// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/arch/arm/kernel/smp_twd.c
 *
 *  Copyright (C) 2002 ARM Ltd.
 *  All Rights Reserved
 */
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/clk.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/smp.h>
#include <linux/jiffies.h>
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/of_irq.h>
#include <linux/of_address.h>

#include <asm/smp_twd.h>

/* set up by the platform code */
static void __iomem *twd_base;

static struct clk *twd_clk;
static unsigned long twd_timer_rate;
static DEFINE_PER_CPU(bool, percpu_setup_called);

static struct clock_event_device __percpu *twd_evt;
static unsigned int twd_features =
                CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
static int twd_ppi;

static int twd_shutdown(struct clock_event_device *clk)
{
        writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
        return 0;
}

static int twd_set_oneshot(struct clock_event_device *clk)
{
        /* period set, and timer enabled in 'next_event' hook */
        writel_relaxed(TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT,
                       twd_base + TWD_TIMER_CONTROL);
        return 0;
}

static int twd_set_periodic(struct clock_event_device *clk)
{
        unsigned long ctrl = TWD_TIMER_CONTROL_ENABLE |
                             TWD_TIMER_CONTROL_IT_ENABLE |
                             TWD_TIMER_CONTROL_PERIODIC;

        writel_relaxed(DIV_ROUND_CLOSEST(twd_timer_rate, HZ),
                       twd_base + TWD_TIMER_LOAD);
        writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL);
        return 0;
}

static int twd_set_next_event(unsigned long evt,
                        struct clock_event_device *unused)
{
        unsigned long ctrl = readl_relaxed(twd_base + TWD_TIMER_CONTROL);

        ctrl |= TWD_TIMER_CONTROL_ENABLE;

        writel_relaxed(evt, twd_base + TWD_TIMER_COUNTER);
        writel_relaxed(ctrl, twd_base + TWD_TIMER_CONTROL);

        return 0;
}

/*
 * local_timer_ack: checks for a local timer interrupt.
 *
 * If a local timer interrupt has occurred, acknowledge and return 1.
 * Otherwise, return 0.
 */
static int twd_timer_ack(void)
{
        if (readl_relaxed(twd_base + TWD_TIMER_INTSTAT)) {
                writel_relaxed(1, twd_base + TWD_TIMER_INTSTAT);
                return 1;
        }

        return 0;
}

static void twd_timer_stop(void)
{
        struct clock_event_device *clk = raw_cpu_ptr(twd_evt);

        twd_shutdown(clk);
        disable_percpu_irq(clk->irq);
}

/*
 * Updates clockevent frequency when the cpu frequency changes.
 * Called on the cpu that is changing frequency with interrupts disabled.
 */
static void twd_update_frequency(void *new_rate)
{
        twd_timer_rate = *((unsigned long *) new_rate);

        clockevents_update_freq(raw_cpu_ptr(twd_evt), twd_timer_rate);
}

static int twd_rate_change(struct notifier_block *nb,
        unsigned long flags, void *data)
{
        struct clk_notifier_data *cnd = data;

        /*
         * The twd clock events must be reprogrammed to account for the new
         * frequency.  The timer is local to a cpu, so cross-call to the
         * changing cpu.
         */
        if (flags == POST_RATE_CHANGE)
                on_each_cpu(twd_update_frequency,
                                  (void *)&cnd->new_rate, 1);

        return NOTIFY_OK;
}

static struct notifier_block twd_clk_nb = {
        .notifier_call = twd_rate_change,
};

static int twd_clk_init(void)
{
        if (twd_evt && raw_cpu_ptr(twd_evt) && !IS_ERR(twd_clk))
                return clk_notifier_register(twd_clk, &twd_clk_nb);

        return 0;
}
core_initcall(twd_clk_init);

static void twd_calibrate_rate(void)
{
        unsigned long count;
        u64 waitjiffies;

        /*
         * If this is the first time round, we need to work out how fast
         * the timer ticks
         */
        if (twd_timer_rate == 0) {
                pr_info("Calibrating local timer... ");

                /* Wait for a tick to start */
                waitjiffies = get_jiffies_64() + 1;

                while (get_jiffies_64() < waitjiffies)
                        udelay(10);

                /* OK, now the tick has started, let's get the timer going */
                waitjiffies += 5;

                                 /* enable, no interrupt or reload */
                writel_relaxed(0x1, twd_base + TWD_TIMER_CONTROL);

                                 /* maximum value */
                writel_relaxed(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);

                while (get_jiffies_64() < waitjiffies)
                        udelay(10);

                count = readl_relaxed(twd_base + TWD_TIMER_COUNTER);

                twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);

                pr_cont("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
                        (twd_timer_rate / 10000) % 100);
        }
}

static irqreturn_t twd_handler(int irq, void *dev_id)
{
        struct clock_event_device *evt = dev_id;

        if (twd_timer_ack()) {
                evt->event_handler(evt);
                return IRQ_HANDLED;
        }

        return IRQ_NONE;
}

static void twd_get_clock(struct device_node *np)
{
        int err;

        if (np)
                twd_clk = of_clk_get(np, 0);
        else
                twd_clk = clk_get_sys("smp_twd", NULL);

        if (IS_ERR(twd_clk)) {
                pr_err("smp_twd: clock not found %d\n", (int) PTR_ERR(twd_clk));
                return;
        }

        err = clk_prepare_enable(twd_clk);
        if (err) {
                pr_err("smp_twd: clock failed to prepare+enable: %d\n", err);
                clk_put(twd_clk);
                return;
        }

        twd_timer_rate = clk_get_rate(twd_clk);
}

/*
 * Setup the local clock events for a CPU.
 */
static void twd_timer_setup(void)
{
        struct clock_event_device *clk = raw_cpu_ptr(twd_evt);
        int cpu = smp_processor_id();

        /*
         * If the basic setup for this CPU has been done before don't
         * bother with the below.
         */
        if (per_cpu(percpu_setup_called, cpu)) {
                writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);
                clockevents_register_device(clk);
                enable_percpu_irq(clk->irq, 0);
                return;
        }
        per_cpu(percpu_setup_called, cpu) = true;

        twd_calibrate_rate();

        /*
         * The following is done once per CPU the first time .setup() is
         * called.
         */
        writel_relaxed(0, twd_base + TWD_TIMER_CONTROL);

        clk->name = "local_timer";
        clk->features = twd_features;
        clk->rating = 350;
        clk->set_state_shutdown = twd_shutdown;
        clk->set_state_periodic = twd_set_periodic;
        clk->set_state_oneshot = twd_set_oneshot;
        clk->tick_resume = twd_shutdown;
        clk->set_next_event = twd_set_next_event;
        clk->irq = twd_ppi;
        clk->cpumask = cpumask_of(cpu);

        clockevents_config_and_register(clk, twd_timer_rate,
                                        0xf, 0xffffffff);
        enable_percpu_irq(clk->irq, 0);
}

static int twd_timer_starting_cpu(unsigned int cpu)
{
        twd_timer_setup();
        return 0;
}

static int twd_timer_dying_cpu(unsigned int cpu)
{
        twd_timer_stop();
        return 0;
}

static int __init twd_local_timer_common_register(struct device_node *np)
{
        int err;

        twd_evt = alloc_percpu(struct clock_event_device);
        if (!twd_evt) {
                err = -ENOMEM;
                goto out_free;
        }

        err = request_percpu_irq(twd_ppi, twd_handler, "twd", twd_evt);
        if (err) {
                pr_err("twd: can't register interrupt %d (%d)\n", twd_ppi, err);
                goto out_free;
        }

        cpuhp_setup_state_nocalls(CPUHP_AP_ARM_TWD_STARTING,
                                  "arm/timer/twd:starting",
                                  twd_timer_starting_cpu, twd_timer_dying_cpu);

        twd_get_clock(np);
        if (!of_property_read_bool(np, "always-on"))
                twd_features |= CLOCK_EVT_FEAT_C3STOP;

        /*
         * Immediately configure the timer on the boot CPU, unless we need
         * jiffies to be incrementing to calibrate the rate in which case
         * setup the timer in late_time_init.
         */
        if (twd_timer_rate)
                twd_timer_setup();
        else
                late_time_init = twd_timer_setup;

        return 0;

out_free:
        iounmap(twd_base);
        twd_base = NULL;
        free_percpu(twd_evt);

        return err;
}

static int __init twd_local_timer_of_register(struct device_node *np)
{
        int err;

        twd_ppi = irq_of_parse_and_map(np, 0);
        if (!twd_ppi) {
                err = -EINVAL;
                goto out;
        }

        twd_base = of_iomap(np, 0);
        if (!twd_base) {
                err = -ENOMEM;
                goto out;
        }

        err = twd_local_timer_common_register(np);

out:
        WARN(err, "twd_local_timer_of_register failed (%d)\n", err);
        return err;
}
TIMER_OF_DECLARE(arm_twd_a9, "arm,cortex-a9-twd-timer", twd_local_timer_of_register);
TIMER_OF_DECLARE(arm_twd_a5, "arm,cortex-a5-twd-timer", twd_local_timer_of_register);
TIMER_OF_DECLARE(arm_twd_11mp, "arm,arm11mp-twd-timer", twd_local_timer_of_register);