// SPDX-License-Identifier: GPL-2.0
/*
 * VFIO based Physical Subchannel device driver
 *
 * Copyright IBM Corp. 2017
 *
 * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
 *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/uuid.h>
#include <linux/mdev.h>

#include <asm/isc.h>

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

struct workqueue_struct *vfio_ccw_work_q;

/*
 * Helpers
 */
int vfio_ccw_sch_quiesce(struct subchannel *sch)
{
        struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
        DECLARE_COMPLETION_ONSTACK(completion);
        int iretry, ret = 0;

        spin_lock_irq(sch->lock);
        if (!sch->schib.pmcw.ena)
                goto out_unlock;
        ret = cio_disable_subchannel(sch);
        if (ret != -EBUSY)
                goto out_unlock;

        do {
                iretry = 255;

                ret = cio_cancel_halt_clear(sch, &iretry);
                while (ret == -EBUSY) {
                        /*
                         * Flush all I/O and wait for
                         * cancel/halt/clear completion.
                         */
                        private->completion = &completion;
                        spin_unlock_irq(sch->lock);

                        wait_for_completion_timeout(&completion, 3*HZ);

                        spin_lock_irq(sch->lock);
                        private->completion = NULL;
                        flush_workqueue(vfio_ccw_work_q);
                        ret = cio_cancel_halt_clear(sch, &iretry);
                };

                ret = cio_disable_subchannel(sch);
        } while (ret == -EBUSY);
out_unlock:
        private->state = VFIO_CCW_STATE_NOT_OPER;
        spin_unlock_irq(sch->lock);
        return ret;
}

static void vfio_ccw_sch_io_todo(struct work_struct *work)
{
        struct vfio_ccw_private *private;
        struct irb *irb;

        private = container_of(work, struct vfio_ccw_private, io_work);
        irb = &private->irb;

        if (scsw_is_solicited(&irb->scsw)) {
                cp_update_scsw(&private->cp, &irb->scsw);
                cp_free(&private->cp);
        }
        memcpy(private->io_region.irb_area, irb, sizeof(*irb));

        if (private->io_trigger)
                eventfd_signal(private->io_trigger, 1);

        if (private->mdev)
                private->state = VFIO_CCW_STATE_IDLE;
}

/*
 * Css driver callbacks
 */
static void vfio_ccw_sch_irq(struct subchannel *sch)
{
        struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);

        inc_irq_stat(IRQIO_CIO);
        vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_INTERRUPT);
}

static int vfio_ccw_sch_probe(struct subchannel *sch)
{
        struct pmcw *pmcw = &sch->schib.pmcw;
        struct vfio_ccw_private *private;
        int ret;

        if (pmcw->qf) {
                dev_warn(&sch->dev, "vfio: ccw: does not support QDIO: %s\n",
                         dev_name(&sch->dev));
                return -ENODEV;
        }

        private = kzalloc(sizeof(*private), GFP_KERNEL | GFP_DMA);
        if (!private)
                return -ENOMEM;
        private->sch = sch;
        dev_set_drvdata(&sch->dev, private);

        spin_lock_irq(sch->lock);
        private->state = VFIO_CCW_STATE_NOT_OPER;
        sch->isc = VFIO_CCW_ISC;
        ret = cio_enable_subchannel(sch, (u32)(unsigned long)sch);
        spin_unlock_irq(sch->lock);
        if (ret)
                goto out_free;

        ret = vfio_ccw_mdev_reg(sch);
        if (ret)
                goto out_disable;

        INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);
        atomic_set(&private->avail, 1);
        private->state = VFIO_CCW_STATE_STANDBY;

        return 0;

out_disable:
        cio_disable_subchannel(sch);
out_free:
        dev_set_drvdata(&sch->dev, NULL);
        kfree(private);
        return ret;
}

static int vfio_ccw_sch_remove(struct subchannel *sch)
{
        struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);

        vfio_ccw_sch_quiesce(sch);

        vfio_ccw_mdev_unreg(sch);

        dev_set_drvdata(&sch->dev, NULL);

        kfree(private);

        return 0;
}

static void vfio_ccw_sch_shutdown(struct subchannel *sch)
{
        vfio_ccw_sch_quiesce(sch);
}

/**
 * vfio_ccw_sch_event - process subchannel event
 * @sch: subchannel
 * @process: non-zero if function is called in process context
 *
 * An unspecified event occurred for this subchannel. Adjust data according
 * to the current operational state of the subchannel. Return zero when the
 * event has been handled sufficiently or -EAGAIN when this function should
 * be called again in process context.
 */
static int vfio_ccw_sch_event(struct subchannel *sch, int process)
{
        struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
        unsigned long flags;

        spin_lock_irqsave(sch->lock, flags);
        if (!device_is_registered(&sch->dev))
                goto out_unlock;

        if (work_pending(&sch->todo_work))
                goto out_unlock;

        if (cio_update_schib(sch)) {
                vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
                goto out_unlock;
        }

        private = dev_get_drvdata(&sch->dev);
        if (private->state == VFIO_CCW_STATE_NOT_OPER) {
                private->state = private->mdev ? VFIO_CCW_STATE_IDLE :
                                 VFIO_CCW_STATE_STANDBY;
        }

out_unlock:
        spin_unlock_irqrestore(sch->lock, flags);

        return 0;
}

static struct css_device_id vfio_ccw_sch_ids[] = {
        { .match_flags = 0x1, .type = SUBCHANNEL_TYPE_IO, },
        { /* end of list */ },
};
MODULE_DEVICE_TABLE(css, vfio_ccw_sch_ids);

static struct css_driver vfio_ccw_sch_driver = {
        .drv = {
                .name = "vfio_ccw",
                .owner = THIS_MODULE,
        },
        .subchannel_type = vfio_ccw_sch_ids,
        .irq = vfio_ccw_sch_irq,
        .probe = vfio_ccw_sch_probe,
        .remove = vfio_ccw_sch_remove,
        .shutdown = vfio_ccw_sch_shutdown,
        .sch_event = vfio_ccw_sch_event,
};

static int __init vfio_ccw_sch_init(void)
{
        int ret;

        vfio_ccw_work_q = create_singlethread_workqueue("vfio-ccw");
        if (!vfio_ccw_work_q)
                return -ENOMEM;

        isc_register(VFIO_CCW_ISC);
        ret = css_driver_register(&vfio_ccw_sch_driver);
        if (ret) {
                isc_unregister(VFIO_CCW_ISC);
                destroy_workqueue(vfio_ccw_work_q);
        }

        return ret;
}

static void __exit vfio_ccw_sch_exit(void)
{
        css_driver_unregister(&vfio_ccw_sch_driver);
        isc_unregister(VFIO_CCW_ISC);
        destroy_workqueue(vfio_ccw_work_q);
}
module_init(vfio_ccw_sch_init);
module_exit(vfio_ccw_sch_exit);

MODULE_LICENSE("GPL v2");