// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright 2012 Simon Arlott
 */

#include <linux/bitops.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/interrupt.h>
#include <linux/irqreturn.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/sched_clock.h>

#include <asm/irq.h>

#define REG_CONTROL     0x00
#define REG_COUNTER_LO  0x04
#define REG_COUNTER_HI  0x08
#define REG_COMPARE(n)  (0x0c + (n) * 4)
#define MAX_TIMER       3
#define DEFAULT_TIMER   3

struct bcm2835_timer {
        void __iomem *control;
        void __iomem *compare;
        int match_mask;
        struct clock_event_device evt;
};

static void __iomem *system_clock __read_mostly;

static u64 notrace bcm2835_sched_read(void)
{
        return readl_relaxed(system_clock);
}

static int bcm2835_time_set_next_event(unsigned long event,
        struct clock_event_device *evt_dev)
{
        struct bcm2835_timer *timer = container_of(evt_dev,
                struct bcm2835_timer, evt);
        writel_relaxed(readl_relaxed(system_clock) + event,
                timer->compare);
        return 0;
}

static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
{
        struct bcm2835_timer *timer = dev_id;
        void (*event_handler)(struct clock_event_device *);
        if (readl_relaxed(timer->control) & timer->match_mask) {
                writel_relaxed(timer->match_mask, timer->control);

                event_handler = READ_ONCE(timer->evt.event_handler);
                if (event_handler)
                        event_handler(&timer->evt);
                return IRQ_HANDLED;
        } else {
                return IRQ_NONE;
        }
}

static int __init bcm2835_timer_init(struct device_node *node)
{
        void __iomem *base;
        u32 freq;
        int irq, ret;
        struct bcm2835_timer *timer;

        base = of_iomap(node, 0);
        if (!base) {
                pr_err("Can't remap registers\n");
                return -ENXIO;
        }

        ret = of_property_read_u32(node, "clock-frequency", &freq);
        if (ret) {
                pr_err("Can't read clock-frequency\n");
                goto err_iounmap;
        }

        system_clock = base + REG_COUNTER_LO;
        sched_clock_register(bcm2835_sched_read, 32, freq);

        clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
                freq, 300, 32, clocksource_mmio_readl_up);

        irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
        if (irq <= 0) {
                pr_err("Can't parse IRQ\n");
                ret = -EINVAL;
                goto err_iounmap;
        }

        timer = kzalloc_obj(*timer);
        if (!timer) {
                ret = -ENOMEM;
                goto err_iounmap;
        }

        timer->control = base + REG_CONTROL;
        timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
        timer->match_mask = BIT(DEFAULT_TIMER);
        timer->evt.name = node->name;
        timer->evt.rating = 300;
        timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
        timer->evt.set_next_event = bcm2835_time_set_next_event;
        timer->evt.cpumask = cpumask_of(0);

        ret = request_irq(irq, bcm2835_time_interrupt, IRQF_TIMER | IRQF_SHARED,
                          node->name, timer);
        if (ret) {
                pr_err("Can't set up timer IRQ\n");
                goto err_timer_free;
        }

        clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);

        pr_info("bcm2835: system timer (irq = %d)\n", irq);

        return 0;

err_timer_free:
        kfree(timer);

err_iounmap:
        iounmap(base);
        return ret;
}
TIMER_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
                        bcm2835_timer_init);