#include <linux/init.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/irq.h>

#include <linux/clk.h>
#include <linux/err.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/platform_device.h>
#include <linux/atmel_tc.h>


/*
 * We're configured to use a specific TC block, one that's not hooked
 * up to external hardware, to provide a time solution:
 *
 *   - Two channels combine to create a free-running 32 bit counter
 *     with a base rate of 5+ MHz, packaged as a clocksource (with
 *     resolution better than 200 nsec).
 *
 *   - The third channel may be used to provide a 16-bit clockevent
 *     source, used in either periodic or oneshot mode.  This runs
 *     at 32 KiHZ, and can handle delays of up to two seconds.
 *
 * A boot clocksource and clockevent source are also currently needed,
 * unless the relevant platforms (ARM/AT91, AVR32/AT32) are changed so
 * this code can be used when init_timers() is called, well before most
 * devices are set up.  (Some low end AT91 parts, which can run uClinux,
 * have only the timers in one TC block... they currently don't support
 * the tclib code, because of that initialization issue.)
 *
 * REVISIT behavior during system suspend states... we should disable
 * all clocks and save the power.  Easily done for clockevent devices,
 * but clocksources won't necessarily get the needed notifications.
 * For deeper system sleep states, this will be mandatory...
 */

static void __iomem *tcaddr;

static cycle_t tc_get_cycles(struct clocksource *cs)
{
        unsigned long   flags;
        u32             lower, upper;

        raw_local_irq_save(flags);
        do {
                upper = __raw_readl(tcaddr + ATMEL_TC_REG(1, CV));
                lower = __raw_readl(tcaddr + ATMEL_TC_REG(0, CV));
        } while (upper != __raw_readl(tcaddr + ATMEL_TC_REG(1, CV)));

        raw_local_irq_restore(flags);
        return (upper << 16) | lower;
}

static struct clocksource clksrc = {
        .name           = "tcb_clksrc",
        .rating         = 200,
        .read           = tc_get_cycles,
        .mask           = CLOCKSOURCE_MASK(32),
        .shift          = 18,
        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
};

#ifdef CONFIG_GENERIC_CLOCKEVENTS

struct tc_clkevt_device {
        struct clock_event_device       clkevt;
        struct clk                      *clk;
        void __iomem                    *regs;
};

static struct tc_clkevt_device *to_tc_clkevt(struct clock_event_device *clkevt)
{
        return container_of(clkevt, struct tc_clkevt_device, clkevt);
}

/* For now, we always use the 32K clock ... this optimizes for NO_HZ,
 * because using one of the divided clocks would usually mean the
 * tick rate can never be less than several dozen Hz (vs 0.5 Hz).
 *
 * A divided clock could be good for high resolution timers, since
 * 30.5 usec resolution can seem "low".
 */
static u32 timer_clock;

static void tc_mode(enum clock_event_mode m, struct clock_event_device *d)
{
        struct tc_clkevt_device *tcd = to_tc_clkevt(d);
        void __iomem            *regs = tcd->regs;

        if (tcd->clkevt.mode == CLOCK_EVT_MODE_PERIODIC
                        || tcd->clkevt.mode == CLOCK_EVT_MODE_ONESHOT) {
                __raw_writel(0xff, regs + ATMEL_TC_REG(2, IDR));
                __raw_writel(ATMEL_TC_CLKDIS, regs + ATMEL_TC_REG(2, CCR));
                clk_disable(tcd->clk);
        }

        switch (m) {

        /* By not making the gentime core emulate periodic mode on top
         * of oneshot, we get lower overhead and improved accuracy.
         */
        case CLOCK_EVT_MODE_PERIODIC:
                clk_enable(tcd->clk);

                /* slow clock, count up to RC, then irq and restart */
                __raw_writel(timer_clock
                                | ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
                                regs + ATMEL_TC_REG(2, CMR));
                __raw_writel((32768 + HZ/2) / HZ, tcaddr + ATMEL_TC_REG(2, RC));

                /* Enable clock and interrupts on RC compare */
                __raw_writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));

                /* go go gadget! */
                __raw_writel(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG,
                                regs + ATMEL_TC_REG(2, CCR));
                break;

        case CLOCK_EVT_MODE_ONESHOT:
                clk_enable(tcd->clk);

                /* slow clock, count up to RC, then irq and stop */
                __raw_writel(timer_clock | ATMEL_TC_CPCSTOP
                                | ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
                                regs + ATMEL_TC_REG(2, CMR));
                __raw_writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));

                /* set_next_event() configures and starts the timer */
                break;

        default:
                break;
        }
}

static int tc_next_event(unsigned long delta, struct clock_event_device *d)
{
        __raw_writel(delta, tcaddr + ATMEL_TC_REG(2, RC));

        /* go go gadget! */
        __raw_writel(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG,
                        tcaddr + ATMEL_TC_REG(2, CCR));
        return 0;
}

static struct tc_clkevt_device clkevt = {
        .clkevt = {
                .name           = "tc_clkevt",
                .features       = CLOCK_EVT_FEAT_PERIODIC
                                        | CLOCK_EVT_FEAT_ONESHOT,
                .shift          = 32,
                /* Should be lower than at91rm9200's system timer */
                .rating         = 125,
                .set_next_event = tc_next_event,
                .set_mode       = tc_mode,
        },
};

static irqreturn_t ch2_irq(int irq, void *handle)
{
        struct tc_clkevt_device *dev = handle;
        unsigned int            sr;

        sr = __raw_readl(dev->regs + ATMEL_TC_REG(2, SR));
        if (sr & ATMEL_TC_CPCS) {
                dev->clkevt.event_handler(&dev->clkevt);
                return IRQ_HANDLED;
        }

        return IRQ_NONE;
}

static struct irqaction tc_irqaction = {
        .name           = "tc_clkevt",
        .flags          = IRQF_TIMER | IRQF_DISABLED,
        .handler        = ch2_irq,
};

static void __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
{
        struct clk *t2_clk = tc->clk[2];
        int irq = tc->irq[2];

        clkevt.regs = tc->regs;
        clkevt.clk = t2_clk;
        tc_irqaction.dev_id = &clkevt;

        timer_clock = clk32k_divisor_idx;

        clkevt.clkevt.mult = div_sc(32768, NSEC_PER_SEC, clkevt.clkevt.shift);
        clkevt.clkevt.max_delta_ns
                = clockevent_delta2ns(0xffff, &clkevt.clkevt);
        clkevt.clkevt.min_delta_ns = clockevent_delta2ns(1, &clkevt.clkevt) + 1;
        clkevt.clkevt.cpumask = cpumask_of(0);

        setup_irq(irq, &tc_irqaction);

        clockevents_register_device(&clkevt.clkevt);
}

#else /* !CONFIG_GENERIC_CLOCKEVENTS */

static void __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
{
        /* NOTHING */
}

#endif

static int __init tcb_clksrc_init(void)
{
        static char bootinfo[] __initdata
                = KERN_DEBUG "%s: tc%d at %d.%03d MHz\n";

        struct platform_device *pdev;
        struct atmel_tc *tc;
        struct clk *t0_clk;
        u32 rate, divided_rate = 0;
        int best_divisor_idx = -1;
        int clk32k_divisor_idx = -1;
        int i;

        tc = atmel_tc_alloc(CONFIG_ATMEL_TCB_CLKSRC_BLOCK, clksrc.name);
        if (!tc) {
                pr_debug("can't alloc TC for clocksource\n");
                return -ENODEV;
        }
        tcaddr = tc->regs;
        pdev = tc->pdev;

        t0_clk = tc->clk[0];
        clk_enable(t0_clk);

        /* How fast will we be counting?  Pick something over 5 MHz.  */
        rate = (u32) clk_get_rate(t0_clk);
        for (i = 0; i < 5; i++) {
                unsigned divisor = atmel_tc_divisors[i];
                unsigned tmp;

                /* remember 32 KiHz clock for later */
                if (!divisor) {
                        clk32k_divisor_idx = i;
                        continue;
                }

                tmp = rate / divisor;
                pr_debug("TC: %u / %-3u [%d] --> %u\n", rate, divisor, i, tmp);
                if (best_divisor_idx > 0) {
                        if (tmp < 5 * 1000 * 1000)
                                continue;
                }
                divided_rate = tmp;
                best_divisor_idx = i;
        }

        clksrc.mult = clocksource_hz2mult(divided_rate, clksrc.shift);

        printk(bootinfo, clksrc.name, CONFIG_ATMEL_TCB_CLKSRC_BLOCK,
                        divided_rate / 1000000,
                        ((divided_rate + 500000) % 1000000) / 1000);

        /* tclib will give us three clocks no matter what the
         * underlying platform supports.
         */
        clk_enable(tc->clk[1]);

        /* channel 0:  waveform mode, input mclk/8, clock TIOA0 on overflow */
        __raw_writel(best_divisor_idx                   /* likely divide-by-8 */
                        | ATMEL_TC_WAVE
                        | ATMEL_TC_WAVESEL_UP           /* free-run */
                        | ATMEL_TC_ACPA_SET             /* TIOA0 rises at 0 */
                        | ATMEL_TC_ACPC_CLEAR,          /* (duty cycle 50%) */
                        tcaddr + ATMEL_TC_REG(0, CMR));
        __raw_writel(0x0000, tcaddr + ATMEL_TC_REG(0, RA));
        __raw_writel(0x8000, tcaddr + ATMEL_TC_REG(0, RC));
        __raw_writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR));      /* no irqs */
        __raw_writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));

        /* channel 1:  waveform mode, input TIOA0 */
        __raw_writel(ATMEL_TC_XC1                       /* input: TIOA0 */
                        | ATMEL_TC_WAVE
                        | ATMEL_TC_WAVESEL_UP,          /* free-run */
                        tcaddr + ATMEL_TC_REG(1, CMR));
        __raw_writel(0xff, tcaddr + ATMEL_TC_REG(1, IDR));      /* no irqs */
        __raw_writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(1, CCR));

        /* chain channel 0 to channel 1, then reset all the timers */
        __raw_writel(ATMEL_TC_TC1XC1S_TIOA0, tcaddr + ATMEL_TC_BMR);
        __raw_writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);

        /* and away we go! */
        clocksource_register(&clksrc);

        /* channel 2:  periodic and oneshot timer support */
        setup_clkevents(tc, clk32k_divisor_idx);

        return 0;
}
arch_initcall(tcb_clksrc_init);