// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2014 Oleksij Rempel <linux@rempel-privat.de>
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/clk.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/bitops.h>

#define DRIVER_NAME     "asm9260-timer"

/*
 * this device provide 4 offsets for each register:
 * 0x0 - plain read write mode
 * 0x4 - set mode, OR logic.
 * 0x8 - clr mode, XOR logic.
 * 0xc - togle mode.
 */
#define SET_REG 4
#define CLR_REG 8

#define HW_IR           0x0000 /* RW. Interrupt */
#define BM_IR_CR0       BIT(4)
#define BM_IR_MR3       BIT(3)
#define BM_IR_MR2       BIT(2)
#define BM_IR_MR1       BIT(1)
#define BM_IR_MR0       BIT(0)

#define HW_TCR          0x0010 /* RW. Timer controller */
/* BM_C*_RST
 * Timer Counter and the Prescale Counter are synchronously reset on the
 * next positive edge of PCLK. The counters remain reset until TCR[1] is
 * returned to zero. */
#define BM_C3_RST       BIT(7)
#define BM_C2_RST       BIT(6)
#define BM_C1_RST       BIT(5)
#define BM_C0_RST       BIT(4)
/* BM_C*_EN
 * 1 - Timer Counter and Prescale Counter are enabled for counting
 * 0 - counters are disabled */
#define BM_C3_EN        BIT(3)
#define BM_C2_EN        BIT(2)
#define BM_C1_EN        BIT(1)
#define BM_C0_EN        BIT(0)

#define HW_DIR          0x0020 /* RW. Direction? */
/* 00 - count up
 * 01 - count down
 * 10 - ?? 2^n/2 */
#define BM_DIR_COUNT_UP         0
#define BM_DIR_COUNT_DOWN       1
#define BM_DIR0_SHIFT   0
#define BM_DIR1_SHIFT   4
#define BM_DIR2_SHIFT   8
#define BM_DIR3_SHIFT   12
#define BM_DIR_DEFAULT          (BM_DIR_COUNT_UP << BM_DIR0_SHIFT | \
                                 BM_DIR_COUNT_UP << BM_DIR1_SHIFT | \
                                 BM_DIR_COUNT_UP << BM_DIR2_SHIFT | \
                                 BM_DIR_COUNT_UP << BM_DIR3_SHIFT)

#define HW_TC0          0x0030 /* RO. Timer counter 0 */
/* HW_TC*. Timer counter owerflow (0xffff.ffff to 0x0000.0000) do not generate
 * interrupt. This registers can be used to detect overflow */
#define HW_TC1          0x0040
#define HW_TC2          0x0050
#define HW_TC3          0x0060

#define HW_PR           0x0070 /* RW. prescaler */
#define BM_PR_DISABLE   0
#define HW_PC           0x0080 /* RO. Prescaler counter */
#define HW_MCR          0x0090 /* RW. Match control */
/* enable interrupt on match */
#define BM_MCR_INT_EN(n)        (1 << (n * 3 + 0))
/* enable TC reset on match */
#define BM_MCR_RES_EN(n)        (1 << (n * 3 + 1))
/* enable stop TC on match */
#define BM_MCR_STOP_EN(n)       (1 << (n * 3 + 2))

#define HW_MR0          0x00a0 /* RW. Match reg */
#define HW_MR1          0x00b0
#define HW_MR2          0x00C0
#define HW_MR3          0x00D0

#define HW_CTCR         0x0180 /* Counter control */
#define BM_CTCR0_SHIFT  0
#define BM_CTCR1_SHIFT  2
#define BM_CTCR2_SHIFT  4
#define BM_CTCR3_SHIFT  6
#define BM_CTCR_TM      0       /* Timer mode. Every rising PCLK edge. */
#define BM_CTCR_DEFAULT (BM_CTCR_TM << BM_CTCR0_SHIFT | \
                         BM_CTCR_TM << BM_CTCR1_SHIFT | \
                         BM_CTCR_TM << BM_CTCR2_SHIFT | \
                         BM_CTCR_TM << BM_CTCR3_SHIFT)

static struct asm9260_timer_priv {
        void __iomem *base;
        unsigned long ticks_per_jiffy;
} priv;

static int asm9260_timer_set_next_event(unsigned long delta,
                                         struct clock_event_device *evt)
{
        /* configure match count for TC0 */
        writel_relaxed(delta, priv.base + HW_MR0);
        /* enable TC0 */
        writel_relaxed(BM_C0_EN, priv.base + HW_TCR + SET_REG);
        return 0;
}

static inline void __asm9260_timer_shutdown(struct clock_event_device *evt)
{
        /* stop timer0 */
        writel_relaxed(BM_C0_EN, priv.base + HW_TCR + CLR_REG);
}

static int asm9260_timer_shutdown(struct clock_event_device *evt)
{
        __asm9260_timer_shutdown(evt);
        return 0;
}

static int asm9260_timer_set_oneshot(struct clock_event_device *evt)
{
        __asm9260_timer_shutdown(evt);

        /* enable reset and stop on match */
        writel_relaxed(BM_MCR_RES_EN(0) | BM_MCR_STOP_EN(0),
                       priv.base + HW_MCR + SET_REG);
        return 0;
}

static int asm9260_timer_set_periodic(struct clock_event_device *evt)
{
        __asm9260_timer_shutdown(evt);

        /* disable reset and stop on match */
        writel_relaxed(BM_MCR_RES_EN(0) | BM_MCR_STOP_EN(0),
                       priv.base + HW_MCR + CLR_REG);
        /* configure match count for TC0 */
        writel_relaxed(priv.ticks_per_jiffy, priv.base + HW_MR0);
        /* enable TC0 */
        writel_relaxed(BM_C0_EN, priv.base + HW_TCR + SET_REG);
        return 0;
}

static struct clock_event_device event_dev = {
        .name                   = DRIVER_NAME,
        .rating                 = 200,
        .features               = CLOCK_EVT_FEAT_PERIODIC |
                                  CLOCK_EVT_FEAT_ONESHOT,
        .set_next_event         = asm9260_timer_set_next_event,
        .set_state_shutdown     = asm9260_timer_shutdown,
        .set_state_periodic     = asm9260_timer_set_periodic,
        .set_state_oneshot      = asm9260_timer_set_oneshot,
        .tick_resume            = asm9260_timer_shutdown,
};

static irqreturn_t asm9260_timer_interrupt(int irq, void *dev_id)
{
        struct clock_event_device *evt = dev_id;

        evt->event_handler(evt);

        writel_relaxed(BM_IR_MR0, priv.base + HW_IR);

        return IRQ_HANDLED;
}

/*
 * ---------------------------------------------------------------------------
 * Timer initialization
 * ---------------------------------------------------------------------------
 */
static int __init asm9260_timer_init(struct device_node *np)
{
        int irq;
        struct clk *clk;
        int ret;
        unsigned long rate;

        priv.base = of_io_request_and_map(np, 0, np->name);
        if (IS_ERR(priv.base)) {
                pr_err("%pOFn: unable to map resource\n", np);
                return PTR_ERR(priv.base);
        }

        clk = of_clk_get(np, 0);
        if (IS_ERR(clk)) {
                pr_err("Failed to get clk!\n");
                return PTR_ERR(clk);
        }

        ret = clk_prepare_enable(clk);
        if (ret) {
                pr_err("Failed to enable clk!\n");
                return ret;
        }

        irq = irq_of_parse_and_map(np, 0);
        ret = request_irq(irq, asm9260_timer_interrupt, IRQF_TIMER,
                        DRIVER_NAME, &event_dev);
        if (ret) {
                pr_err("Failed to setup irq!\n");
                clk_disable_unprepare(clk);
                return ret;
        }

        /* set all timers for count-up */
        writel_relaxed(BM_DIR_DEFAULT, priv.base + HW_DIR);
        /* disable divider */
        writel_relaxed(BM_PR_DISABLE, priv.base + HW_PR);
        /* make sure all timers use every rising PCLK edge. */
        writel_relaxed(BM_CTCR_DEFAULT, priv.base + HW_CTCR);
        /* enable interrupt for TC0 and clean setting for all other lines */
        writel_relaxed(BM_MCR_INT_EN(0) , priv.base + HW_MCR);

        rate = clk_get_rate(clk);
        clocksource_mmio_init(priv.base + HW_TC1, DRIVER_NAME, rate,
                        200, 32, clocksource_mmio_readl_up);

        /* Seems like we can't use counter without match register even if
         * actions for MR are disabled. So, set MR to max value. */
        writel_relaxed(0xffffffff, priv.base + HW_MR1);
        /* enable TC1 */
        writel_relaxed(BM_C1_EN, priv.base + HW_TCR + SET_REG);

        priv.ticks_per_jiffy = DIV_ROUND_CLOSEST(rate, HZ);
        event_dev.cpumask = cpumask_of(0);
        clockevents_config_and_register(&event_dev, rate, 0x2c00, 0xfffffffe);

        return 0;
}
TIMER_OF_DECLARE(asm9260_timer, "alphascale,asm9260-timer",
                asm9260_timer_init);