// SPDX-License-Identifier: GPL-2.0
/*
 * Finite state machine for vfio-ccw device handling
 *
 * Copyright IBM Corp. 2017
 * Copyright Red Hat, Inc. 2019
 *
 * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
 *            Cornelia Huck <cohuck@redhat.com>
 */

#include <linux/vfio.h>

#include <asm/isc.h>

#include "ioasm.h"
#include "vfio_ccw_private.h"

static int fsm_io_helper(struct vfio_ccw_private *private)
{
        struct subchannel *sch = to_subchannel(private->vdev.dev->parent);
        union orb *orb;
        int ccode;
        __u8 lpm;
        unsigned long flags;
        int ret;

        spin_lock_irqsave(&sch->lock, flags);

        orb = cp_get_orb(&private->cp, sch);
        if (!orb) {
                ret = -EIO;
                goto out;
        }

        VFIO_CCW_TRACE_EVENT(5, "stIO");
        VFIO_CCW_TRACE_EVENT(5, dev_name(&sch->dev));

        /* Issue "Start Subchannel" */
        ccode = ssch(sch->schid, orb);

        VFIO_CCW_HEX_EVENT(5, &ccode, sizeof(ccode));

        switch (ccode) {
        case 0:
                /*
                 * Initialize device status information
                 */
                sch->schib.scsw.cmd.actl |= SCSW_ACTL_START_PEND;
                ret = 0;
                private->state = VFIO_CCW_STATE_CP_PENDING;
                break;
        case 1:         /* Status pending */
        case 2:         /* Busy */
                ret = -EBUSY;
                break;
        case 3:         /* Device/path not operational */
        {
                lpm = orb->cmd.lpm;
                if (lpm != 0)
                        sch->lpm &= ~lpm;
                else
                        sch->lpm = 0;

                if (cio_update_schib(sch))
                        ret = -ENODEV;
                else
                        ret = sch->lpm ? -EACCES : -ENODEV;
                break;
        }
        default:
                ret = ccode;
        }
out:
        spin_unlock_irqrestore(&sch->lock, flags);
        return ret;
}

static int fsm_do_halt(struct vfio_ccw_private *private)
{
        struct subchannel *sch = to_subchannel(private->vdev.dev->parent);
        unsigned long flags;
        int ccode;
        int ret;

        spin_lock_irqsave(&sch->lock, flags);

        VFIO_CCW_TRACE_EVENT(2, "haltIO");
        VFIO_CCW_TRACE_EVENT(2, dev_name(&sch->dev));

        /* Issue "Halt Subchannel" */
        ccode = hsch(sch->schid);

        VFIO_CCW_HEX_EVENT(2, &ccode, sizeof(ccode));

        switch (ccode) {
        case 0:
                /*
                 * Initialize device status information
                 */
                sch->schib.scsw.cmd.actl |= SCSW_ACTL_HALT_PEND;
                ret = 0;
                break;
        case 1:         /* Status pending */
        case 2:         /* Busy */
                ret = -EBUSY;
                break;
        case 3:         /* Device not operational */
                ret = -ENODEV;
                break;
        default:
                ret = ccode;
        }
        spin_unlock_irqrestore(&sch->lock, flags);
        return ret;
}

static int fsm_do_clear(struct vfio_ccw_private *private)
{
        struct subchannel *sch = to_subchannel(private->vdev.dev->parent);
        unsigned long flags;
        int ccode;
        int ret;

        spin_lock_irqsave(&sch->lock, flags);

        VFIO_CCW_TRACE_EVENT(2, "clearIO");
        VFIO_CCW_TRACE_EVENT(2, dev_name(&sch->dev));

        /* Issue "Clear Subchannel" */
        ccode = csch(sch->schid);

        VFIO_CCW_HEX_EVENT(2, &ccode, sizeof(ccode));

        switch (ccode) {
        case 0:
                /*
                 * Initialize device status information
                 */
                sch->schib.scsw.cmd.actl = SCSW_ACTL_CLEAR_PEND;
                /* TODO: check what else we might need to clear */
                ret = 0;
                break;
        case 3:         /* Device not operational */
                ret = -ENODEV;
                break;
        default:
                ret = ccode;
        }
        spin_unlock_irqrestore(&sch->lock, flags);
        return ret;
}

static void fsm_notoper(struct vfio_ccw_private *private,
                        enum vfio_ccw_event event)
{
        struct subchannel *sch = to_subchannel(private->vdev.dev->parent);

        VFIO_CCW_MSG_EVENT(2, "sch %x.%x.%04x: notoper event %x state %x\n",
                           sch->schid.cssid,
                           sch->schid.ssid,
                           sch->schid.sch_no,
                           event,
                           private->state);

        /*
         * TODO:
         * Probably we should send the machine check to the guest.
         */
        css_sched_sch_todo(sch, SCH_TODO_UNREG);
        private->state = VFIO_CCW_STATE_NOT_OPER;

        /* This is usually handled during CLOSE event */
        cp_free(&private->cp);
}

/*
 * No operation action.
 */
static void fsm_nop(struct vfio_ccw_private *private,
                    enum vfio_ccw_event event)
{
}

static void fsm_io_error(struct vfio_ccw_private *private,
                         enum vfio_ccw_event event)
{
        pr_err("vfio-ccw: FSM: I/O request from state:%d\n", private->state);
        private->io_region->ret_code = -EIO;
}

static void fsm_io_busy(struct vfio_ccw_private *private,
                        enum vfio_ccw_event event)
{
        private->io_region->ret_code = -EBUSY;
}

static void fsm_io_retry(struct vfio_ccw_private *private,
                         enum vfio_ccw_event event)
{
        private->io_region->ret_code = -EAGAIN;
}

static void fsm_async_error(struct vfio_ccw_private *private,
                            enum vfio_ccw_event event)
{
        struct ccw_cmd_region *cmd_region = private->cmd_region;

        pr_err("vfio-ccw: FSM: %s request from state:%d\n",
               cmd_region->command == VFIO_CCW_ASYNC_CMD_HSCH ? "halt" :
               cmd_region->command == VFIO_CCW_ASYNC_CMD_CSCH ? "clear" :
               "<unknown>", private->state);
        cmd_region->ret_code = -EIO;
}

static void fsm_async_retry(struct vfio_ccw_private *private,
                            enum vfio_ccw_event event)
{
        private->cmd_region->ret_code = -EAGAIN;
}

static void fsm_disabled_irq(struct vfio_ccw_private *private,
                             enum vfio_ccw_event event)
{
        struct subchannel *sch = to_subchannel(private->vdev.dev->parent);

        /*
         * An interrupt in a disabled state means a previous disable was not
         * successful - should not happen, but we try to disable again.
         */
        cio_disable_subchannel(sch);
}
inline struct subchannel_id get_schid(struct vfio_ccw_private *p)
{
        struct subchannel *sch = to_subchannel(p->vdev.dev->parent);

        return sch->schid;
}

/*
 * Deal with the ccw command request from the userspace.
 */
static void fsm_io_request(struct vfio_ccw_private *private,
                           enum vfio_ccw_event event)
{
        union orb *orb;
        union scsw *scsw = &private->scsw;
        struct ccw_io_region *io_region = private->io_region;
        char *errstr = "request";
        struct subchannel_id schid = get_schid(private);

        private->state = VFIO_CCW_STATE_CP_PROCESSING;
        memcpy(scsw, io_region->scsw_area, sizeof(*scsw));

        if (scsw->cmd.fctl & SCSW_FCTL_START_FUNC) {
                orb = (union orb *)io_region->orb_area;

                /* Don't try to build a cp if transport mode is specified. */
                if (orb->tm.b) {
                        io_region->ret_code = -EOPNOTSUPP;
                        VFIO_CCW_MSG_EVENT(2,
                                           "sch %x.%x.%04x: transport mode\n",
                                           schid.cssid,
                                           schid.ssid, schid.sch_no);
                        errstr = "transport mode";
                        goto err_out;
                }
                io_region->ret_code = cp_init(&private->cp, orb);
                if (io_region->ret_code) {
                        VFIO_CCW_MSG_EVENT(2,
                                           "sch %x.%x.%04x: cp_init=%d\n",
                                           schid.cssid,
                                           schid.ssid, schid.sch_no,
                                           io_region->ret_code);
                        errstr = "cp init";
                        goto err_out;
                }

                io_region->ret_code = cp_prefetch(&private->cp);
                if (io_region->ret_code) {
                        VFIO_CCW_MSG_EVENT(2,
                                           "sch %x.%x.%04x: cp_prefetch=%d\n",
                                           schid.cssid,
                                           schid.ssid, schid.sch_no,
                                           io_region->ret_code);
                        errstr = "cp prefetch";
                        cp_free(&private->cp);
                        goto err_out;
                }

                /* Start channel program and wait for I/O interrupt. */
                io_region->ret_code = fsm_io_helper(private);
                if (io_region->ret_code) {
                        VFIO_CCW_MSG_EVENT(2,
                                           "sch %x.%x.%04x: fsm_io_helper=%d\n",
                                           schid.cssid,
                                           schid.ssid, schid.sch_no,
                                           io_region->ret_code);
                        errstr = "cp fsm_io_helper";
                        cp_free(&private->cp);
                        goto err_out;
                }
                return;
        } else if (scsw->cmd.fctl & SCSW_FCTL_HALT_FUNC) {
                VFIO_CCW_MSG_EVENT(2,
                                   "sch %x.%x.%04x: halt on io_region\n",
                                   schid.cssid,
                                   schid.ssid, schid.sch_no);
                /* halt is handled via the async cmd region */
                io_region->ret_code = -EOPNOTSUPP;
                goto err_out;
        } else if (scsw->cmd.fctl & SCSW_FCTL_CLEAR_FUNC) {
                VFIO_CCW_MSG_EVENT(2,
                                   "sch %x.%x.%04x: clear on io_region\n",
                                   schid.cssid,
                                   schid.ssid, schid.sch_no);
                /* clear is handled via the async cmd region */
                io_region->ret_code = -EOPNOTSUPP;
                goto err_out;
        }

err_out:
        private->state = VFIO_CCW_STATE_IDLE;
        trace_vfio_ccw_fsm_io_request(scsw->cmd.fctl, schid,
                                      io_region->ret_code, errstr);
}

/*
 * Deal with an async request from userspace.
 */
static void fsm_async_request(struct vfio_ccw_private *private,
                              enum vfio_ccw_event event)
{
        struct ccw_cmd_region *cmd_region = private->cmd_region;

        switch (cmd_region->command) {
        case VFIO_CCW_ASYNC_CMD_HSCH:
                cmd_region->ret_code = fsm_do_halt(private);
                break;
        case VFIO_CCW_ASYNC_CMD_CSCH:
                cmd_region->ret_code = fsm_do_clear(private);
                break;
        default:
                /* should not happen? */
                cmd_region->ret_code = -EINVAL;
        }

        trace_vfio_ccw_fsm_async_request(get_schid(private),
                                         cmd_region->command,
                                         cmd_region->ret_code);
}

/*
 * Got an interrupt for a normal io (state busy).
 */
static void fsm_irq(struct vfio_ccw_private *private,
                    enum vfio_ccw_event event)
{
        struct subchannel *sch = to_subchannel(private->vdev.dev->parent);
        struct irb *irb = this_cpu_ptr(&cio_irb);

        VFIO_CCW_TRACE_EVENT(6, "IRQ");
        VFIO_CCW_TRACE_EVENT(6, dev_name(&sch->dev));

        memcpy(&private->irb, irb, sizeof(*irb));

        queue_work(vfio_ccw_work_q, &private->io_work);

        if (private->completion)
                complete(private->completion);
}

static void fsm_open(struct vfio_ccw_private *private,
                     enum vfio_ccw_event event)
{
        struct subchannel *sch = to_subchannel(private->vdev.dev->parent);
        int ret;

        spin_lock_irq(&sch->lock);
        sch->isc = VFIO_CCW_ISC;
        ret = cio_enable_subchannel(sch, (u32)virt_to_phys(sch));
        if (ret)
                goto err_unlock;

        private->state = VFIO_CCW_STATE_IDLE;
        spin_unlock_irq(&sch->lock);
        return;

err_unlock:
        spin_unlock_irq(&sch->lock);
        vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
}

static void fsm_close(struct vfio_ccw_private *private,
                      enum vfio_ccw_event event)
{
        struct subchannel *sch = to_subchannel(private->vdev.dev->parent);
        int ret;

        spin_lock_irq(&sch->lock);

        if (!sch->schib.pmcw.ena)
                goto err_unlock;

        ret = cio_disable_subchannel(sch);
        if (ret == -EBUSY)
                ret = vfio_ccw_sch_quiesce(sch);
        if (ret)
                goto err_unlock;

        private->state = VFIO_CCW_STATE_STANDBY;
        spin_unlock_irq(&sch->lock);
        cp_free(&private->cp);
        return;

err_unlock:
        spin_unlock_irq(&sch->lock);
        vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
}

/*
 * Device statemachine
 */
fsm_func_t *vfio_ccw_jumptable[NR_VFIO_CCW_STATES][NR_VFIO_CCW_EVENTS] = {
        [VFIO_CCW_STATE_NOT_OPER] = {
                [VFIO_CCW_EVENT_NOT_OPER]       = fsm_nop,
                [VFIO_CCW_EVENT_IO_REQ]         = fsm_io_error,
                [VFIO_CCW_EVENT_ASYNC_REQ]      = fsm_async_error,
                [VFIO_CCW_EVENT_INTERRUPT]      = fsm_disabled_irq,
                [VFIO_CCW_EVENT_OPEN]           = fsm_nop,
                [VFIO_CCW_EVENT_CLOSE]          = fsm_nop,
        },
        [VFIO_CCW_STATE_STANDBY] = {
                [VFIO_CCW_EVENT_NOT_OPER]       = fsm_notoper,
                [VFIO_CCW_EVENT_IO_REQ]         = fsm_io_error,
                [VFIO_CCW_EVENT_ASYNC_REQ]      = fsm_async_error,
                [VFIO_CCW_EVENT_INTERRUPT]      = fsm_disabled_irq,
                [VFIO_CCW_EVENT_OPEN]           = fsm_open,
                [VFIO_CCW_EVENT_CLOSE]          = fsm_notoper,
        },
        [VFIO_CCW_STATE_IDLE] = {
                [VFIO_CCW_EVENT_NOT_OPER]       = fsm_notoper,
                [VFIO_CCW_EVENT_IO_REQ]         = fsm_io_request,
                [VFIO_CCW_EVENT_ASYNC_REQ]      = fsm_async_request,
                [VFIO_CCW_EVENT_INTERRUPT]      = fsm_irq,
                [VFIO_CCW_EVENT_OPEN]           = fsm_notoper,
                [VFIO_CCW_EVENT_CLOSE]          = fsm_close,
        },
        [VFIO_CCW_STATE_CP_PROCESSING] = {
                [VFIO_CCW_EVENT_NOT_OPER]       = fsm_notoper,
                [VFIO_CCW_EVENT_IO_REQ]         = fsm_io_retry,
                [VFIO_CCW_EVENT_ASYNC_REQ]      = fsm_async_retry,
                [VFIO_CCW_EVENT_INTERRUPT]      = fsm_irq,
                [VFIO_CCW_EVENT_OPEN]           = fsm_notoper,
                [VFIO_CCW_EVENT_CLOSE]          = fsm_close,
        },
        [VFIO_CCW_STATE_CP_PENDING] = {
                [VFIO_CCW_EVENT_NOT_OPER]       = fsm_notoper,
                [VFIO_CCW_EVENT_IO_REQ]         = fsm_io_busy,
                [VFIO_CCW_EVENT_ASYNC_REQ]      = fsm_async_request,
                [VFIO_CCW_EVENT_INTERRUPT]      = fsm_irq,
                [VFIO_CCW_EVENT_OPEN]           = fsm_notoper,
                [VFIO_CCW_EVENT_CLOSE]          = fsm_close,
        },
};