#include <linux/module.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/atmel_pwm.h>


/*
 * This is a simple driver for the PWM controller found in various newer
 * Atmel SOCs, including the AVR32 series and the AT91sam9263.
 *
 * Chips with current Linux ports have only 4 PWM channels, out of max 32.
 * AT32UC3A and AT32UC3B chips have 7 channels (but currently no Linux).
 * Docs are inconsistent about the width of the channel counter registers;
 * it's at least 16 bits, but several places say 20 bits.
 */
#define PWM_NCHAN       4               /* max 32 */

struct pwm {
        spinlock_t              lock;
        struct platform_device  *pdev;
        u32                     mask;
        int                     irq;
        void __iomem            *base;
        struct clk              *clk;
        struct pwm_channel      *channel[PWM_NCHAN];
        void                    (*handler[PWM_NCHAN])(struct pwm_channel *);
};


/* global PWM controller registers */
#define PWM_MR          0x00
#define PWM_ENA         0x04
#define PWM_DIS         0x08
#define PWM_SR          0x0c
#define PWM_IER         0x10
#define PWM_IDR         0x14
#define PWM_IMR         0x18
#define PWM_ISR         0x1c

static inline void pwm_writel(const struct pwm *p, unsigned offset, u32 val)
{
        __raw_writel(val, p->base + offset);
}

static inline u32 pwm_readl(const struct pwm *p, unsigned offset)
{
        return __raw_readl(p->base + offset);
}

static inline void __iomem *pwmc_regs(const struct pwm *p, int index)
{
        return p->base + 0x200 + index * 0x20;
}

static struct pwm *pwm;

static void pwm_dumpregs(struct pwm_channel *ch, char *tag)
{
        struct device   *dev = &pwm->pdev->dev;

        dev_dbg(dev, "%s: mr %08x, sr %08x, imr %08x\n",
                tag,
                pwm_readl(pwm, PWM_MR),
                pwm_readl(pwm, PWM_SR),
                pwm_readl(pwm, PWM_IMR));
        dev_dbg(dev,
                "pwm ch%d - mr %08x, dty %u, prd %u, cnt %u\n",
                ch->index,
                pwm_channel_readl(ch, PWM_CMR),
                pwm_channel_readl(ch, PWM_CDTY),
                pwm_channel_readl(ch, PWM_CPRD),
                pwm_channel_readl(ch, PWM_CCNT));
}


/**
 * pwm_channel_alloc - allocate an unused PWM channel
 * @index: identifies the channel
 * @ch: structure to be initialized
 *
 * Drivers allocate PWM channels according to the board's wiring, and
 * matching board-specific setup code.  Returns zero or negative errno.
 */
int pwm_channel_alloc(int index, struct pwm_channel *ch)
{
        unsigned long   flags;
        int             status = 0;

        /* insist on PWM init, with this signal pinned out */
        if (!pwm || !(pwm->mask & 1 << index))
                return -ENODEV;

        if (index < 0 || index >= PWM_NCHAN || !ch)
                return -EINVAL;
        memset(ch, 0, sizeof *ch);

        spin_lock_irqsave(&pwm->lock, flags);
        if (pwm->channel[index])
                status = -EBUSY;
        else {
                clk_enable(pwm->clk);

                ch->regs = pwmc_regs(pwm, index);
                ch->index = index;

                /* REVISIT: ap7000 seems to go 2x as fast as we expect!! */
                ch->mck = clk_get_rate(pwm->clk);

                pwm->channel[index] = ch;
                pwm->handler[index] = NULL;

                /* channel and irq are always disabled when we return */
                pwm_writel(pwm, PWM_DIS, 1 << index);
                pwm_writel(pwm, PWM_IDR, 1 << index);
        }
        spin_unlock_irqrestore(&pwm->lock, flags);
        return status;
}
EXPORT_SYMBOL(pwm_channel_alloc);

static int pwmcheck(struct pwm_channel *ch)
{
        int             index;

        if (!pwm)
                return -ENODEV;
        if (!ch)
                return -EINVAL;
        index = ch->index;
        if (index < 0 || index >= PWM_NCHAN || pwm->channel[index] != ch)
                return -EINVAL;

        return index;
}

/**
 * pwm_channel_free - release a previously allocated channel
 * @ch: the channel being released
 *
 * The channel is completely shut down (counter and IRQ disabled),
 * and made available for re-use.  Returns zero, or negative errno.
 */
int pwm_channel_free(struct pwm_channel *ch)
{
        unsigned long   flags;
        int             t;

        spin_lock_irqsave(&pwm->lock, flags);
        t = pwmcheck(ch);
        if (t >= 0) {
                pwm->channel[t] = NULL;
                pwm->handler[t] = NULL;

                /* channel and irq are always disabled when we return */
                pwm_writel(pwm, PWM_DIS, 1 << t);
                pwm_writel(pwm, PWM_IDR, 1 << t);

                clk_disable(pwm->clk);
                t = 0;
        }
        spin_unlock_irqrestore(&pwm->lock, flags);
        return t;
}
EXPORT_SYMBOL(pwm_channel_free);

int __pwm_channel_onoff(struct pwm_channel *ch, int enabled)
{
        unsigned long   flags;
        int             t;

        /* OMITTED FUNCTIONALITY:  starting several channels in synch */

        spin_lock_irqsave(&pwm->lock, flags);
        t = pwmcheck(ch);
        if (t >= 0) {
                pwm_writel(pwm, enabled ? PWM_ENA : PWM_DIS, 1 << t);
                t = 0;
                pwm_dumpregs(ch, enabled ? "enable" : "disable");
        }
        spin_unlock_irqrestore(&pwm->lock, flags);

        return t;
}
EXPORT_SYMBOL(__pwm_channel_onoff);

/**
 * pwm_clk_alloc - allocate and configure CLKA or CLKB
 * @prescale: from 0..10, the power of two used to divide MCK
 * @div: from 1..255, the linear divisor to use
 *
 * Returns PWM_CPR_CLKA, PWM_CPR_CLKB, or negative errno.  The allocated
 * clock will run with a period of (2^prescale * div) / MCK, or twice as
 * long if center aligned PWM output is used.  The clock must later be
 * deconfigured using pwm_clk_free().
 */
int pwm_clk_alloc(unsigned prescale, unsigned div)
{
        unsigned long   flags;
        u32             mr;
        u32             val = (prescale << 8) | div;
        int             ret = -EBUSY;

        if (prescale >= 10 || div == 0 || div > 255)
                return -EINVAL;

        spin_lock_irqsave(&pwm->lock, flags);
        mr = pwm_readl(pwm, PWM_MR);
        if ((mr & 0xffff) == 0) {
                mr |= val;
                ret = PWM_CPR_CLKA;
        } else if ((mr & (0xffff << 16)) == 0) {
                mr |= val << 16;
                ret = PWM_CPR_CLKB;
        }
        if (ret > 0)
                pwm_writel(pwm, PWM_MR, mr);
        spin_unlock_irqrestore(&pwm->lock, flags);
        return ret;
}
EXPORT_SYMBOL(pwm_clk_alloc);

/**
 * pwm_clk_free - deconfigure and release CLKA or CLKB
 *
 * Reverses the effect of pwm_clk_alloc().
 */
void pwm_clk_free(unsigned clk)
{
        unsigned long   flags;
        u32             mr;

        spin_lock_irqsave(&pwm->lock, flags);
        mr = pwm_readl(pwm, PWM_MR);
        if (clk == PWM_CPR_CLKA)
                pwm_writel(pwm, PWM_MR, mr & ~(0xffff << 0));
        if (clk == PWM_CPR_CLKB)
                pwm_writel(pwm, PWM_MR, mr & ~(0xffff << 16));
        spin_unlock_irqrestore(&pwm->lock, flags);
}
EXPORT_SYMBOL(pwm_clk_free);

/**
 * pwm_channel_handler - manage channel's IRQ handler
 * @ch: the channel
 * @handler: the handler to use, possibly NULL
 *
 * If the handler is non-null, the handler will be called after every
 * period of this PWM channel.  If the handler is null, this channel
 * won't generate an IRQ.
 */
int pwm_channel_handler(struct pwm_channel *ch,
                void (*handler)(struct pwm_channel *ch))
{
        unsigned long   flags;
        int             t;

        spin_lock_irqsave(&pwm->lock, flags);
        t = pwmcheck(ch);
        if (t >= 0) {
                pwm->handler[t] = handler;
                pwm_writel(pwm, handler ? PWM_IER : PWM_IDR, 1 << t);
                t = 0;
        }
        spin_unlock_irqrestore(&pwm->lock, flags);

        return t;
}
EXPORT_SYMBOL(pwm_channel_handler);

static irqreturn_t pwm_irq(int id, void *_pwm)
{
        struct pwm      *p = _pwm;
        irqreturn_t     handled = IRQ_NONE;
        u32             irqstat;
        int             index;

        spin_lock(&p->lock);

        /* ack irqs, then handle them */
        irqstat = pwm_readl(pwm, PWM_ISR);

        while (irqstat) {
                struct pwm_channel *ch;
                void (*handler)(struct pwm_channel *ch);

                index = ffs(irqstat) - 1;
                irqstat &= ~(1 << index);
                ch = pwm->channel[index];
                handler = pwm->handler[index];
                if (handler && ch) {
                        spin_unlock(&p->lock);
                        handler(ch);
                        spin_lock(&p->lock);
                        handled = IRQ_HANDLED;
                }
        }

        spin_unlock(&p->lock);
        return handled;
}

static int __init pwm_probe(struct platform_device *pdev)
{
        struct resource *r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        int irq = platform_get_irq(pdev, 0);
        u32 *mp = pdev->dev.platform_data;
        struct pwm *p;
        int status = -EIO;

        if (pwm)
                return -EBUSY;
        if (!r || irq < 0 || !mp || !*mp)
                return -ENODEV;
        if (*mp & ~((1<<PWM_NCHAN)-1)) {
                dev_warn(&pdev->dev, "mask 0x%x ... more than %d channels\n",
                        *mp, PWM_NCHAN);
                return -EINVAL;
        }

        p = kzalloc(sizeof(*p), GFP_KERNEL);
        if (!p)
                return -ENOMEM;

        spin_lock_init(&p->lock);
        p->pdev = pdev;
        p->mask = *mp;
        p->irq = irq;
        p->base = ioremap(r->start, r->end - r->start + 1);
        if (!p->base)
                goto fail;
        p->clk = clk_get(&pdev->dev, "pwm_clk");
        if (IS_ERR(p->clk)) {
                status = PTR_ERR(p->clk);
                p->clk = NULL;
                goto fail;
        }

        status = request_irq(irq, pwm_irq, 0, pdev->name, p);
        if (status < 0)
                goto fail;

        pwm = p;
        platform_set_drvdata(pdev, p);

        return 0;

fail:
        if (p->clk)
                clk_put(p->clk);
        if (p->base)
                iounmap(p->base);

        kfree(p);
        return status;
}

static int __exit pwm_remove(struct platform_device *pdev)
{
        struct pwm *p = platform_get_drvdata(pdev);

        if (p != pwm)
                return -EINVAL;

        clk_enable(pwm->clk);
        pwm_writel(pwm, PWM_DIS, (1 << PWM_NCHAN) - 1);
        pwm_writel(pwm, PWM_IDR, (1 << PWM_NCHAN) - 1);
        clk_disable(pwm->clk);

        pwm = NULL;

        free_irq(p->irq, p);
        clk_put(p->clk);
        iounmap(p->base);
        kfree(p);

        return 0;
}

static struct platform_driver atmel_pwm_driver = {
        .driver = {
                .name = "atmel_pwm",
                .owner = THIS_MODULE,
        },
        .remove = __exit_p(pwm_remove),

        /* NOTE: PWM can keep running in AVR32 "idle" and "frozen" states;
         * and all AT91sam9263 states, albeit at reduced clock rate if
         * MCK becomes the slow clock (i.e. what Linux labels STR).
         */
};

static int __init pwm_init(void)
{
        return platform_driver_probe(&atmel_pwm_driver, pwm_probe);
}
module_init(pwm_init);

static void __exit pwm_exit(void)
{
        platform_driver_unregister(&atmel_pwm_driver);
}
module_exit(pwm_exit);

MODULE_DESCRIPTION("Driver for AT32/AT91 PWM module");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:atmel_pwm");