHz. Calculating the real frequency here drastically
         * reduces clock skew on these SoCs.
         */
#ifdef CONFIG_METAG_META21
        hwtimer_freq = get_coreclock() / (metag_in32(EXPAND_TIMER_DIV) + 1);
#endif
        pr_info("Timer frequency: %u Hz\n", hwtimer_freq);

        clocksource_register_hz(&clocksource_metag, hwtimer_freq);

        setup_irq(tbisig_map(TBID_SIGNUM_TRT), &metag_timer_irq);

        /* Configure timer on boot CPU */
        arch_timer_setup(smp_processor_id());

        /* Hook cpu boot to configure other CPU's timers */
        register_cpu_notifier(&arch_timer_cpu_nb);

        return 0;
}