// SPDX-License-Identifier: GPL-2.0-only
/*
 * Ralink RT2880 timer
 * Author: John Crispin
 *
 * Copyright (C) 2013 John Crispin <john@phrozen.org>
*/

#include <linux/bits.h>
#include <linux/clk.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/mod_devicetable.h>
#include <linux/platform_device.h>
#include <linux/timer.h>
#include <linux/types.h>

#include <asm/mach-ralink/ralink_regs.h>

#define TIMER_REG_TMRSTAT               0x00
#define TIMER_REG_TMR0LOAD              0x10
#define TIMER_REG_TMR0CTL               0x18

#define TMRSTAT_TMR0INT                 BIT(0)

#define TMR0CTL_ENABLE                  BIT(7)
#define TMR0CTL_MODE_PERIODIC           BIT(4)
#define TMR0CTL_PRESCALER               1
#define TMR0CTL_PRESCALE_VAL            (0xf - TMR0CTL_PRESCALER)
#define TMR0CTL_PRESCALE_DIV            (65536 / BIT(TMR0CTL_PRESCALER))

struct rt_timer {
        struct device   *dev;
        void __iomem    *membase;
        int             irq;
        unsigned long   timer_freq;
        unsigned long   timer_div;
};

static inline void rt_timer_w32(struct rt_timer *rt, u8 reg, u32 val)
{
        __raw_writel(val, rt->membase + reg);
}

static inline u32 rt_timer_r32(struct rt_timer *rt, u8 reg)
{
        return __raw_readl(rt->membase + reg);
}

static irqreturn_t rt_timer_irq(int irq, void *_rt)
{
        struct rt_timer *rt =  (struct rt_timer *) _rt;

        rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
        rt_timer_w32(rt, TIMER_REG_TMRSTAT, TMRSTAT_TMR0INT);

        return IRQ_HANDLED;
}


static int rt_timer_request(struct rt_timer *rt)
{
        int err = request_irq(rt->irq, rt_timer_irq, 0,
                                                dev_name(rt->dev), rt);
        if (err) {
                dev_err(rt->dev, "failed to request irq\n");
        } else {
                u32 t = TMR0CTL_MODE_PERIODIC | TMR0CTL_PRESCALE_VAL;
                rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
        }
        return err;
}

static int rt_timer_config(struct rt_timer *rt, unsigned long divisor)
{
        if (rt->timer_freq < divisor)
                rt->timer_div = rt->timer_freq;
        else
                rt->timer_div = divisor;

        rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);

        return 0;
}

static int rt_timer_enable(struct rt_timer *rt)
{
        u32 t;

        rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);

        t = rt_timer_r32(rt, TIMER_REG_TMR0CTL);
        t |= TMR0CTL_ENABLE;
        rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);

        return 0;
}

static int rt_timer_probe(struct platform_device *pdev)
{
        struct rt_timer *rt;
        struct clk *clk;

        rt = devm_kzalloc(&pdev->dev, sizeof(*rt), GFP_KERNEL);
        if (!rt) {
                dev_err(&pdev->dev, "failed to allocate memory\n");
                return -ENOMEM;
        }

        rt->irq = platform_get_irq(pdev, 0);
        if (rt->irq < 0)
                return rt->irq;

        rt->membase = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
        if (IS_ERR(rt->membase))
                return PTR_ERR(rt->membase);

        clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(clk)) {
                dev_err(&pdev->dev, "failed get clock rate\n");
                return PTR_ERR(clk);
        }

        rt->timer_freq = clk_get_rate(clk) / TMR0CTL_PRESCALE_DIV;
        if (!rt->timer_freq)
                return -EINVAL;

        rt->dev = &pdev->dev;
        platform_set_drvdata(pdev, rt);

        rt_timer_request(rt);
        rt_timer_config(rt, 2);
        rt_timer_enable(rt);

        dev_info(&pdev->dev, "maximum frequency is %luHz\n", rt->timer_freq);

        return 0;
}

static const struct of_device_id rt_timer_match[] = {
        { .compatible = "ralink,rt2880-timer" },
        {},
};

static struct platform_driver rt_timer_driver = {
        .probe = rt_timer_probe,
        .driver = {
                .name                   = "rt-timer",
                .of_match_table         = rt_timer_match,
                .suppress_bind_attrs    = true,
        },
};
builtin_platform_driver(rt_timer_driver);