// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Support code for virtual Ranchu board for MIPS.
 *
 * Author: Miodrag Dinic <miodrag.dinic@mips.com>
 */

#include <linux/of_address.h>
#include <linux/types.h>

#include <asm/machine.h>
#include <asm/mipsregs.h>
#include <asm/time.h>

#define GOLDFISH_TIMER_LOW              0x00
#define GOLDFISH_TIMER_HIGH             0x04

static __init u64 read_rtc_time(void __iomem *base)
{
        u32 time_low;
        u32 time_high;

        /*
         * Reading the low address latches the high value
         * as well so there is no fear that we may read
         * inaccurate high value.
         */
        time_low = readl(base + GOLDFISH_TIMER_LOW);
        time_high = readl(base + GOLDFISH_TIMER_HIGH);

        return ((u64)time_high << 32) | time_low;
}

static __init unsigned int ranchu_measure_hpt_freq(void)
{
        u64 rtc_start, rtc_current, rtc_delta;
        unsigned int start, count;
        struct device_node *np;
        void __iomem *rtc_base;

        np = of_find_compatible_node(NULL, NULL, "google,goldfish-rtc");
        if (!np)
                panic("%s(): Failed to find 'google,goldfish-rtc' dt node!",
                      __func__);

        rtc_base = of_iomap(np, 0);
        of_node_put(np);
        if (!rtc_base)
                panic("%s(): Failed to ioremap Goldfish RTC base!", __func__);

        /*
         * Poll the nanosecond resolution RTC for one
         * second to calibrate the CPU frequency.
         */
        rtc_start = read_rtc_time(rtc_base);
        start = read_c0_count();

        do {
                rtc_current = read_rtc_time(rtc_base);
                rtc_delta = rtc_current - rtc_start;
        } while (rtc_delta < NSEC_PER_SEC);

        count = read_c0_count() - start;

        /*
         * Make sure the frequency will be a round number.
         * Without this correction, the returned value may vary
         * between subsequent emulation executions.
         *
         * TODO: Set this value using device tree.
         */
        count += 5000;
        count -= count % 10000;

        iounmap(rtc_base);

        return count;
}

static const struct of_device_id ranchu_of_match[] __initconst = {
        {
                .compatible = "mti,ranchu",
        },
        {}
};

MIPS_MACHINE(ranchu) = {
        .matches = ranchu_of_match,
        .measure_hpt_freq = ranchu_measure_hpt_freq,
};