/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2017 The FreeBSD Foundation
 *
 * 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.
 * 3. The name of the company nor the name of the author may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 THE AUTHOR 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 <sys/cdefs.h>
#include <sys/types.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/rman.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <sys/timeet.h>
#include <sys/timetc.h>

#include <machine/bus.h>
#include <machine/machdep.h>
#include <machine/vmm.h>

#include <arm64/vmm/arm64.h>

#include <dev/vmm/vmm_vm.h>

#include "vgic.h"
#include "vtimer.h"

#define RES1            0xffffffffffffffffUL

#define timer_enabled(ctl)      \
    (!((ctl) & CNTP_CTL_IMASK) && ((ctl) & CNTP_CTL_ENABLE))

static uint32_t tmr_frq;

#define timer_condition_met(ctl)        ((ctl) & CNTP_CTL_ISTATUS)

SYSCTL_DECL(_hw_vmm);
SYSCTL_NODE(_hw_vmm, OID_AUTO, vtimer, CTLFLAG_RW, NULL, NULL);

static bool allow_ecv_phys = false;
SYSCTL_BOOL(_hw_vmm_vtimer, OID_AUTO, allow_ecv_phys, CTLFLAG_RW,
    &allow_ecv_phys, 0,
    "Enable hardware access to the physical timer if FEAT_ECV_POFF is supported");

static void vtimer_schedule_irq(struct hypctx *hypctx, bool phys);

static int
vtimer_virtual_timer_intr(void *arg)
{
        struct hypctx *hypctx;
        uint64_t cntpct_el0;
        uint32_t cntv_ctl;

        hypctx = arm64_get_active_vcpu();
        cntv_ctl = READ_SPECIALREG(cntv_ctl_el0);

        if (!hypctx) {
                /* vm_destroy() was called. */
                eprintf("No active vcpu\n");
                cntv_ctl = READ_SPECIALREG(cntv_ctl_el0);
                goto out;
        }
        if (!timer_enabled(cntv_ctl)) {
                eprintf("Timer not enabled\n");
                goto out;
        }
        if (!timer_condition_met(cntv_ctl)) {
                eprintf("Timer condition not met\n");
                goto out;
        }

        cntpct_el0 = READ_SPECIALREG(cntpct_el0) -
            hypctx->hyp->vtimer.cntvoff_el2;
        if (hypctx->vtimer_cpu.virt_timer.cntx_cval_el0 < cntpct_el0)
                vgic_inject_irq(hypctx->hyp, vcpu_vcpuid(hypctx->vcpu),
                    GT_VIRT_IRQ, true);

        cntv_ctl = hypctx->vtimer_cpu.virt_timer.cntx_ctl_el0;

out:
        /*
         * Disable the timer interrupt. This will prevent the interrupt from
         * being reasserted as soon as we exit the handler and getting stuck
         * in an infinite loop.
         *
         * This is safe to do because the guest disabled the timer, and then
         * enables it as part of the interrupt handling routine.
         */
        cntv_ctl &= ~CNTP_CTL_ENABLE;
        WRITE_SPECIALREG(cntv_ctl_el0, cntv_ctl);

        return (FILTER_HANDLED);
}

int
vtimer_init(void)
{
        /*
         * The guest *MUST* use the same timer frequency as the host. The
         * register CNTFRQ_EL0 is accessible to the guest and a different value
         * in the guest dts file might have unforseen consequences.
         */
        tmr_frq = READ_SPECIALREG(cntfrq_el0);

        return (0);
}

void
vtimer_vminit(struct hyp *hyp)
{
        uint64_t now;
        bool ecv_poff;

        ecv_poff = false;

        if (allow_ecv_phys && (hyp->feats & HYP_FEAT_ECV_POFF) != 0)
                ecv_poff = true;

        /*
         * Configure the Counter-timer Hypervisor Control Register for the VM.
         */
        if (in_vhe()) {
                /*
                 * CNTHCTL_E2H_EL0PCTEN: trap EL0 access to CNTP{CT,CTSS}_EL0
                 * CNTHCTL_E2H_EL0VCTEN: don't trap EL0 access to
                 *                      CNTV{CT,CTXX}_EL0
                 * CNTHCTL_E2H_EL0VTEN: don't trap EL0 access to
                 *                      CNTV_{CTL,CVAL,TVAL}_EL0
                 * CNTHCTL_E2H_EL0PTEN: trap EL0 access to
                 *                      CNTP_{CTL,CVAL,TVAL}_EL0
                 * CNTHCTL_E2H_EL1PCTEN: trap access to CNTPCT_EL0
                 * CNTHCTL_E2H_EL1PTEN: trap access to
                 *                      CNTP_{CTL,CVAL,TVAL}_EL0
                 * CNTHCTL_E2H_EL1VCTEN: don't trap EL0 access to
                 *                       CNTV{CT,CTSS}_EL0
                 * CNTHCTL_E2H_EL1PCEN: trap EL1 access to
                 *                      CNTP_{CTL,CVAL,TVAL}_EL0
                 *
                 * TODO: Don't trap when FEAT_ECV is present
                 */
                hyp->vtimer.cnthctl_el2 =
                    CNTHCTL_E2H_EL0VCTEN_NOTRAP |
                    CNTHCTL_E2H_EL0VTEN_NOTRAP;
                if (ecv_poff) {
                        hyp->vtimer.cnthctl_el2 |=
                            CNTHCTL_E2H_EL0PCTEN_NOTRAP |
                            CNTHCTL_E2H_EL0PTEN_NOTRAP |
                            CNTHCTL_E2H_EL1PCTEN_NOTRAP |
                            CNTHCTL_E2H_EL1PTEN_NOTRAP;
                } else {
                        hyp->vtimer.cnthctl_el2 |=
                            CNTHCTL_E2H_EL0PCTEN_TRAP |
                            CNTHCTL_E2H_EL0PTEN_TRAP |
                            CNTHCTL_E2H_EL1PCTEN_TRAP |
                            CNTHCTL_E2H_EL1PTEN_TRAP;
                }
        } else {
                /*
                 * CNTHCTL_EL1PCEN: trap access to CNTP_{CTL, CVAL, TVAL}_EL0
                 *                  from EL1
                 * CNTHCTL_EL1PCTEN: trap access to CNTPCT_EL0
                 */
                if (ecv_poff) {
                        hyp->vtimer.cnthctl_el2 =
                            CNTHCTL_EL1PCTEN_NOTRAP |
                            CNTHCTL_EL1PCEN_NOTRAP;
                } else {
                        hyp->vtimer.cnthctl_el2 =
                            CNTHCTL_EL1PCTEN_TRAP |
                            CNTHCTL_EL1PCEN_TRAP;
                }
        }

        if (ecv_poff)
                hyp->vtimer.cnthctl_el2 |= CNTHCTL_ECV_EN;

        now = READ_SPECIALREG(cntpct_el0);
        hyp->vtimer.cntvoff_el2 = now;

        return;
}

void
vtimer_cpuinit(struct hypctx *hypctx)
{
        struct vtimer_cpu *vtimer_cpu;

        vtimer_cpu = &hypctx->vtimer_cpu;
        /*
         * Configure physical timer interrupts for the VCPU.
         *
         * CNTP_CTL_IMASK: mask interrupts
         * ~CNTP_CTL_ENABLE: disable the timer
         */
        vtimer_cpu->phys_timer.cntx_ctl_el0 = CNTP_CTL_IMASK & ~CNTP_CTL_ENABLE;

        mtx_init(&vtimer_cpu->phys_timer.mtx, "vtimer phys callout mutex", NULL,
            MTX_DEF);
        callout_init_mtx(&vtimer_cpu->phys_timer.callout,
            &vtimer_cpu->phys_timer.mtx, 0);
        vtimer_cpu->phys_timer.irqid = GT_PHYS_NS_IRQ;

        mtx_init(&vtimer_cpu->virt_timer.mtx, "vtimer virt callout mutex", NULL,
            MTX_DEF);
        callout_init_mtx(&vtimer_cpu->virt_timer.callout,
            &vtimer_cpu->virt_timer.mtx, 0);
        vtimer_cpu->virt_timer.irqid = GT_VIRT_IRQ;
}

void
vtimer_cpucleanup(struct hypctx *hypctx)
{
        struct vtimer_cpu *vtimer_cpu;

        vtimer_cpu = &hypctx->vtimer_cpu;
        callout_drain(&vtimer_cpu->phys_timer.callout);
        callout_drain(&vtimer_cpu->virt_timer.callout);
        mtx_destroy(&vtimer_cpu->phys_timer.mtx);
        mtx_destroy(&vtimer_cpu->virt_timer.mtx);
}

void
vtimer_vmcleanup(struct hyp *hyp)
{
        struct hypctx *hypctx;
        uint32_t cntv_ctl;

        hypctx = arm64_get_active_vcpu();
        if (!hypctx) {
                /* The active VM was destroyed, stop the timer. */
                cntv_ctl = READ_SPECIALREG(cntv_ctl_el0);
                cntv_ctl &= ~CNTP_CTL_ENABLE;
                WRITE_SPECIALREG(cntv_ctl_el0, cntv_ctl);
        }
}

void
vtimer_cleanup(void)
{
}

static void
vtime_sync_timer(struct hypctx *hypctx, struct vtimer_timer *timer,
    uint64_t cntpct_el0)
{
        if (!timer_enabled(timer->cntx_ctl_el0)) {
                vgic_inject_irq(hypctx->hyp, vcpu_vcpuid(hypctx->vcpu),
                    timer->irqid, false);
        } else if (timer->cntx_cval_el0 < cntpct_el0) {
                vgic_inject_irq(hypctx->hyp, vcpu_vcpuid(hypctx->vcpu),
                    timer->irqid, true);
        } else {
                vgic_inject_irq(hypctx->hyp, vcpu_vcpuid(hypctx->vcpu),
                    timer->irqid, false);
                vtimer_schedule_irq(hypctx, false);
        }
}

void
vtimer_sync_hwstate(struct hypctx *hypctx)
{
        uint64_t cntpct_el0;

        cntpct_el0 = READ_SPECIALREG(cntpct_el0) -
            hypctx->hyp->vtimer.cntvoff_el2;
        vtime_sync_timer(hypctx, &hypctx->vtimer_cpu.virt_timer, cntpct_el0);
        /* If FEAT_ECV_POFF is in use then we need to sync the physical timer */
        if ((hypctx->hyp->vtimer.cnthctl_el2 & CNTHCTL_ECV_EN) != 0) {
                vtime_sync_timer(hypctx, &hypctx->vtimer_cpu.phys_timer,
                    cntpct_el0);
        }
}

static void
vtimer_inject_irq_callout_phys(void *context)
{
        struct hypctx *hypctx;

        hypctx = context;
        vgic_inject_irq(hypctx->hyp, vcpu_vcpuid(hypctx->vcpu),
            hypctx->vtimer_cpu.phys_timer.irqid, true);
}

static void
vtimer_inject_irq_callout_virt(void *context)
{
        struct hypctx *hypctx;

        hypctx = context;
        vgic_inject_irq(hypctx->hyp, vcpu_vcpuid(hypctx->vcpu),
            hypctx->vtimer_cpu.virt_timer.irqid, true);
}

static void
vtimer_schedule_irq(struct hypctx *hypctx, bool phys)
{
        sbintime_t time;
        struct vtimer_timer *timer;
        uint64_t cntpct_el0;
        uint64_t diff;

        if (phys)
                timer = &hypctx->vtimer_cpu.phys_timer;
        else
                timer = &hypctx->vtimer_cpu.virt_timer;
        cntpct_el0 = READ_SPECIALREG(cntpct_el0) -
            hypctx->hyp->vtimer.cntvoff_el2;
        if (timer->cntx_cval_el0 < cntpct_el0) {
                /* Timer set in the past, trigger interrupt */
                vgic_inject_irq(hypctx->hyp, vcpu_vcpuid(hypctx->vcpu),
                    timer->irqid, true);
        } else {
                diff = timer->cntx_cval_el0 - cntpct_el0;
                time = diff * SBT_1S / tmr_frq;
                if (phys)
                        callout_reset_sbt(&timer->callout, time, 0,
                            vtimer_inject_irq_callout_phys, hypctx, 0);
                else
                        callout_reset_sbt(&timer->callout, time, 0,
                            vtimer_inject_irq_callout_virt, hypctx, 0);
        }
}

static void
vtimer_remove_irq(struct hypctx *hypctx, struct vcpu *vcpu)
{
        struct vtimer_cpu *vtimer_cpu;
        struct vtimer_timer *timer;

        vtimer_cpu = &hypctx->vtimer_cpu;
        timer = &vtimer_cpu->phys_timer;

        callout_drain(&timer->callout);
        /*
         * The interrupt needs to be deactivated here regardless of the callout
         * function having been executed. The timer interrupt can be masked with
         * the CNTP_CTL_EL0.IMASK bit instead of reading the IAR register.
         * Masking the interrupt doesn't remove it from the list registers.
         */
        vgic_inject_irq(hypctx->hyp, vcpu_vcpuid(vcpu), timer->irqid, false);
}

/*
 * Timer emulation functions.
 *
 * The guest should use the virtual timer, however some software, e.g. u-boot,
 * used the physical timer. Emulate this in software for the guest to use.
 *
 * Adjust for cntvoff_el2 so the physical and virtual timers are at similar
 * times. This simplifies interrupt handling in the virtual timer as the
 * adjustment will have already happened.
 */

int
vtimer_phys_ctl_read(struct vcpu *vcpu, uint64_t *rval, void *arg)
{
        struct hyp *hyp;
        struct hypctx *hypctx;
        struct vtimer_cpu *vtimer_cpu;
        uint64_t cntpct_el0;

        hypctx = vcpu_get_cookie(vcpu);
        hyp = hypctx->hyp;
        vtimer_cpu = &hypctx->vtimer_cpu;

        cntpct_el0 = READ_SPECIALREG(cntpct_el0) - hyp->vtimer.cntvoff_el2;
        if (vtimer_cpu->phys_timer.cntx_cval_el0 < cntpct_el0)
                /* Timer condition met */
                *rval = vtimer_cpu->phys_timer.cntx_ctl_el0 | CNTP_CTL_ISTATUS;
        else
                *rval = vtimer_cpu->phys_timer.cntx_ctl_el0 & ~CNTP_CTL_ISTATUS;

        return (0);
}

int
vtimer_phys_ctl_write(struct vcpu *vcpu, uint64_t wval, void *arg)
{
        struct hypctx *hypctx;
        struct vtimer_cpu *vtimer_cpu;
        uint64_t ctl_el0;
        bool timer_toggled_on;

        hypctx = vcpu_get_cookie(vcpu);
        vtimer_cpu = &hypctx->vtimer_cpu;

        timer_toggled_on = false;
        ctl_el0 = vtimer_cpu->phys_timer.cntx_ctl_el0;

        if (!timer_enabled(ctl_el0) && timer_enabled(wval))
                timer_toggled_on = true;
        else if (timer_enabled(ctl_el0) && !timer_enabled(wval))
                vtimer_remove_irq(hypctx, vcpu);

        vtimer_cpu->phys_timer.cntx_ctl_el0 = wval;

        if (timer_toggled_on)
                vtimer_schedule_irq(hypctx, true);

        return (0);
}

int
vtimer_phys_cnt_read(struct vcpu *vcpu, uint64_t *rval, void *arg)
{
        struct vm *vm;
        struct hyp *hyp;

        vm = vcpu_vm(vcpu);
        hyp = vm_get_cookie(vm);
        *rval = READ_SPECIALREG(cntpct_el0) - hyp->vtimer.cntvoff_el2;
        return (0);
}

int
vtimer_phys_cnt_write(struct vcpu *vcpu, uint64_t wval, void *arg)
{
        return (0);
}

int
vtimer_phys_cval_read(struct vcpu *vcpu, uint64_t *rval, void *arg)
{
        struct hypctx *hypctx;
        struct vtimer_cpu *vtimer_cpu;

        hypctx = vcpu_get_cookie(vcpu);
        vtimer_cpu = &hypctx->vtimer_cpu;

        *rval = vtimer_cpu->phys_timer.cntx_cval_el0;

        return (0);
}

int
vtimer_phys_cval_write(struct vcpu *vcpu, uint64_t wval, void *arg)
{
        struct hypctx *hypctx;
        struct vtimer_cpu *vtimer_cpu;

        hypctx = vcpu_get_cookie(vcpu);
        vtimer_cpu = &hypctx->vtimer_cpu;

        vtimer_cpu->phys_timer.cntx_cval_el0 = wval;

        vtimer_remove_irq(hypctx, vcpu);
        if (timer_enabled(vtimer_cpu->phys_timer.cntx_ctl_el0)) {
                vtimer_schedule_irq(hypctx, true);
        }

        return (0);
}

int
vtimer_phys_tval_read(struct vcpu *vcpu, uint64_t *rval, void *arg)
{
        struct hyp *hyp;
        struct hypctx *hypctx;
        struct vtimer_cpu *vtimer_cpu;
        uint32_t cntpct_el0;

        hypctx = vcpu_get_cookie(vcpu);
        hyp = hypctx->hyp;
        vtimer_cpu = &hypctx->vtimer_cpu;

        if (!(vtimer_cpu->phys_timer.cntx_ctl_el0 & CNTP_CTL_ENABLE)) {
                /*
                 * ARMv8 Architecture Manual, p. D7-2702: the result of reading
                 * TVAL when the timer is disabled is UNKNOWN. I have chosen to
                 * return the maximum value possible on 32 bits which means the
                 * timer will fire very far into the future.
                 */
                *rval = (uint32_t)RES1;
        } else {
                cntpct_el0 = READ_SPECIALREG(cntpct_el0) -
                    hyp->vtimer.cntvoff_el2;
                *rval = vtimer_cpu->phys_timer.cntx_cval_el0 - cntpct_el0;
        }

        return (0);
}

int
vtimer_phys_tval_write(struct vcpu *vcpu, uint64_t wval, void *arg)
{
        struct hyp *hyp;
        struct hypctx *hypctx;
        struct vtimer_cpu *vtimer_cpu;
        uint64_t cntpct_el0;

        hypctx = vcpu_get_cookie(vcpu);
        hyp = hypctx->hyp;
        vtimer_cpu = &hypctx->vtimer_cpu;

        cntpct_el0 = READ_SPECIALREG(cntpct_el0) - hyp->vtimer.cntvoff_el2;
        vtimer_cpu->phys_timer.cntx_cval_el0 = (int32_t)wval + cntpct_el0;

        vtimer_remove_irq(hypctx, vcpu);
        if (timer_enabled(vtimer_cpu->phys_timer.cntx_ctl_el0)) {
                vtimer_schedule_irq(hypctx, true);
        }

        return (0);
}

struct vtimer_softc {
        struct resource *res;
        void *ihl;
        int rid;
};

static int
vtimer_probe(device_t dev)
{
        device_set_desc(dev, "Virtual timer");
        return (BUS_PROBE_DEFAULT);
}

static int
vtimer_attach(device_t dev)
{
        struct vtimer_softc *sc;

        sc = device_get_softc(dev);

        sc->rid = 0;
        sc->res = bus_alloc_resource_any(dev, SYS_RES_IRQ, &sc->rid, RF_ACTIVE);
        if (sc->res == NULL)
                return (ENXIO);

        bus_setup_intr(dev, sc->res, INTR_TYPE_CLK, vtimer_virtual_timer_intr,
            NULL, NULL, &sc->ihl);

        return (0);
}

static device_method_t vtimer_methods[] = {
        /* Device interface */
        DEVMETHOD(device_probe,         vtimer_probe),
        DEVMETHOD(device_attach,        vtimer_attach),

        /* End */
        DEVMETHOD_END
};

DEFINE_CLASS_0(vtimer, vtimer_driver, vtimer_methods,
    sizeof(struct vtimer_softc));

DRIVER_MODULE(vtimer, generic_timer, vtimer_driver, 0, 0);