/*-
 * Copyright (c) 2014 Tycho Nightingale <tycho.nightingale@pluribusnetworks.com>
 * Copyright (c) 2011 NetApp, Inc.
 * Copyright (c) 2015 xhyve developers
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY NETAPP, INC ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL NETAPP, INC OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <stdint.h>
#include <stdbool.h>
#include <assert.h>
#include <libkern/OSAtomic.h>
#include <xhyve/support/timerreg.h>
#include <xhyve/vmm/vmm_callout.h>
#include <xhyve/vmm/vmm_ktr.h>
#include <xhyve/vmm/io/vatpic.h>
#include <xhyve/vmm/io/vatpit.h>
#include <xhyve/vmm/io/vioapic.h>

#define VATPIT_LOCK_INIT(v) (v)->lock = OS_SPINLOCK_INIT;
#define VATPIT_LOCK(v) OSSpinLockLock(&(v)->lock)
#define VATPIT_UNLOCK(v) OSSpinLockUnlock(&(v)->lock)

#define	TIMER_SEL_MASK		0xc0
#define	TIMER_RW_MASK		0x30
#define	TIMER_MODE_MASK		0x0f
#define	TIMER_SEL_READBACK	0xc0

#define	TIMER_STS_OUT		0x80
#define	TIMER_STS_NULLCNT	0x40

#define	TIMER_RB_LCTR		0x20
#define	TIMER_RB_LSTATUS	0x10
#define	TIMER_RB_CTR_2		0x08
#define	TIMER_RB_CTR_1		0x04
#define	TIMER_RB_CTR_0		0x02

#define	TMR2_OUT_STS		0x20

#define	PIT_8254_FREQ		1193182
#define	TIMER_DIV(freq, hz)	(((freq) + (hz) / 2) / (hz))

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wpadded"
struct vatpit_callout_arg {
	struct vatpit *vatpit;
	int channel_num;
};

struct channel {
	int mode;
	uint16_t initial; /* initial counter value */
	sbintime_t now_sbt; /* uptime when counter was loaded */
	uint8_t cr[2];
	uint8_t ol[2];
	bool slatched; /* status latched */
	uint8_t status;
	int crbyte;
	int olbyte;
	int frbyte;
	struct callout callout;
	sbintime_t callout_sbt; /* target time */
	struct vatpit_callout_arg callout_arg;
};

struct vatpit {
	struct vm *vm;
	OSSpinLock lock;
	sbintime_t freq_sbt;
	struct channel channel[3];
};
#pragma clang diagnostic pop

static void pit_timer_start_cntr0(struct vatpit *vatpit);

static int
vatpit_get_out(struct vatpit *vatpit, int channel)
{
	struct channel *c;
	sbintime_t delta_ticks;
	int out;

	c = &vatpit->channel[channel];

	switch (c->mode) {
	case TIMER_INTTC:
		delta_ticks = (sbinuptime() - c->now_sbt) / vatpit->freq_sbt;
		out = ((c->initial - delta_ticks) <= 0);
		break;
	default:
		out = 0;
		break;
	}

	return (out);
}

static void
vatpit_callout_handler(void *a)
{
	struct vatpit_callout_arg *arg = a;
	struct vatpit *vatpit;
	struct callout *callout;
	struct channel *c;

	vatpit = arg->vatpit;
	c = &vatpit->channel[arg->channel_num];
	callout = &c->callout;

	VM_CTR1(vatpit->vm, "atpit t%d fired", arg->channel_num);

	VATPIT_LOCK(vatpit);

	if (callout_pending(callout))		/* callout was reset */
		goto done;

	if (!callout_active(callout))		/* callout was stopped */
		goto done;

	callout_deactivate(callout);

	if (c->mode == TIMER_RATEGEN) {
		pit_timer_start_cntr0(vatpit);
	}

	vatpic_pulse_irq(vatpit->vm, 0);
	vioapic_pulse_irq(vatpit->vm, 2);

done:
	VATPIT_UNLOCK(vatpit);
	return;
}

static void
pit_timer_start_cntr0(struct vatpit *vatpit)
{
	struct channel *c;
	sbintime_t now, delta;

	c = &vatpit->channel[0];
	if (c->initial != 0) {
		delta = c->initial * vatpit->freq_sbt;
		c->callout_sbt = c->callout_sbt + delta;

		/*
		 * Reset 'callout_sbt' if the time that the callout
		 * was supposed to fire is more than 'c->initial'
		 * ticks in the past.
		 */
		now = sbinuptime();
		if (c->callout_sbt < now)
			c->callout_sbt = now + delta;

		callout_reset_sbt(&c->callout, c->callout_sbt,
		    0, vatpit_callout_handler, &c->callout_arg,
		    C_ABSOLUTE);
	}
}

static uint16_t
pit_update_counter(struct vatpit *vatpit, struct channel *c, bool latch)
{
	uint16_t lval;
	sbintime_t delta_ticks;

	/* cannot latch a new value until the old one has been consumed */
	if (latch && c->olbyte != 0)
		return (0);

	if (c->initial == 0) {
		/*
		 * This is possibly an o/s bug - reading the value of
		 * the timer without having set up the initial value.
		 *
		 * The original user-space version of this code set
		 * the timer to 100hz in this condition; do the same
		 * here.
		 */
		c->initial = TIMER_DIV(PIT_8254_FREQ, 100);
		c->now_sbt = sbinuptime();
		c->status &= ~TIMER_STS_NULLCNT;
	}

	delta_ticks = (sbinuptime() - c->now_sbt) / vatpit->freq_sbt;

	lval = c->initial - delta_ticks % c->initial;

	if (latch) {
		c->olbyte = 2;
		c->ol[1] = (uint8_t) lval; /* LSB */
		c->ol[0] = (uint8_t) (lval >> 8); /* MSB */
	}

	return (lval);
}

static int
pit_readback1(struct vatpit *vatpit, int channel, uint8_t cmd)
{
	struct channel *c;

	c = &vatpit->channel[channel];

	/*
	 * Latch the count/status of the timer if not already latched.
	 * N.B. that the count/status latch-select bits are active-low.
	 */
	if (!(cmd & TIMER_RB_LCTR) && !c->olbyte) {
		(void) pit_update_counter(vatpit, c, true);
	}

	if (!(cmd & TIMER_RB_LSTATUS) && !c->slatched) {
		c->slatched = true;
		/*
		 * For mode 0, see if the elapsed time is greater
		 * than the initial value - this results in the
		 * output pin being set to 1 in the status byte.
		 */
		if (c->mode == TIMER_INTTC && vatpit_get_out(vatpit, channel))
			c->status |= TIMER_STS_OUT;
		else
			c->status &= ~TIMER_STS_OUT;
	}

	return (0);
}

static int
pit_readback(struct vatpit *vatpit, uint8_t cmd)
{
	int error;

	/*
	 * The readback command can apply to all timers.
	 */
	error = 0;
	if (cmd & TIMER_RB_CTR_0)
		error = pit_readback1(vatpit, 0, cmd);
	if (!error && cmd & TIMER_RB_CTR_1)
		error = pit_readback1(vatpit, 1, cmd);
	if (!error && cmd & TIMER_RB_CTR_2)
		error = pit_readback1(vatpit, 2, cmd);

	return (error);
}


static int
vatpit_update_mode(struct vatpit *vatpit, uint8_t val)
{
	struct channel *c;
	int sel, rw, mode;

	sel = val & TIMER_SEL_MASK;
	rw = val & TIMER_RW_MASK;
	mode = val & TIMER_MODE_MASK;

	if (sel == TIMER_SEL_READBACK)
		return (pit_readback(vatpit, val));

	if (rw != TIMER_LATCH && rw != TIMER_16BIT)
		return (-1);

	if (rw != TIMER_LATCH) {
		/*
		 * Counter mode is not affected when issuing a
		 * latch command.
		 */
		if (mode != TIMER_INTTC &&
		    mode != TIMER_RATEGEN &&
		    mode != TIMER_SQWAVE &&
		    mode != TIMER_SWSTROBE)
			return (-1);
	}

	c = &vatpit->channel[sel >> 6];
	if (rw == TIMER_LATCH)
		pit_update_counter(vatpit, c, true);
	else {
		c->mode = mode;
		c->olbyte = 0;	/* reset latch after reprogramming */
		c->status |= TIMER_STS_NULLCNT;
	}

	return (0);
}

int
vatpit_handler(struct vm *vm, UNUSED int vcpuid, bool in, int port, int bytes,
    uint32_t *eax)
{
	struct vatpit *vatpit;
	struct channel *c;
	uint8_t val;
	int error;

	vatpit = vm_atpit(vm);

	if (bytes != 1)
		return (-1);

	val = (uint8_t) *eax;

	if (port == TIMER_MODE) {
		if (in) {
			VM_CTR0(vatpit->vm, "vatpit attempt to read mode");
			return (-1);
		}

		VATPIT_LOCK(vatpit);
		error = vatpit_update_mode(vatpit, val);
		VATPIT_UNLOCK(vatpit);

		return (error);
	}

	/* counter ports */
	KASSERT(port >= TIMER_CNTR0 && port <= TIMER_CNTR2,
	    ("invalid port 0x%x\n", port));
	c = &vatpit->channel[port - TIMER_CNTR0];

	VATPIT_LOCK(vatpit);
	if (in && c->slatched) {
		/*
		 * Return the status byte if latched
		 */
		*eax = c->status;
		c->slatched = false;
		c->status = 0;
	} else if (in) {
		/*
		 * The spec says that once the output latch is completely
		 * read it should revert to "following" the counter. Use
		 * the free running counter for this case (i.e. Linux
		 * TSC calibration). Assuming the access mode is 16-bit,
		 * toggle the MSB/LSB bit on each read.
		 */
		if (c->olbyte == 0) {
			uint16_t tmp;

			tmp = pit_update_counter(vatpit, c, false);
			if (c->frbyte)
				tmp >>= 8;
			tmp &= 0xff;
			*eax = tmp;
			c->frbyte ^= 1;
		}  else
			*eax = c->ol[--c->olbyte];
	} else {
		c->cr[c->crbyte++] = (uint8_t) *eax;
		if (c->crbyte == 2) {
			c->status &= ~TIMER_STS_NULLCNT;
			c->frbyte = 0;
			c->crbyte = 0;
			c->initial = (uint16_t) c->cr[0];
			c->initial |= (((uint16_t) c->cr[1]) << 8);
			c->now_sbt = sbinuptime();
			/* Start an interval timer for channel 0 */
			if (port == TIMER_CNTR0) {
				c->callout_sbt = c->now_sbt;
				pit_timer_start_cntr0(vatpit);
			}
			if (c->initial == 0)
				c->initial = 0xffff;
		}
	}
	VATPIT_UNLOCK(vatpit);

	return (0);
}

int
vatpit_nmisc_handler(struct vm *vm, UNUSED int vcpuid, bool in, UNUSED int port,
	UNUSED int bytes, uint32_t *eax)
{
	struct vatpit *vatpit;

	vatpit = vm_atpit(vm);

	if (in) {
			VATPIT_LOCK(vatpit);
			if (vatpit_get_out(vatpit, 2))
				*eax = TMR2_OUT_STS;
			else
				*eax = 0;

			VATPIT_UNLOCK(vatpit);
	}

	return (0);
}

struct vatpit *
vatpit_init(struct vm *vm)
{
	struct vatpit *vatpit;
	struct bintime bt;
	struct vatpit_callout_arg *arg;
	int i;

	vatpit = malloc(sizeof(struct vatpit));
	assert(vatpit);
	bzero(vatpit, sizeof(struct vatpit));
	vatpit->vm = vm;

	VATPIT_LOCK_INIT(vatpit)

	FREQ2BT(PIT_8254_FREQ, &bt);
	vatpit->freq_sbt = bttosbt(bt);

	for (i = 0; i < 3; i++) {
		callout_init(&vatpit->channel[i].callout, true);
		arg = &vatpit->channel[i].callout_arg;
		arg->vatpit = vatpit;
		arg->channel_num = i;
	}

	return (vatpit);
}

void
vatpit_cleanup(struct vatpit *vatpit)
{
	int i;

	for (i = 0; i < 3; i++)
		callout_drain(&vatpit->channel[i].callout);

	free(vatpit);
}
