/*
 * Finite state machine for vfio-ccw device handling
 *
 * Copyright IBM Corp. 2017
 *
 * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
 */

#include <linux/vfio.h>
#include <linux/mdev.h>

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

static int fsm_io_helper(struct vfio_ccw_private *private)
{
	struct subchannel *sch;
	union orb *orb;
	int ccode;
	__u8 lpm;
	unsigned long flags;

	sch = private->sch;

	spin_lock_irqsave(sch->lock, flags);
	private->state = VFIO_CCW_STATE_BUSY;
	spin_unlock_irqrestore(sch->lock, flags);

	orb = cp_get_orb(&private->cp, (u32)(addr_t)sch, sch->lpm);

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

	switch (ccode) {
	case 0:
		/*
		 * Initialize device status information
		 */
		sch->schib.scsw.cmd.actl |= SCSW_ACTL_START_PEND;
		return 0;
	case 1:		/* Status pending */
	case 2:		/* Busy */
		return -EBUSY;
	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))
			return -ENODEV;

		return sch->lpm ? -EACCES : -ENODEV;
	}
	default:
		return ccode;
	}
}

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

	/*
	 * 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;
}

/*
 * 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_disabled_irq(struct vfio_ccw_private *private,
			     enum vfio_ccw_event event)
{
	struct subchannel *sch = private->sch;

	/*
	 * 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);
}

/*
 * 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;
	struct mdev_device *mdev = private->mdev;

	private->state = VFIO_CCW_STATE_BOXED;

	memcpy(scsw, io_region->scsw_area, sizeof(*scsw));

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

		io_region->ret_code = cp_init(&private->cp, mdev_dev(mdev),
					      orb);
		if (io_region->ret_code)
			goto err_out;

		io_region->ret_code = cp_prefetch(&private->cp);
		if (io_region->ret_code) {
			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) {
			cp_free(&private->cp);
			goto err_out;
		}
		return;
	} else if (scsw->cmd.fctl & SCSW_FCTL_HALT_FUNC) {
		/* XXX: Handle halt. */
		io_region->ret_code = -EOPNOTSUPP;
		goto err_out;
	} else if (scsw->cmd.fctl & SCSW_FCTL_CLEAR_FUNC) {
		/* XXX: Handle clear. */
		io_region->ret_code = -EOPNOTSUPP;
		goto err_out;
	}

err_out:
	private->state = VFIO_CCW_STATE_IDLE;
}

/*
 * Got an interrupt for a normal io (state busy).
 */
static void fsm_irq(struct vfio_ccw_private *private,
		    enum vfio_ccw_event event)
{
	struct irb *irb = this_cpu_ptr(&cio_irb);

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

	queue_work(vfio_ccw_work_q, &private->io_work);

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

/*
 * 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_INTERRUPT]	= fsm_disabled_irq,
	},
	[VFIO_CCW_STATE_STANDBY] = {
		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_error,
		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
	},
	[VFIO_CCW_STATE_IDLE] = {
		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_request,
		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
	},
	[VFIO_CCW_STATE_BOXED] = {
		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_busy,
		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
	},
	[VFIO_CCW_STATE_BUSY] = {
		[VFIO_CCW_EVENT_NOT_OPER]	= fsm_notoper,
		[VFIO_CCW_EVENT_IO_REQ]		= fsm_io_busy,
		[VFIO_CCW_EVENT_INTERRUPT]	= fsm_irq,
	},
};