// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2016-17 Synopsys, Inc. (www.synopsys.com)
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 */

/* ARC700 has two 32bit independent prog Timers: TIMER0 and TIMER1, Each can be
 * programmed to go from @count to @limit and optionally interrupt.
 * We've designated TIMER0 for clockevents and TIMER1 for clocksource
 *
 * ARCv2 based HS38 cores have RTC (in-core) and GFRC (inside ARConnect/MCIP)
 * which are suitable for UP and SMP based clocksources respectively
 */

#include <linux/interrupt.h>
#include <linux/bits.h>
#include <linux/clk.h>
#include <linux/clk-provider.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/cpu.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/sched_clock.h>

#include <soc/arc/timers.h>
#include <soc/arc/mcip.h>


static unsigned long arc_timer_freq;

static int noinline arc_get_timer_clk(struct device_node *node)
{
        struct clk *clk;
        int ret;

        clk = of_clk_get(node, 0);
        if (IS_ERR(clk)) {
                pr_err("timer missing clk\n");
                return PTR_ERR(clk);
        }

        ret = clk_prepare_enable(clk);
        if (ret) {
                pr_err("Couldn't enable parent clk\n");
                return ret;
        }

        arc_timer_freq = clk_get_rate(clk);

        return 0;
}

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

#ifdef CONFIG_ARC_TIMERS_64BIT

static u64 arc_read_gfrc(struct clocksource *cs)
{
        unsigned long flags;
        u32 l, h;

        /*
         * From a programming model pov, there seems to be just one instance of
         * MCIP_CMD/MCIP_READBACK however micro-architecturally there's
         * an instance PER ARC CORE (not per cluster), and there are dedicated
         * hardware decode logic (per core) inside ARConnect to handle
         * simultaneous read/write accesses from cores via those two registers.
         * So several concurrent commands to ARConnect are OK if they are
         * trying to access two different sub-components (like GFRC,
         * inter-core interrupt, etc...). HW also supports simultaneously
         * accessing GFRC by multiple cores.
         * That's why it is safe to disable hard interrupts on the local CPU
         * before access to GFRC instead of taking global MCIP spinlock
         * defined in arch/arc/kernel/mcip.c
         */
        local_irq_save(flags);

        __mcip_cmd(CMD_GFRC_READ_LO, 0);
        l = read_aux_reg(ARC_REG_MCIP_READBACK);

        __mcip_cmd(CMD_GFRC_READ_HI, 0);
        h = read_aux_reg(ARC_REG_MCIP_READBACK);

        local_irq_restore(flags);

        return (((u64)h) << 32) | l;
}

static notrace u64 arc_gfrc_clock_read(void)
{
        return arc_read_gfrc(NULL);
}

static struct clocksource arc_counter_gfrc = {
        .name   = "ARConnect GFRC",
        .rating = 400,
        .read   = arc_read_gfrc,
        .mask   = CLOCKSOURCE_MASK(64),
        .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
};

static int __init arc_cs_setup_gfrc(struct device_node *node)
{
        struct mcip_bcr mp;
        int ret;

        READ_BCR(ARC_REG_MCIP_BCR, mp);
        if (!mp.gfrc) {
                pr_warn("Global-64-bit-Ctr clocksource not detected\n");
                return -ENXIO;
        }

        ret = arc_get_timer_clk(node);
        if (ret)
                return ret;

        sched_clock_register(arc_gfrc_clock_read, 64, arc_timer_freq);

        return clocksource_register_hz(&arc_counter_gfrc, arc_timer_freq);
}
TIMER_OF_DECLARE(arc_gfrc, "snps,archs-timer-gfrc", arc_cs_setup_gfrc);

#define AUX_RTC_CTRL    0x103
#define AUX_RTC_LOW     0x104
#define AUX_RTC_HIGH    0x105

static u64 arc_read_rtc(struct clocksource *cs)
{
        unsigned long status;
        u32 l, h;

        /*
         * hardware has an internal state machine which tracks readout of
         * low/high and updates the CTRL.status if
         *  - interrupt/exception taken between the two reads
         *  - high increments after low has been read
         */
        do {
                l = read_aux_reg(AUX_RTC_LOW);
                h = read_aux_reg(AUX_RTC_HIGH);
                status = read_aux_reg(AUX_RTC_CTRL);
        } while (!(status & BIT(31)));

        return (((u64)h) << 32) | l;
}

static notrace u64 arc_rtc_clock_read(void)
{
        return arc_read_rtc(NULL);
}

static struct clocksource arc_counter_rtc = {
        .name   = "ARCv2 RTC",
        .rating = 350,
        .read   = arc_read_rtc,
        .mask   = CLOCKSOURCE_MASK(64),
        .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
};

static int __init arc_cs_setup_rtc(struct device_node *node)
{
        struct bcr_timer timer;
        int ret;

        READ_BCR(ARC_REG_TIMERS_BCR, timer);
        if (!timer.rtc) {
                pr_warn("Local-64-bit-Ctr clocksource not detected\n");
                return -ENXIO;
        }

        /* Local to CPU hence not usable in SMP */
        if (IS_ENABLED(CONFIG_SMP)) {
                pr_warn("Local-64-bit-Ctr not usable in SMP\n");
                return -EINVAL;
        }

        ret = arc_get_timer_clk(node);
        if (ret)
                return ret;

        write_aux_reg(AUX_RTC_CTRL, 1);

        sched_clock_register(arc_rtc_clock_read, 64, arc_timer_freq);

        return clocksource_register_hz(&arc_counter_rtc, arc_timer_freq);
}
TIMER_OF_DECLARE(arc_rtc, "snps,archs-timer-rtc", arc_cs_setup_rtc);

#endif

/*
 * 32bit TIMER1 to keep counting monotonically and wraparound
 */

static u64 arc_read_timer1(struct clocksource *cs)
{
        return (u64) read_aux_reg(ARC_REG_TIMER1_CNT);
}

static notrace u64 arc_timer1_clock_read(void)
{
        return arc_read_timer1(NULL);
}

static struct clocksource arc_counter_timer1 = {
        .name   = "ARC Timer1",
        .rating = 300,
        .read   = arc_read_timer1,
        .mask   = CLOCKSOURCE_MASK(32),
        .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
};

static int __init arc_cs_setup_timer1(struct device_node *node)
{
        int ret;

        /* Local to CPU hence not usable in SMP */
        if (IS_ENABLED(CONFIG_SMP))
                return -EINVAL;

        ret = arc_get_timer_clk(node);
        if (ret)
                return ret;

        write_aux_reg(ARC_REG_TIMER1_LIMIT, ARC_TIMERN_MAX);
        write_aux_reg(ARC_REG_TIMER1_CNT, 0);
        write_aux_reg(ARC_REG_TIMER1_CTRL, ARC_TIMER_CTRL_NH);

        sched_clock_register(arc_timer1_clock_read, 32, arc_timer_freq);

        return clocksource_register_hz(&arc_counter_timer1, arc_timer_freq);
}

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

static int arc_timer_irq;

/*
 * Arm the timer to interrupt after @cycles
 * The distinction for oneshot/periodic is done in arc_event_timer_ack() below
 */
static void arc_timer_event_setup(unsigned int cycles)
{
        write_aux_reg(ARC_REG_TIMER0_LIMIT, cycles);
        write_aux_reg(ARC_REG_TIMER0_CNT, 0);   /* start from 0 */

        write_aux_reg(ARC_REG_TIMER0_CTRL, ARC_TIMER_CTRL_IE | ARC_TIMER_CTRL_NH);
}


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

static int arc_clkevent_set_periodic(struct clock_event_device *dev)
{
        /*
         * At X Hz, 1 sec = 1000ms -> X cycles;
         *                    10ms -> X / 100 cycles
         */
        arc_timer_event_setup(arc_timer_freq / HZ);
        return 0;
}

static DEFINE_PER_CPU(struct clock_event_device, arc_clockevent_device) = {
        .name                   = "ARC Timer0",
        .features               = CLOCK_EVT_FEAT_ONESHOT |
                                  CLOCK_EVT_FEAT_PERIODIC,
        .rating                 = 300,
        .set_next_event         = arc_clkevent_set_next_event,
        .set_state_periodic     = arc_clkevent_set_periodic,
};

static irqreturn_t timer_irq_handler(int irq, void *dev_id)
{
        /*
         * Note that generic IRQ core could have passed @evt for @dev_id if
         * irq_set_chip_and_handler() asked for handle_percpu_devid_irq()
         */
        struct clock_event_device *evt = this_cpu_ptr(&arc_clockevent_device);
        int irq_reenable = clockevent_state_periodic(evt);

        /*
         * 1. ACK the interrupt
         *    - For ARC700, any write to CTRL reg ACKs it, so just rewrite
         *      Count when [N]ot [H]alted bit.
         *    - For HS3x, it is a bit subtle. On taken count-down interrupt,
         *      IP bit [3] is set, which needs to be cleared for ACK'ing.
         *      The write below can only update the other two bits, hence
         *      explicitly clears IP bit
         * 2. Re-arm interrupt if periodic by writing to IE bit [0]
         */
        write_aux_reg(ARC_REG_TIMER0_CTRL, irq_reenable | ARC_TIMER_CTRL_NH);

        evt->event_handler(evt);

        return IRQ_HANDLED;
}


static int arc_timer_starting_cpu(unsigned int cpu)
{
        struct clock_event_device *evt = this_cpu_ptr(&arc_clockevent_device);

        evt->cpumask = cpumask_of(smp_processor_id());

        clockevents_config_and_register(evt, arc_timer_freq, 0, ARC_TIMERN_MAX);
        enable_percpu_irq(arc_timer_irq, 0);
        return 0;
}

static int arc_timer_dying_cpu(unsigned int cpu)
{
        disable_percpu_irq(arc_timer_irq);
        return 0;
}

/*
 * clockevent setup for boot CPU
 */
static int __init arc_clockevent_setup(struct device_node *node)
{
        struct clock_event_device *evt = this_cpu_ptr(&arc_clockevent_device);
        int ret;

        arc_timer_irq = irq_of_parse_and_map(node, 0);
        if (arc_timer_irq <= 0) {
                pr_err("clockevent: missing irq\n");
                return -EINVAL;
        }

        ret = arc_get_timer_clk(node);
        if (ret)
                return ret;

        /* Needs apriori irq_set_percpu_devid() done in intc map function */
        ret = request_percpu_irq(arc_timer_irq, timer_irq_handler,
                                 "Timer0 (per-cpu-tick)", evt);
        if (ret) {
                pr_err("clockevent: unable to request irq\n");
                return ret;
        }

        ret = cpuhp_setup_state(CPUHP_AP_ARC_TIMER_STARTING,
                                "clockevents/arc/timer:starting",
                                arc_timer_starting_cpu,
                                arc_timer_dying_cpu);
        if (ret) {
                pr_err("Failed to setup hotplug state\n");
                return ret;
        }
        return 0;
}

static int __init arc_of_timer_init(struct device_node *np)
{
        static int init_count = 0;
        int ret;

        if (!init_count) {
                init_count = 1;
                ret = arc_clockevent_setup(np);
        } else {
                ret = arc_cs_setup_timer1(np);
        }

        return ret;
}
TIMER_OF_DECLARE(arc_clkevt, "snps,arc-timer", arc_of_timer_init);