/*
 * SuperH Timer Support - CMT
 *
 *  Copyright (C) 2008 Magnus Damm
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/clk.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_domain.h>
#include <linux/pm_runtime.h>
#include <linux/sh_timer.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

struct sh_cmt_device;

/*
 * The CMT comes in 5 different identified flavours, depending not only on the
 * SoC but also on the particular instance. The following table lists the main
 * characteristics of those flavours.
 *
 *                      16B     32B     32B-F   48B     48B-2
 * -----------------------------------------------------------------------------
 * Channels             2       1/4     1       6       2/8
 * Control Width        16      16      16      16      32
 * Counter Width        16      32      32      32/48   32/48
 * Shared Start/Stop    Y       Y       Y       Y       N
 *
 * The 48-bit gen2 version has a per-channel start/stop register located in the
 * channel registers block. All other versions have a shared start/stop register
 * located in the global space.
 *
 * Channels are indexed from 0 to N-1 in the documentation. The channel index
 * infers the start/stop bit position in the control register and the channel
 * registers block address. Some CMT instances have a subset of channels
 * available, in which case the index in the documentation doesn't match the
 * "real" index as implemented in hardware. This is for instance the case with
 * CMT0 on r8a7740, which is a 32-bit variant with a single channel numbered 0
 * in the documentation but using start/stop bit 5 and having its registers
 * block at 0x60.
 *
 * Similarly CMT0 on r8a73a4, r8a7790 and r8a7791, while implementing 32-bit
 * channels only, is a 48-bit gen2 CMT with the 48-bit channels unavailable.
 */

enum sh_cmt_model {
        SH_CMT_16BIT,
        SH_CMT_32BIT,
        SH_CMT_32BIT_FAST,
        SH_CMT_48BIT,
        SH_CMT_48BIT_GEN2,
};

struct sh_cmt_info {
        enum sh_cmt_model model;

        unsigned long width; /* 16 or 32 bit version of hardware block */
        unsigned long overflow_bit;
        unsigned long clear_bits;

        /* callbacks for CMSTR and CMCSR access */
        unsigned long (*read_control)(void __iomem *base, unsigned long offs);
        void (*write_control)(void __iomem *base, unsigned long offs,
                              unsigned long value);

        /* callbacks for CMCNT and CMCOR access */
        unsigned long (*read_count)(void __iomem *base, unsigned long offs);
        void (*write_count)(void __iomem *base, unsigned long offs,
                            unsigned long value);
};

struct sh_cmt_channel {
        struct sh_cmt_device *cmt;

        unsigned int index;     /* Index in the documentation */
        unsigned int hwidx;     /* Real hardware index */

        void __iomem *iostart;
        void __iomem *ioctrl;

        unsigned int timer_bit;
        unsigned long flags;
        unsigned long match_value;
        unsigned long next_match_value;
        unsigned long max_match_value;
        unsigned long rate;
        raw_spinlock_t lock;
        struct clock_event_device ced;
        struct clocksource cs;
        unsigned long total_cycles;
        bool cs_enabled;
};

struct sh_cmt_device {
        struct platform_device *pdev;

        const struct sh_cmt_info *info;

        void __iomem *mapbase;
        struct clk *clk;

        raw_spinlock_t lock; /* Protect the shared start/stop register */

        struct sh_cmt_channel *channels;
        unsigned int num_channels;
        unsigned int hw_channels;

        bool has_clockevent;
        bool has_clocksource;
};

#define SH_CMT16_CMCSR_CMF              (1 << 7)
#define SH_CMT16_CMCSR_CMIE             (1 << 6)
#define SH_CMT16_CMCSR_CKS8             (0 << 0)
#define SH_CMT16_CMCSR_CKS32            (1 << 0)
#define SH_CMT16_CMCSR_CKS128           (2 << 0)
#define SH_CMT16_CMCSR_CKS512           (3 << 0)
#define SH_CMT16_CMCSR_CKS_MASK         (3 << 0)

#define SH_CMT32_CMCSR_CMF              (1 << 15)
#define SH_CMT32_CMCSR_OVF              (1 << 14)
#define SH_CMT32_CMCSR_WRFLG            (1 << 13)
#define SH_CMT32_CMCSR_STTF             (1 << 12)
#define SH_CMT32_CMCSR_STPF             (1 << 11)
#define SH_CMT32_CMCSR_SSIE             (1 << 10)
#define SH_CMT32_CMCSR_CMS              (1 << 9)
#define SH_CMT32_CMCSR_CMM              (1 << 8)
#define SH_CMT32_CMCSR_CMTOUT_IE        (1 << 7)
#define SH_CMT32_CMCSR_CMR_NONE         (0 << 4)
#define SH_CMT32_CMCSR_CMR_DMA          (1 << 4)
#define SH_CMT32_CMCSR_CMR_IRQ          (2 << 4)
#define SH_CMT32_CMCSR_CMR_MASK         (3 << 4)
#define SH_CMT32_CMCSR_DBGIVD           (1 << 3)
#define SH_CMT32_CMCSR_CKS_RCLK8        (4 << 0)
#define SH_CMT32_CMCSR_CKS_RCLK32       (5 << 0)
#define SH_CMT32_CMCSR_CKS_RCLK128      (6 << 0)
#define SH_CMT32_CMCSR_CKS_RCLK1        (7 << 0)
#define SH_CMT32_CMCSR_CKS_MASK         (7 << 0)

static unsigned long sh_cmt_read16(void __iomem *base, unsigned long offs)
{
        return ioread16(base + (offs << 1));
}

static unsigned long sh_cmt_read32(void __iomem *base, unsigned long offs)
{
        return ioread32(base + (offs << 2));
}

static void sh_cmt_write16(void __iomem *base, unsigned long offs,
                           unsigned long value)
{
        iowrite16(value, base + (offs << 1));
}

static void sh_cmt_write32(void __iomem *base, unsigned long offs,
                           unsigned long value)
{
        iowrite32(value, base + (offs << 2));
}

static const struct sh_cmt_info sh_cmt_info[] = {
        [SH_CMT_16BIT] = {
                .model = SH_CMT_16BIT,
                .width = 16,
                .overflow_bit = SH_CMT16_CMCSR_CMF,
                .clear_bits = ~SH_CMT16_CMCSR_CMF,
                .read_control = sh_cmt_read16,
                .write_control = sh_cmt_write16,
                .read_count = sh_cmt_read16,
                .write_count = sh_cmt_write16,
        },
        [SH_CMT_32BIT] = {
                .model = SH_CMT_32BIT,
                .width = 32,
                .overflow_bit = SH_CMT32_CMCSR_CMF,
                .clear_bits = ~(SH_CMT32_CMCSR_CMF | SH_CMT32_CMCSR_OVF),
                .read_control = sh_cmt_read16,
                .write_control = sh_cmt_write16,
                .read_count = sh_cmt_read32,
                .write_count = sh_cmt_write32,
        },
        [SH_CMT_32BIT_FAST] = {
                .model = SH_CMT_32BIT_FAST,
                .width = 32,
                .overflow_bit = SH_CMT32_CMCSR_CMF,
                .clear_bits = ~(SH_CMT32_CMCSR_CMF | SH_CMT32_CMCSR_OVF),
                .read_control = sh_cmt_read16,
                .write_control = sh_cmt_write16,
                .read_count = sh_cmt_read32,
                .write_count = sh_cmt_write32,
        },
        [SH_CMT_48BIT] = {
                .model = SH_CMT_48BIT,
                .width = 32,
                .overflow_bit = SH_CMT32_CMCSR_CMF,
                .clear_bits = ~(SH_CMT32_CMCSR_CMF | SH_CMT32_CMCSR_OVF),
                .read_control = sh_cmt_read32,
                .write_control = sh_cmt_write32,
                .read_count = sh_cmt_read32,
                .write_count = sh_cmt_write32,
        },
        [SH_CMT_48BIT_GEN2] = {
                .model = SH_CMT_48BIT_GEN2,
                .width = 32,
                .overflow_bit = SH_CMT32_CMCSR_CMF,
                .clear_bits = ~(SH_CMT32_CMCSR_CMF | SH_CMT32_CMCSR_OVF),
                .read_control = sh_cmt_read32,
                .write_control = sh_cmt_write32,
                .read_count = sh_cmt_read32,
                .write_count = sh_cmt_write32,
        },
};

#define CMCSR 0 /* channel register */
#define CMCNT 1 /* channel register */
#define CMCOR 2 /* channel register */

static inline unsigned long sh_cmt_read_cmstr(struct sh_cmt_channel *ch)
{
        if (ch->iostart)
                return ch->cmt->info->read_control(ch->iostart, 0);
        else
                return ch->cmt->info->read_control(ch->cmt->mapbase, 0);
}

static inline void sh_cmt_write_cmstr(struct sh_cmt_channel *ch,
                                      unsigned long value)
{
        if (ch->iostart)
                ch->cmt->info->write_control(ch->iostart, 0, value);
        else
                ch->cmt->info->write_control(ch->cmt->mapbase, 0, value);
}

static inline unsigned long sh_cmt_read_cmcsr(struct sh_cmt_channel *ch)
{
        return ch->cmt->info->read_control(ch->ioctrl, CMCSR);
}

static inline void sh_cmt_write_cmcsr(struct sh_cmt_channel *ch,
                                      unsigned long value)
{
        ch->cmt->info->write_control(ch->ioctrl, CMCSR, value);
}

static inline unsigned long sh_cmt_read_cmcnt(struct sh_cmt_channel *ch)
{
        return ch->cmt->info->read_count(ch->ioctrl, CMCNT);
}

static inline void sh_cmt_write_cmcnt(struct sh_cmt_channel *ch,
                                      unsigned long value)
{
        ch->cmt->info->write_count(ch->ioctrl, CMCNT, value);
}

static inline void sh_cmt_write_cmcor(struct sh_cmt_channel *ch,
                                      unsigned long value)
{
        ch->cmt->info->write_count(ch->ioctrl, CMCOR, value);
}

static unsigned long sh_cmt_get_counter(struct sh_cmt_channel *ch,
                                        int *has_wrapped)
{
        unsigned long v1, v2, v3;
        int o1, o2;

        o1 = sh_cmt_read_cmcsr(ch) & ch->cmt->info->overflow_bit;

        /* Make sure the timer value is stable. Stolen from acpi_pm.c */
        do {
                o2 = o1;
                v1 = sh_cmt_read_cmcnt(ch);
                v2 = sh_cmt_read_cmcnt(ch);
                v3 = sh_cmt_read_cmcnt(ch);
                o1 = sh_cmt_read_cmcsr(ch) & ch->cmt->info->overflow_bit;
        } while (unlikely((o1 != o2) || (v1 > v2 && v1 < v3)
                          || (v2 > v3 && v2 < v1) || (v3 > v1 && v3 < v2)));

        *has_wrapped = o1;
        return v2;
}

static void sh_cmt_start_stop_ch(struct sh_cmt_channel *ch, int start)
{
        unsigned long flags, value;

        /* start stop register shared by multiple timer channels */
        raw_spin_lock_irqsave(&ch->cmt->lock, flags);
        value = sh_cmt_read_cmstr(ch);

        if (start)
                value |= 1 << ch->timer_bit;
        else
                value &= ~(1 << ch->timer_bit);

        sh_cmt_write_cmstr(ch, value);
        raw_spin_unlock_irqrestore(&ch->cmt->lock, flags);
}

static int sh_cmt_enable(struct sh_cmt_channel *ch, unsigned long *rate)
{
        int k, ret;

        pm_runtime_get_sync(&ch->cmt->pdev->dev);
        dev_pm_syscore_device(&ch->cmt->pdev->dev, true);

        /* enable clock */
        ret = clk_enable(ch->cmt->clk);
        if (ret) {
                dev_err(&ch->cmt->pdev->dev, "ch%u: cannot enable clock\n",
                        ch->index);
                goto err0;
        }

        /* make sure channel is disabled */
        sh_cmt_start_stop_ch(ch, 0);

        /* configure channel, periodic mode and maximum timeout */
        if (ch->cmt->info->width == 16) {
                *rate = clk_get_rate(ch->cmt->clk) / 512;
                sh_cmt_write_cmcsr(ch, SH_CMT16_CMCSR_CMIE |
                                   SH_CMT16_CMCSR_CKS512);
        } else {
                *rate = clk_get_rate(ch->cmt->clk) / 8;
                sh_cmt_write_cmcsr(ch, SH_CMT32_CMCSR_CMM |
                                   SH_CMT32_CMCSR_CMTOUT_IE |
                                   SH_CMT32_CMCSR_CMR_IRQ |
                                   SH_CMT32_CMCSR_CKS_RCLK8);
        }

        sh_cmt_write_cmcor(ch, 0xffffffff);
        sh_cmt_write_cmcnt(ch, 0);

        /*
         * According to the sh73a0 user's manual, as CMCNT can be operated
         * only by the RCLK (Pseudo 32 KHz), there's one restriction on
         * modifying CMCNT register; two RCLK cycles are necessary before
         * this register is either read or any modification of the value
         * it holds is reflected in the LSI's actual operation.
         *
         * While at it, we're supposed to clear out the CMCNT as of this
         * moment, so make sure it's processed properly here.  This will
         * take RCLKx2 at maximum.
         */
        for (k = 0; k < 100; k++) {
                if (!sh_cmt_read_cmcnt(ch))
                        break;
                udelay(1);
        }

        if (sh_cmt_read_cmcnt(ch)) {
                dev_err(&ch->cmt->pdev->dev, "ch%u: cannot clear CMCNT\n",
                        ch->index);
                ret = -ETIMEDOUT;
                goto err1;
        }

        /* enable channel */
        sh_cmt_start_stop_ch(ch, 1);
        return 0;
 err1:
        /* stop clock */
        clk_disable(ch->cmt->clk);

 err0:
        return ret;
}

static void sh_cmt_disable(struct sh_cmt_channel *ch)
{
        /* disable channel */
        sh_cmt_start_stop_ch(ch, 0);

        /* disable interrupts in CMT block */
        sh_cmt_write_cmcsr(ch, 0);

        /* stop clock */
        clk_disable(ch->cmt->clk);

        dev_pm_syscore_device(&ch->cmt->pdev->dev, false);
        pm_runtime_put(&ch->cmt->pdev->dev);
}

/* private flags */
#define FLAG_CLOCKEVENT (1 << 0)
#define FLAG_CLOCKSOURCE (1 << 1)
#define FLAG_REPROGRAM (1 << 2)
#define FLAG_SKIPEVENT (1 << 3)
#define FLAG_IRQCONTEXT (1 << 4)

static void sh_cmt_clock_event_program_verify(struct sh_cmt_channel *ch,
                                              int absolute)
{
        unsigned long new_match;
        unsigned long value = ch->next_match_value;
        unsigned long delay = 0;
        unsigned long now = 0;
        int has_wrapped;

        now = sh_cmt_get_counter(ch, &has_wrapped);
        ch->flags |= FLAG_REPROGRAM; /* force reprogram */

        if (has_wrapped) {
                /* we're competing with the interrupt handler.
                 *  -> let the interrupt handler reprogram the timer.
                 *  -> interrupt number two handles the event.
                 */
                ch->flags |= FLAG_SKIPEVENT;
                return;
        }

        if (absolute)
                now = 0;

        do {
                /* reprogram the timer hardware,
                 * but don't save the new match value yet.
                 */
                new_match = now + value + delay;
                if (new_match > ch->max_match_value)
                        new_match = ch->max_match_value;

                sh_cmt_write_cmcor(ch, new_match);

                now = sh_cmt_get_counter(ch, &has_wrapped);
                if (has_wrapped && (new_match > ch->match_value)) {
                        /* we are changing to a greater match value,
                         * so this wrap must be caused by the counter
                         * matching the old value.
                         * -> first interrupt reprograms the timer.
                         * -> interrupt number two handles the event.
                         */
                        ch->flags |= FLAG_SKIPEVENT;
                        break;
                }

                if (has_wrapped) {
                        /* we are changing to a smaller match value,
                         * so the wrap must be caused by the counter
                         * matching the new value.
                         * -> save programmed match value.
                         * -> let isr handle the event.
                         */
                        ch->match_value = new_match;
                        break;
                }

                /* be safe: verify hardware settings */
                if (now < new_match) {
                        /* timer value is below match value, all good.
                         * this makes sure we won't miss any match events.
                         * -> save programmed match value.
                         * -> let isr handle the event.
                         */
                        ch->match_value = new_match;
                        break;
                }

                /* the counter has reached a value greater
                 * than our new match value. and since the
                 * has_wrapped flag isn't set we must have
                 * programmed a too close event.
                 * -> increase delay and retry.
                 */
                if (delay)
                        delay <<= 1;
                else
                        delay = 1;

                if (!delay)
                        dev_warn(&ch->cmt->pdev->dev, "ch%u: too long delay\n",
                                 ch->index);

        } while (delay);
}

static void __sh_cmt_set_next(struct sh_cmt_channel *ch, unsigned long delta)
{
        if (delta > ch->max_match_value)
                dev_warn(&ch->cmt->pdev->dev, "ch%u: delta out of range\n",
                         ch->index);

        ch->next_match_value = delta;
        sh_cmt_clock_event_program_verify(ch, 0);
}

static void sh_cmt_set_next(struct sh_cmt_channel *ch, unsigned long delta)
{
        unsigned long flags;

        raw_spin_lock_irqsave(&ch->lock, flags);
        __sh_cmt_set_next(ch, delta);
        raw_spin_unlock_irqrestore(&ch->lock, flags);
}

static irqreturn_t sh_cmt_interrupt(int irq, void *dev_id)
{
        struct sh_cmt_channel *ch = dev_id;

        /* clear flags */
        sh_cmt_write_cmcsr(ch, sh_cmt_read_cmcsr(ch) &
                           ch->cmt->info->clear_bits);

        /* update clock source counter to begin with if enabled
         * the wrap flag should be cleared by the timer specific
         * isr before we end up here.
         */
        if (ch->flags & FLAG_CLOCKSOURCE)
                ch->total_cycles += ch->match_value + 1;

        if (!(ch->flags & FLAG_REPROGRAM))
                ch->next_match_value = ch->max_match_value;

        ch->flags |= FLAG_IRQCONTEXT;

        if (ch->flags & FLAG_CLOCKEVENT) {
                if (!(ch->flags & FLAG_SKIPEVENT)) {
                        if (ch->ced.mode == CLOCK_EVT_MODE_ONESHOT) {
                                ch->next_match_value = ch->max_match_value;
                                ch->flags |= FLAG_REPROGRAM;
                        }

                        ch->ced.event_handler(&ch->ced);
                }
        }

        ch->flags &= ~FLAG_SKIPEVENT;

        if (ch->flags & FLAG_REPROGRAM) {
                ch->flags &= ~FLAG_REPROGRAM;
                sh_cmt_clock_event_program_verify(ch, 1);

                if (ch->flags & FLAG_CLOCKEVENT)
                        if ((ch->ced.mode == CLOCK_EVT_MODE_SHUTDOWN)
                            || (ch->match_value == ch->next_match_value))
                                ch->flags &= ~FLAG_REPROGRAM;
        }

        ch->flags &= ~FLAG_IRQCONTEXT;

        return IRQ_HANDLED;
}

static int sh_cmt_start(struct sh_cmt_channel *ch, unsigned long flag)
{
        int ret = 0;
        unsigned long flags;

        raw_spin_lock_irqsave(&ch->lock, flags);

        if (!(ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE)))
                ret = sh_cmt_enable(ch, &ch->rate);

        if (ret)
                goto out;
        ch->flags |= flag;

        /* setup timeout if no clockevent */
        if ((flag == FLAG_CLOCKSOURCE) && (!(ch->flags & FLAG_CLOCKEVENT)))
                __sh_cmt_set_next(ch, ch->max_match_value);
 out:
        raw_spin_unlock_irqrestore(&ch->lock, flags);

        return ret;
}

static void sh_cmt_stop(struct sh_cmt_channel *ch, unsigned long flag)
{
        unsigned long flags;
        unsigned long f;

        raw_spin_lock_irqsave(&ch->lock, flags);

        f = ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE);
        ch->flags &= ~flag;

        if (f && !(ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE)))
                sh_cmt_disable(ch);

        /* adjust the timeout to maximum if only clocksource left */
        if ((flag == FLAG_CLOCKEVENT) && (ch->flags & FLAG_CLOCKSOURCE))
                __sh_cmt_set_next(ch, ch->max_match_value);

        raw_spin_unlock_irqrestore(&ch->lock, flags);
}

static struct sh_cmt_channel *cs_to_sh_cmt(struct clocksource *cs)
{
        return container_of(cs, struct sh_cmt_channel, cs);
}

static cycle_t sh_cmt_clocksource_read(struct clocksource *cs)
{
        struct sh_cmt_channel *ch = cs_to_sh_cmt(cs);
        unsigned long flags, raw;
        unsigned long value;
        int has_wrapped;

        raw_spin_lock_irqsave(&ch->lock, flags);
        value = ch->total_cycles;
        raw = sh_cmt_get_counter(ch, &has_wrapped);

        if (unlikely(has_wrapped))
                raw += ch->match_value + 1;
        raw_spin_unlock_irqrestore(&ch->lock, flags);

        return value + raw;
}

static int sh_cmt_clocksource_enable(struct clocksource *cs)
{
        int ret;
        struct sh_cmt_channel *ch = cs_to_sh_cmt(cs);

        WARN_ON(ch->cs_enabled);

        ch->total_cycles = 0;

        ret = sh_cmt_start(ch, FLAG_CLOCKSOURCE);
        if (!ret) {
                __clocksource_update_freq_hz(cs, ch->rate);
                ch->cs_enabled = true;
        }
        return ret;
}

static void sh_cmt_clocksource_disable(struct clocksource *cs)
{
        struct sh_cmt_channel *ch = cs_to_sh_cmt(cs);

        WARN_ON(!ch->cs_enabled);

        sh_cmt_stop(ch, FLAG_CLOCKSOURCE);
        ch->cs_enabled = false;
}

static void sh_cmt_clocksource_suspend(struct clocksource *cs)
{
        struct sh_cmt_channel *ch = cs_to_sh_cmt(cs);

        sh_cmt_stop(ch, FLAG_CLOCKSOURCE);
        pm_genpd_syscore_poweroff(&ch->cmt->pdev->dev);
}

static void sh_cmt_clocksource_resume(struct clocksource *cs)
{
        struct sh_cmt_channel *ch = cs_to_sh_cmt(cs);

        pm_genpd_syscore_poweron(&ch->cmt->pdev->dev);
        sh_cmt_start(ch, FLAG_CLOCKSOURCE);
}

static int sh_cmt_register_clocksource(struct sh_cmt_channel *ch,
                                       const char *name)
{
        struct clocksource *cs = &ch->cs;

        cs->name = name;
        cs->rating = 125;
        cs->read = sh_cmt_clocksource_read;
        cs->enable = sh_cmt_clocksource_enable;
        cs->disable = sh_cmt_clocksource_disable;
        cs->suspend = sh_cmt_clocksource_suspend;
        cs->resume = sh_cmt_clocksource_resume;
        cs->mask = CLOCKSOURCE_MASK(sizeof(unsigned long) * 8);
        cs->flags = CLOCK_SOURCE_IS_CONTINUOUS;

        dev_info(&ch->cmt->pdev->dev, "ch%u: used as clock source\n",
                 ch->index);

        /* Register with dummy 1 Hz value, gets updated in ->enable() */
        clocksource_register_hz(cs, 1);
        return 0;
}

static struct sh_cmt_channel *ced_to_sh_cmt(struct clock_event_device *ced)
{
        return container_of(ced, struct sh_cmt_channel, ced);
}

static void sh_cmt_clock_event_start(struct sh_cmt_channel *ch, int periodic)
{
        struct clock_event_device *ced = &ch->ced;

        sh_cmt_start(ch, FLAG_CLOCKEVENT);

        /* TODO: calculate good shift from rate and counter bit width */

        ced->shift = 32;
        ced->mult = div_sc(ch->rate, NSEC_PER_SEC, ced->shift);
        ced->max_delta_ns = clockevent_delta2ns(ch->max_match_value, ced);
        ced->min_delta_ns = clockevent_delta2ns(0x1f, ced);

        if (periodic)
                sh_cmt_set_next(ch, ((ch->rate + HZ/2) / HZ) - 1);
        else
                sh_cmt_set_next(ch, ch->max_match_value);
}

static void sh_cmt_clock_event_mode(enum clock_event_mode mode,
                                    struct clock_event_device *ced)
{
        struct sh_cmt_channel *ch = ced_to_sh_cmt(ced);

        /* deal with old setting first */
        switch (ced->mode) {
        case CLOCK_EVT_MODE_PERIODIC:
        case CLOCK_EVT_MODE_ONESHOT:
                sh_cmt_stop(ch, FLAG_CLOCKEVENT);
                break;
        default:
                break;
        }

        switch (mode) {
        case CLOCK_EVT_MODE_PERIODIC:
                dev_info(&ch->cmt->pdev->dev,
                         "ch%u: used for periodic clock events\n", ch->index);
                sh_cmt_clock_event_start(ch, 1);
                break;
        case CLOCK_EVT_MODE_ONESHOT:
                dev_info(&ch->cmt->pdev->dev,
                         "ch%u: used for oneshot clock events\n", ch->index);
                sh_cmt_clock_event_start(ch, 0);
                break;
        case CLOCK_EVT_MODE_SHUTDOWN:
        case CLOCK_EVT_MODE_UNUSED:
                sh_cmt_stop(ch, FLAG_CLOCKEVENT);
                break;
        default:
                break;
        }
}

static int sh_cmt_clock_event_next(unsigned long delta,
                                   struct clock_event_device *ced)
{
        struct sh_cmt_channel *ch = ced_to_sh_cmt(ced);

        BUG_ON(ced->mode != CLOCK_EVT_MODE_ONESHOT);
        if (likely(ch->flags & FLAG_IRQCONTEXT))
                ch->next_match_value = delta - 1;
        else
                sh_cmt_set_next(ch, delta - 1);

        return 0;
}

static void sh_cmt_clock_event_suspend(struct clock_event_device *ced)
{
        struct sh_cmt_channel *ch = ced_to_sh_cmt(ced);

        pm_genpd_syscore_poweroff(&ch->cmt->pdev->dev);
        clk_unprepare(ch->cmt->clk);
}

static void sh_cmt_clock_event_resume(struct clock_event_device *ced)
{
        struct sh_cmt_channel *ch = ced_to_sh_cmt(ced);

        clk_prepare(ch->cmt->clk);
        pm_genpd_syscore_poweron(&ch->cmt->pdev->dev);
}

static int sh_cmt_register_clockevent(struct sh_cmt_channel *ch,
                                      const char *name)
{
        struct clock_event_device *ced = &ch->ced;
        int irq;
        int ret;

        irq = platform_get_irq(ch->cmt->pdev, ch->index);
        if (irq < 0) {
                dev_err(&ch->cmt->pdev->dev, "ch%u: failed to get irq\n",
                        ch->index);
                return irq;
        }

        ret = request_irq(irq, sh_cmt_interrupt,
                          IRQF_TIMER | IRQF_IRQPOLL | IRQF_NOBALANCING,
                          dev_name(&ch->cmt->pdev->dev), ch);
        if (ret) {
                dev_err(&ch->cmt->pdev->dev, "ch%u: failed to request irq %d\n",
                        ch->index, irq);
                return ret;
        }

        ced->name = name;
        ced->features = CLOCK_EVT_FEAT_PERIODIC;
        ced->features |= CLOCK_EVT_FEAT_ONESHOT;
        ced->rating = 125;
        ced->cpumask = cpu_possible_mask;
        ced->set_next_event = sh_cmt_clock_event_next;
        ced->set_mode = sh_cmt_clock_event_mode;
        ced->suspend = sh_cmt_clock_event_suspend;
        ced->resume = sh_cmt_clock_event_resume;

        dev_info(&ch->cmt->pdev->dev, "ch%u: used for clock events\n",
                 ch->index);
        clockevents_register_device(ced);

        return 0;
}

static int sh_cmt_register(struct sh_cmt_channel *ch, const char *name,
                           bool clockevent, bool clocksource)
{
        int ret;

        if (clockevent) {
                ch->cmt->has_clockevent = true;
                ret = sh_cmt_register_clockevent(ch, name);
                if (ret < 0)
                        return ret;
        }

        if (clocksource) {
                ch->cmt->has_clocksource = true;
                sh_cmt_register_clocksource(ch, name);
        }

        return 0;
}

static int sh_cmt_setup_channel(struct sh_cmt_channel *ch, unsigned int index,
                                unsigned int hwidx, bool clockevent,
                                bool clocksource, struct sh_cmt_device *cmt)
{
        int ret;

        /* Skip unused channels. */
        if (!clockevent && !clocksource)
                return 0;

        ch->cmt = cmt;
        ch->index = index;
        ch->hwidx = hwidx;

        /*
         * Compute the address of the channel control register block. For the
         * timers with a per-channel start/stop register, compute its address
         * as well.
         */
        switch (cmt->info->model) {
        case SH_CMT_16BIT:
                ch->ioctrl = cmt->mapbase + 2 + ch->hwidx * 6;
                break;
        case SH_CMT_32BIT:
        case SH_CMT_48BIT:
                ch->ioctrl = cmt->mapbase + 0x10 + ch->hwidx * 0x10;
                break;
        case SH_CMT_32BIT_FAST:
                /*
                 * The 32-bit "fast" timer has a single channel at hwidx 5 but
                 * is located at offset 0x40 instead of 0x60 for some reason.
                 */
                ch->ioctrl = cmt->mapbase + 0x40;
                break;
        case SH_CMT_48BIT_GEN2:
                ch->iostart = cmt->mapbase + ch->hwidx * 0x100;
                ch->ioctrl = ch->iostart + 0x10;
                break;
        }

        if (cmt->info->width == (sizeof(ch->max_match_value) * 8))
                ch->max_match_value = ~0;
        else
                ch->max_match_value = (1 << cmt->info->width) - 1;

        ch->match_value = ch->max_match_value;
        raw_spin_lock_init(&ch->lock);

        ch->timer_bit = cmt->info->model == SH_CMT_48BIT_GEN2 ? 0 : ch->hwidx;

        ret = sh_cmt_register(ch, dev_name(&cmt->pdev->dev),
                              clockevent, clocksource);
        if (ret) {
                dev_err(&cmt->pdev->dev, "ch%u: registration failed\n",
                        ch->index);
                return ret;
        }
        ch->cs_enabled = false;

        return 0;
}

static int sh_cmt_map_memory(struct sh_cmt_device *cmt)
{
        struct resource *mem;

        mem = platform_get_resource(cmt->pdev, IORESOURCE_MEM, 0);
        if (!mem) {
                dev_err(&cmt->pdev->dev, "failed to get I/O memory\n");
                return -ENXIO;
        }

        cmt->mapbase = ioremap_nocache(mem->start, resource_size(mem));
        if (cmt->mapbase == NULL) {
                dev_err(&cmt->pdev->dev, "failed to remap I/O memory\n");
                return -ENXIO;
        }

        return 0;
}

static const struct platform_device_id sh_cmt_id_table[] = {
        { "sh-cmt-16", (kernel_ulong_t)&sh_cmt_info[SH_CMT_16BIT] },
        { "sh-cmt-32", (kernel_ulong_t)&sh_cmt_info[SH_CMT_32BIT] },
        { "sh-cmt-32-fast", (kernel_ulong_t)&sh_cmt_info[SH_CMT_32BIT_FAST] },
        { "sh-cmt-48", (kernel_ulong_t)&sh_cmt_info[SH_CMT_48BIT] },
        { "sh-cmt-48-gen2", (kernel_ulong_t)&sh_cmt_info[SH_CMT_48BIT_GEN2] },
        { }
};
MODULE_DEVICE_TABLE(platform, sh_cmt_id_table);

static const struct of_device_id sh_cmt_of_table[] __maybe_unused = {
        { .compatible = "renesas,cmt-32", .data = &sh_cmt_info[SH_CMT_32BIT] },
        { .compatible = "renesas,cmt-32-fast", .data = &sh_cmt_info[SH_CMT_32BIT_FAST] },
        { .compatible = "renesas,cmt-48", .data = &sh_cmt_info[SH_CMT_48BIT] },
        { .compatible = "renesas,cmt-48-gen2", .data = &sh_cmt_info[SH_CMT_48BIT_GEN2] },
        { }
};
MODULE_DEVICE_TABLE(of, sh_cmt_of_table);

static int sh_cmt_parse_dt(struct sh_cmt_device *cmt)
{
        struct device_node *np = cmt->pdev->dev.of_node;

        return of_property_read_u32(np, "renesas,channels-mask",
                                    &cmt->hw_channels);
}

static int sh_cmt_setup(struct sh_cmt_device *cmt, struct platform_device *pdev)
{
        unsigned int mask;
        unsigned int i;
        int ret;

        memset(cmt, 0, sizeof(*cmt));
        cmt->pdev = pdev;
        raw_spin_lock_init(&cmt->lock);

        if (IS_ENABLED(CONFIG_OF) && pdev->dev.of_node) {
                const struct of_device_id *id;

                id = of_match_node(sh_cmt_of_table, pdev->dev.of_node);
                cmt->info = id->data;

                ret = sh_cmt_parse_dt(cmt);
                if (ret < 0)
                        return ret;
        } else if (pdev->dev.platform_data) {
                struct sh_timer_config *cfg = pdev->dev.platform_data;
                const struct platform_device_id *id = pdev->id_entry;

                cmt->info = (const struct sh_cmt_info *)id->driver_data;
                cmt->hw_channels = cfg->channels_mask;
        } else {
                dev_err(&cmt->pdev->dev, "missing platform data\n");
                return -ENXIO;
        }

        /* Get hold of clock. */
        cmt->clk = clk_get(&cmt->pdev->dev, "fck");
        if (IS_ERR(cmt->clk)) {
                dev_err(&cmt->pdev->dev, "cannot get clock\n");
                return PTR_ERR(cmt->clk);
        }

        ret = clk_prepare(cmt->clk);
        if (ret < 0)
                goto err_clk_put;

        /* Map the memory resource(s). */
        ret = sh_cmt_map_memory(cmt);
        if (ret < 0)
                goto err_clk_unprepare;

        /* Allocate and setup the channels. */
        cmt->num_channels = hweight8(cmt->hw_channels);
        cmt->channels = kzalloc(cmt->num_channels * sizeof(*cmt->channels),
                                GFP_KERNEL);
        if (cmt->channels == NULL) {
                ret = -ENOMEM;
                goto err_unmap;
        }

        /*
         * Use the first channel as a clock event device and the second channel
         * as a clock source. If only one channel is available use it for both.
         */
        for (i = 0, mask = cmt->hw_channels; i < cmt->num_channels; ++i) {
                unsigned int hwidx = ffs(mask) - 1;
                bool clocksource = i == 1 || cmt->num_channels == 1;
                bool clockevent = i == 0;

                ret = sh_cmt_setup_channel(&cmt->channels[i], i, hwidx,
                                           clockevent, clocksource, cmt);
                if (ret < 0)
                        goto err_unmap;

                mask &= ~(1 << hwidx);
        }

        platform_set_drvdata(pdev, cmt);

        return 0;

err_unmap:
        kfree(cmt->channels);
        iounmap(cmt->mapbase);
err_clk_unprepare:
        clk_unprepare(cmt->clk);
err_clk_put:
        clk_put(cmt->clk);
        return ret;
}

static int sh_cmt_probe(struct platform_device *pdev)
{
        struct sh_cmt_device *cmt = platform_get_drvdata(pdev);
        int ret;

        if (!is_early_platform_device(pdev)) {
                pm_runtime_set_active(&pdev->dev);
                pm_runtime_enable(&pdev->dev);
        }

        if (cmt) {
                dev_info(&pdev->dev, "kept as earlytimer\n");
                goto out;
        }

        cmt = kzalloc(sizeof(*cmt), GFP_KERNEL);
        if (cmt == NULL)
                return -ENOMEM;

        ret = sh_cmt_setup(cmt, pdev);
        if (ret) {
                kfree(cmt);
                pm_runtime_idle(&pdev->dev);
                return ret;
        }
        if (is_early_platform_device(pdev))
                return 0;

 out:
        if (cmt->has_clockevent || cmt->has_clocksource)
                pm_runtime_irq_safe(&pdev->dev);
        else
                pm_runtime_idle(&pdev->dev);

        return 0;
}

static int sh_cmt_remove(struct platform_device *pdev)
{
        return -EBUSY; /* cannot unregister clockevent and clocksource */
}

static struct platform_driver sh_cmt_device_driver = {
        .probe          = sh_cmt_probe,
        .remove         = sh_cmt_remove,
        .driver         = {
                .name   = "sh_cmt",
                .of_match_table = of_match_ptr(sh_cmt_of_table),
        },
        .id_table       = sh_cmt_id_table,
};

static int __init sh_cmt_init(void)
{
        return platform_driver_register(&sh_cmt_device_driver);
}

static void __exit sh_cmt_exit(void)
{
        platform_driver_unregister(&sh_cmt_device_driver);
}

early_platform_init("earlytimer", &sh_cmt_device_driver);
subsys_initcall(sh_cmt_init);
module_exit(sh_cmt_exit);

MODULE_AUTHOR("Magnus Damm");
MODULE_DESCRIPTION("SuperH CMT Timer Driver");
MODULE_LICENSE("GPL v2");