// SPDX-License-Identifier: GPL-2.0
/*
 * Ralink System Tick Counter driver present on RT3352 and MT7620 SoCs.
 *
 * Copyright (C) 2013 by John Crispin <john@phrozen.org>
 */

#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/interrupt.h>
#include <linux/reset.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/of_address.h>

#define SYSTICK_FREQ            (50 * 1000)

#define SYSTICK_CONFIG          0x00
#define SYSTICK_COMPARE         0x04
#define SYSTICK_COUNT           0x08

/* route systick irq to mips irq 7 instead of the r4k-timer */
#define CFG_EXT_STK_EN          0x2
/* enable the counter */
#define CFG_CNT_EN              0x1

struct systick_device {
        void __iomem *membase;
        struct clock_event_device dev;
        int irq_requested;
        int freq_scale;
};

static int systick_set_oneshot(struct clock_event_device *evt);
static int systick_shutdown(struct clock_event_device *evt);

static int systick_next_event(unsigned long delta,
                              struct clock_event_device *evt)
{
        struct systick_device *sdev;
        u32 count;

        sdev = container_of(evt, struct systick_device, dev);
        count = ioread32(sdev->membase + SYSTICK_COUNT);
        count = (count + delta) % SYSTICK_FREQ;
        iowrite32(count, sdev->membase + SYSTICK_COMPARE);

        return 0;
}

static void systick_event_handler(struct clock_event_device *dev)
{
        /* noting to do here */
}

static irqreturn_t systick_interrupt(int irq, void *dev_id)
{
        struct clock_event_device *dev = (struct clock_event_device *)dev_id;

        dev->event_handler(dev);

        return IRQ_HANDLED;
}

static struct systick_device systick = {
        .dev = {
                /*
                 * cevt-r4k uses 300, make sure systick
                 * gets used if available
                 */
                .rating                 = 310,
                .features               = CLOCK_EVT_FEAT_ONESHOT,
                .set_next_event         = systick_next_event,
                .set_state_shutdown     = systick_shutdown,
                .set_state_oneshot      = systick_set_oneshot,
                .event_handler          = systick_event_handler,
        },
};

static int systick_shutdown(struct clock_event_device *evt)
{
        struct systick_device *sdev;

        sdev = container_of(evt, struct systick_device, dev);

        if (sdev->irq_requested)
                free_irq(systick.dev.irq, &systick.dev);
        sdev->irq_requested = 0;
        iowrite32(0, systick.membase + SYSTICK_CONFIG);

        return 0;
}

static int systick_set_oneshot(struct clock_event_device *evt)
{
        const char *name = systick.dev.name;
        struct systick_device *sdev;
        int irq = systick.dev.irq;

        sdev = container_of(evt, struct systick_device, dev);

        if (!sdev->irq_requested) {
                if (request_irq(irq, systick_interrupt,
                                IRQF_PERCPU | IRQF_TIMER, name, &systick.dev))
                        pr_err("Failed to request irq %d (%s)\n", irq, name);
        }
        sdev->irq_requested = 1;
        iowrite32(CFG_EXT_STK_EN | CFG_CNT_EN,
                  systick.membase + SYSTICK_CONFIG);

        return 0;
}

static int __init ralink_systick_init(struct device_node *np)
{
        int ret;

        systick.membase = of_iomap(np, 0);
        if (!systick.membase)
                return -ENXIO;

        systick.dev.name = np->name;
        clockevents_calc_mult_shift(&systick.dev, SYSTICK_FREQ, 60);
        systick.dev.max_delta_ns = clockevent_delta2ns(0x7fff, &systick.dev);
        systick.dev.max_delta_ticks = 0x7fff;
        systick.dev.min_delta_ns = clockevent_delta2ns(0x3, &systick.dev);
        systick.dev.min_delta_ticks = 0x3;
        systick.dev.irq = irq_of_parse_and_map(np, 0);
        if (!systick.dev.irq) {
                pr_err("%pOFn: request_irq failed", np);
                ret = -EINVAL;
                goto err_iounmap;
        }

        ret = clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name,
                                    SYSTICK_FREQ, 301, 16,
                                    clocksource_mmio_readl_up);
        if (ret)
                goto err_free_irq;

        clockevents_register_device(&systick.dev);

        pr_info("%pOFn: running - mult: %d, shift: %d\n",
                        np, systick.dev.mult, systick.dev.shift);

        return 0;

err_free_irq:
        irq_dispose_mapping(systick.dev.irq);
err_iounmap:
        iounmap(systick.membase);
        return ret;
}

TIMER_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init);