/*
 * Copyright 2014 IBM Corp.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/bitmap.h>
#include <linux/sched/signal.h>
#include <linux/poll.h>
#include <linux/pid.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/sched/mm.h>
#include <linux/mmu_context.h>
#include <asm/cputable.h>
#include <asm/current.h>
#include <asm/copro.h>

#include "cxl.h"
#include "trace.h"

#define CXL_NUM_MINORS 256 /* Total to reserve */

#define CXL_AFU_MINOR_D(afu) (CXL_CARD_MINOR(afu->adapter) + 1 + (3 * afu->slice))
#define CXL_AFU_MINOR_M(afu) (CXL_AFU_MINOR_D(afu) + 1)
#define CXL_AFU_MINOR_S(afu) (CXL_AFU_MINOR_D(afu) + 2)
#define CXL_AFU_MKDEV_D(afu) MKDEV(MAJOR(cxl_dev), CXL_AFU_MINOR_D(afu))
#define CXL_AFU_MKDEV_M(afu) MKDEV(MAJOR(cxl_dev), CXL_AFU_MINOR_M(afu))
#define CXL_AFU_MKDEV_S(afu) MKDEV(MAJOR(cxl_dev), CXL_AFU_MINOR_S(afu))

#define CXL_DEVT_AFU(dev) ((MINOR(dev) % CXL_DEV_MINORS - 1) / 3)

#define CXL_DEVT_IS_CARD(dev) (MINOR(dev) % CXL_DEV_MINORS == 0)

static dev_t cxl_dev;

static struct class *cxl_class;

static int __afu_open(struct inode *inode, struct file *file, bool master)
{
        struct cxl *adapter;
        struct cxl_afu *afu;
        struct cxl_context *ctx;
        int adapter_num = CXL_DEVT_ADAPTER(inode->i_rdev);
        int slice = CXL_DEVT_AFU(inode->i_rdev);
        int rc = -ENODEV;

        pr_devel("afu_open afu%i.%i\n", slice, adapter_num);

        if (!(adapter = get_cxl_adapter(adapter_num)))
                return -ENODEV;

        if (slice > adapter->slices)
                goto err_put_adapter;

        spin_lock(&adapter->afu_list_lock);
        if (!(afu = adapter->afu[slice])) {
                spin_unlock(&adapter->afu_list_lock);
                goto err_put_adapter;
        }

        /*
         * taking a ref to the afu so that it doesn't go away
         * for rest of the function. This ref is released before
         * we return.
         */
        cxl_afu_get(afu);
        spin_unlock(&adapter->afu_list_lock);

        if (!afu->current_mode)
                goto err_put_afu;

        if (!cxl_ops->link_ok(adapter, afu)) {
                rc = -EIO;
                goto err_put_afu;
        }

        if (!(ctx = cxl_context_alloc())) {
                rc = -ENOMEM;
                goto err_put_afu;
        }

        rc = cxl_context_init(ctx, afu, master);
        if (rc)
                goto err_put_afu;

        cxl_context_set_mapping(ctx, inode->i_mapping);

        pr_devel("afu_open pe: %i\n", ctx->pe);
        file->private_data = ctx;

        /* indicate success */
        rc = 0;

err_put_afu:
        /* release the ref taken earlier */
        cxl_afu_put(afu);
err_put_adapter:
        put_device(&adapter->dev);
        return rc;
}

int afu_open(struct inode *inode, struct file *file)
{
        return __afu_open(inode, file, false);
}

static int afu_master_open(struct inode *inode, struct file *file)
{
        return __afu_open(inode, file, true);
}

int afu_release(struct inode *inode, struct file *file)
{
        struct cxl_context *ctx = file->private_data;

        pr_devel("%s: closing cxl file descriptor. pe: %i\n",
                 __func__, ctx->pe);
        cxl_context_detach(ctx);


        /*
         * Delete the context's mapping pointer, unless it's created by the
         * kernel API, in which case leave it so it can be freed by reclaim_ctx()
         */
        if (!ctx->kernelapi) {
                mutex_lock(&ctx->mapping_lock);
                ctx->mapping = NULL;
                mutex_unlock(&ctx->mapping_lock);
        }

        /*
         * At this this point all bottom halfs have finished and we should be
         * getting no more IRQs from the hardware for this context.  Once it's
         * removed from the IDR (and RCU synchronised) it's safe to free the
         * sstp and context.
         */
        cxl_context_free(ctx);

        return 0;
}

static long afu_ioctl_start_work(struct cxl_context *ctx,
                                 struct cxl_ioctl_start_work __user *uwork)
{
        struct cxl_ioctl_start_work work;
        u64 amr = 0;
        int rc;

        pr_devel("%s: pe: %i\n", __func__, ctx->pe);

        /* Do this outside the status_mutex to avoid a circular dependency with
         * the locking in cxl_mmap_fault() */
        if (copy_from_user(&work, uwork, sizeof(work)))
                return -EFAULT;

        mutex_lock(&ctx->status_mutex);
        if (ctx->status != OPENED) {
                rc = -EIO;
                goto out;
        }

        /*
         * if any of the reserved fields are set or any of the unused
         * flags are set it's invalid
         */
        if (work.reserved1 || work.reserved2 || work.reserved3 ||
            work.reserved4 || work.reserved5 ||
            (work.flags & ~CXL_START_WORK_ALL)) {
                rc = -EINVAL;
                goto out;
        }

        if (!(work.flags & CXL_START_WORK_NUM_IRQS))
                work.num_interrupts = ctx->afu->pp_irqs;
        else if ((work.num_interrupts < ctx->afu->pp_irqs) ||
                 (work.num_interrupts > ctx->afu->irqs_max)) {
                rc =  -EINVAL;
                goto out;
        }

        if ((rc = afu_register_irqs(ctx, work.num_interrupts)))
                goto out;

        if (work.flags & CXL_START_WORK_AMR)
                amr = work.amr & mfspr(SPRN_UAMOR);

        if (work.flags & CXL_START_WORK_TID)
                ctx->assign_tidr = true;

        ctx->mmio_err_ff = !!(work.flags & CXL_START_WORK_ERR_FF);

        /*
         * Increment the mapped context count for adapter. This also checks
         * if adapter_context_lock is taken.
         */
        rc = cxl_adapter_context_get(ctx->afu->adapter);
        if (rc) {
                afu_release_irqs(ctx, ctx);
                goto out;
        }

        /*
         * We grab the PID here and not in the file open to allow for the case
         * where a process (master, some daemon, etc) has opened the chardev on
         * behalf of another process, so the AFU's mm gets bound to the process
         * that performs this ioctl and not the process that opened the file.
         * Also we grab the PID of the group leader so that if the task that
         * has performed the attach operation exits the mm context of the
         * process is still accessible.
         */
        ctx->pid = get_task_pid(current, PIDTYPE_PID);

        /* acquire a reference to the task's mm */
        ctx->mm = get_task_mm(current);

        /* ensure this mm_struct can't be freed */
        cxl_context_mm_count_get(ctx);

        if (ctx->mm) {
                /* decrement the use count from above */
                mmput(ctx->mm);
                /* make TLBIs for this context global */
                mm_context_add_copro(ctx->mm);
        }

        /*
         * Increment driver use count. Enables global TLBIs for hash
         * and callbacks to handle the segment table
         */
        cxl_ctx_get();

        /*
         * A barrier is needed to make sure all TLBIs are global
         * before we attach and the context starts being used by the
         * adapter.
         *
         * Needed after mm_context_add_copro() for radix and
         * cxl_ctx_get() for hash/p8.
         *
         * The barrier should really be mb(), since it involves a
         * device. However, it's only useful when we have local
         * vs. global TLBIs, i.e SMP=y. So keep smp_mb().
         */
        smp_mb();

        trace_cxl_attach(ctx, work.work_element_descriptor, work.num_interrupts, amr);

        if ((rc = cxl_ops->attach_process(ctx, false, work.work_element_descriptor,
                                                        amr))) {
                afu_release_irqs(ctx, ctx);
                cxl_adapter_context_put(ctx->afu->adapter);
                put_pid(ctx->pid);
                ctx->pid = NULL;
                cxl_ctx_put();
                cxl_context_mm_count_put(ctx);
                if (ctx->mm)
                        mm_context_remove_copro(ctx->mm);
                goto out;
        }

        rc = 0;
        if (work.flags & CXL_START_WORK_TID) {
                work.tid = ctx->tidr;
                if (copy_to_user(uwork, &work, sizeof(work)))
                        rc = -EFAULT;
        }

        ctx->status = STARTED;

out:
        mutex_unlock(&ctx->status_mutex);
        return rc;
}

static long afu_ioctl_process_element(struct cxl_context *ctx,
                                      int __user *upe)
{
        pr_devel("%s: pe: %i\n", __func__, ctx->pe);

        if (copy_to_user(upe, &ctx->external_pe, sizeof(__u32)))
                return -EFAULT;

        return 0;
}

static long afu_ioctl_get_afu_id(struct cxl_context *ctx,
                                 struct cxl_afu_id __user *upafuid)
{
        struct cxl_afu_id afuid = { 0 };

        afuid.card_id = ctx->afu->adapter->adapter_num;
        afuid.afu_offset = ctx->afu->slice;
        afuid.afu_mode = ctx->afu->current_mode;

        /* set the flag bit in case the afu is a slave */
        if (ctx->afu->current_mode == CXL_MODE_DIRECTED && !ctx->master)
                afuid.flags |= CXL_AFUID_FLAG_SLAVE;

        if (copy_to_user(upafuid, &afuid, sizeof(afuid)))
                return -EFAULT;

        return 0;
}

long afu_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct cxl_context *ctx = file->private_data;

        if (ctx->status == CLOSED)
                return -EIO;

        if (!cxl_ops->link_ok(ctx->afu->adapter, ctx->afu))
                return -EIO;

        pr_devel("afu_ioctl\n");
        switch (cmd) {
        case CXL_IOCTL_START_WORK:
                return afu_ioctl_start_work(ctx, (struct cxl_ioctl_start_work __user *)arg);
        case CXL_IOCTL_GET_PROCESS_ELEMENT:
                return afu_ioctl_process_element(ctx, (__u32 __user *)arg);
        case CXL_IOCTL_GET_AFU_ID:
                return afu_ioctl_get_afu_id(ctx, (struct cxl_afu_id __user *)
                                            arg);
        }
        return -EINVAL;
}

static long afu_compat_ioctl(struct file *file, unsigned int cmd,
                             unsigned long arg)
{
        return afu_ioctl(file, cmd, arg);
}

int afu_mmap(struct file *file, struct vm_area_struct *vm)
{
        struct cxl_context *ctx = file->private_data;

        /* AFU must be started before we can MMIO */
        if (ctx->status != STARTED)
                return -EIO;

        if (!cxl_ops->link_ok(ctx->afu->adapter, ctx->afu))
                return -EIO;

        return cxl_context_iomap(ctx, vm);
}

static inline bool ctx_event_pending(struct cxl_context *ctx)
{
        if (ctx->pending_irq || ctx->pending_fault || ctx->pending_afu_err)
                return true;

        if (ctx->afu_driver_ops && atomic_read(&ctx->afu_driver_events))
                return true;

        return false;
}

__poll_t afu_poll(struct file *file, struct poll_table_struct *poll)
{
        struct cxl_context *ctx = file->private_data;
        __poll_t mask = 0;
        unsigned long flags;


        poll_wait(file, &ctx->wq, poll);

        pr_devel("afu_poll wait done pe: %i\n", ctx->pe);

        spin_lock_irqsave(&ctx->lock, flags);
        if (ctx_event_pending(ctx))
                mask |= EPOLLIN | EPOLLRDNORM;
        else if (ctx->status == CLOSED)
                /* Only error on closed when there are no futher events pending
                 */
                mask |= EPOLLERR;
        spin_unlock_irqrestore(&ctx->lock, flags);

        pr_devel("afu_poll pe: %i returning %#x\n", ctx->pe, mask);

        return mask;
}

static ssize_t afu_driver_event_copy(struct cxl_context *ctx,
                                     char __user *buf,
                                     struct cxl_event *event,
                                     struct cxl_event_afu_driver_reserved *pl)
{
        /* Check event */
        if (!pl) {
                ctx->afu_driver_ops->event_delivered(ctx, pl, -EINVAL);
                return -EFAULT;
        }

        /* Check event size */
        event->header.size += pl->data_size;
        if (event->header.size > CXL_READ_MIN_SIZE) {
                ctx->afu_driver_ops->event_delivered(ctx, pl, -EINVAL);
                return -EFAULT;
        }

        /* Copy event header */
        if (copy_to_user(buf, event, sizeof(struct cxl_event_header))) {
                ctx->afu_driver_ops->event_delivered(ctx, pl, -EFAULT);
                return -EFAULT;
        }

        /* Copy event data */
        buf += sizeof(struct cxl_event_header);
        if (copy_to_user(buf, &pl->data, pl->data_size)) {
                ctx->afu_driver_ops->event_delivered(ctx, pl, -EFAULT);
                return -EFAULT;
        }

        ctx->afu_driver_ops->event_delivered(ctx, pl, 0); /* Success */
        return event->header.size;
}

ssize_t afu_read(struct file *file, char __user *buf, size_t count,
                        loff_t *off)
{
        struct cxl_context *ctx = file->private_data;
        struct cxl_event_afu_driver_reserved *pl = NULL;
        struct cxl_event event;
        unsigned long flags;
        int rc;
        DEFINE_WAIT(wait);

        if (!cxl_ops->link_ok(ctx->afu->adapter, ctx->afu))
                return -EIO;

        if (count < CXL_READ_MIN_SIZE)
                return -EINVAL;

        spin_lock_irqsave(&ctx->lock, flags);

        for (;;) {
                prepare_to_wait(&ctx->wq, &wait, TASK_INTERRUPTIBLE);
                if (ctx_event_pending(ctx) || (ctx->status == CLOSED))
                        break;

                if (!cxl_ops->link_ok(ctx->afu->adapter, ctx->afu)) {
                        rc = -EIO;
                        goto out;
                }

                if (file->f_flags & O_NONBLOCK) {
                        rc = -EAGAIN;
                        goto out;
                }

                if (signal_pending(current)) {
                        rc = -ERESTARTSYS;
                        goto out;
                }

                spin_unlock_irqrestore(&ctx->lock, flags);
                pr_devel("afu_read going to sleep...\n");
                schedule();
                pr_devel("afu_read woken up\n");
                spin_lock_irqsave(&ctx->lock, flags);
        }

        finish_wait(&ctx->wq, &wait);

        memset(&event, 0, sizeof(event));
        event.header.process_element = ctx->pe;
        event.header.size = sizeof(struct cxl_event_header);
        if (ctx->afu_driver_ops && atomic_read(&ctx->afu_driver_events)) {
                pr_devel("afu_read delivering AFU driver specific event\n");
                pl = ctx->afu_driver_ops->fetch_event(ctx);
                atomic_dec(&ctx->afu_driver_events);
                event.header.type = CXL_EVENT_AFU_DRIVER;
        } else if (ctx->pending_irq) {
                pr_devel("afu_read delivering AFU interrupt\n");
                event.header.size += sizeof(struct cxl_event_afu_interrupt);
                event.header.type = CXL_EVENT_AFU_INTERRUPT;
                event.irq.irq = find_first_bit(ctx->irq_bitmap, ctx->irq_count) + 1;
                clear_bit(event.irq.irq - 1, ctx->irq_bitmap);
                if (bitmap_empty(ctx->irq_bitmap, ctx->irq_count))
                        ctx->pending_irq = false;
        } else if (ctx->pending_fault) {
                pr_devel("afu_read delivering data storage fault\n");
                event.header.size += sizeof(struct cxl_event_data_storage);
                event.header.type = CXL_EVENT_DATA_STORAGE;
                event.fault.addr = ctx->fault_addr;
                event.fault.dsisr = ctx->fault_dsisr;
                ctx->pending_fault = false;
        } else if (ctx->pending_afu_err) {
                pr_devel("afu_read delivering afu error\n");
                event.header.size += sizeof(struct cxl_event_afu_error);
                event.header.type = CXL_EVENT_AFU_ERROR;
                event.afu_error.error = ctx->afu_err;
                ctx->pending_afu_err = false;
        } else if (ctx->status == CLOSED) {
                pr_devel("afu_read fatal error\n");
                spin_unlock_irqrestore(&ctx->lock, flags);
                return -EIO;
        } else
                WARN(1, "afu_read must be buggy\n");

        spin_unlock_irqrestore(&ctx->lock, flags);

        if (event.header.type == CXL_EVENT_AFU_DRIVER)
                return afu_driver_event_copy(ctx, buf, &event, pl);

        if (copy_to_user(buf, &event, event.header.size))
                return -EFAULT;
        return event.header.size;

out:
        finish_wait(&ctx->wq, &wait);
        spin_unlock_irqrestore(&ctx->lock, flags);
        return rc;
}

/* 
 * Note: if this is updated, we need to update api.c to patch the new ones in
 * too
 */
const struct file_operations afu_fops = {
        .owner          = THIS_MODULE,
        .open           = afu_open,
        .poll           = afu_poll,
        .read           = afu_read,
        .release        = afu_release,
        .unlocked_ioctl = afu_ioctl,
        .compat_ioctl   = afu_compat_ioctl,
        .mmap           = afu_mmap,
};

static const struct file_operations afu_master_fops = {
        .owner          = THIS_MODULE,
        .open           = afu_master_open,
        .poll           = afu_poll,
        .read           = afu_read,
        .release        = afu_release,
        .unlocked_ioctl = afu_ioctl,
        .compat_ioctl   = afu_compat_ioctl,
        .mmap           = afu_mmap,
};


static char *cxl_devnode(struct device *dev, umode_t *mode)
{
        if (cpu_has_feature(CPU_FTR_HVMODE) &&
            CXL_DEVT_IS_CARD(dev->devt)) {
                /*
                 * These minor numbers will eventually be used to program the
                 * PSL and AFUs once we have dynamic reprogramming support
                 */
                return NULL;
        }
        return kasprintf(GFP_KERNEL, "cxl/%s", dev_name(dev));
}

extern struct class *cxl_class;

static int cxl_add_chardev(struct cxl_afu *afu, dev_t devt, struct cdev *cdev,
                           struct device **chardev, char *postfix, char *desc,
                           const struct file_operations *fops)
{
        struct device *dev;
        int rc;

        cdev_init(cdev, fops);
        if ((rc = cdev_add(cdev, devt, 1))) {
                dev_err(&afu->dev, "Unable to add %s chardev: %i\n", desc, rc);
                return rc;
        }

        dev = device_create(cxl_class, &afu->dev, devt, afu,
                        "afu%i.%i%s", afu->adapter->adapter_num, afu->slice, postfix);
        if (IS_ERR(dev)) {
                dev_err(&afu->dev, "Unable to create %s chardev in sysfs: %i\n", desc, rc);
                rc = PTR_ERR(dev);
                goto err;
        }

        *chardev = dev;

        return 0;
err:
        cdev_del(cdev);
        return rc;
}

int cxl_chardev_d_afu_add(struct cxl_afu *afu)
{
        return cxl_add_chardev(afu, CXL_AFU_MKDEV_D(afu), &afu->afu_cdev_d,
                               &afu->chardev_d, "d", "dedicated",
                               &afu_master_fops); /* Uses master fops */
}

int cxl_chardev_m_afu_add(struct cxl_afu *afu)
{
        return cxl_add_chardev(afu, CXL_AFU_MKDEV_M(afu), &afu->afu_cdev_m,
                               &afu->chardev_m, "m", "master",
                               &afu_master_fops);
}

int cxl_chardev_s_afu_add(struct cxl_afu *afu)
{
        return cxl_add_chardev(afu, CXL_AFU_MKDEV_S(afu), &afu->afu_cdev_s,
                               &afu->chardev_s, "s", "shared",
                               &afu_fops);
}

void cxl_chardev_afu_remove(struct cxl_afu *afu)
{
        if (afu->chardev_d) {
                cdev_del(&afu->afu_cdev_d);
                device_unregister(afu->chardev_d);
                afu->chardev_d = NULL;
        }
        if (afu->chardev_m) {
                cdev_del(&afu->afu_cdev_m);
                device_unregister(afu->chardev_m);
                afu->chardev_m = NULL;
        }
        if (afu->chardev_s) {
                cdev_del(&afu->afu_cdev_s);
                device_unregister(afu->chardev_s);
                afu->chardev_s = NULL;
        }
}

int cxl_register_afu(struct cxl_afu *afu)
{
        afu->dev.class = cxl_class;

        return device_register(&afu->dev);
}

int cxl_register_adapter(struct cxl *adapter)
{
        adapter->dev.class = cxl_class;

        /*
         * Future: When we support dynamically reprogramming the PSL & AFU we
         * will expose the interface to do that via a chardev:
         * adapter->dev.devt = CXL_CARD_MKDEV(adapter);
         */

        return device_register(&adapter->dev);
}

dev_t cxl_get_dev(void)
{
        return cxl_dev;
}

int __init cxl_file_init(void)
{
        int rc;

        /*
         * If these change we really need to update API.  Either change some
         * flags or update API version number CXL_API_VERSION.
         */
        BUILD_BUG_ON(CXL_API_VERSION != 3);
        BUILD_BUG_ON(sizeof(struct cxl_ioctl_start_work) != 64);
        BUILD_BUG_ON(sizeof(struct cxl_event_header) != 8);
        BUILD_BUG_ON(sizeof(struct cxl_event_afu_interrupt) != 8);
        BUILD_BUG_ON(sizeof(struct cxl_event_data_storage) != 32);
        BUILD_BUG_ON(sizeof(struct cxl_event_afu_error) != 16);

        if ((rc = alloc_chrdev_region(&cxl_dev, 0, CXL_NUM_MINORS, "cxl"))) {
                pr_err("Unable to allocate CXL major number: %i\n", rc);
                return rc;
        }

        pr_devel("CXL device allocated, MAJOR %i\n", MAJOR(cxl_dev));

        cxl_class = class_create(THIS_MODULE, "cxl");
        if (IS_ERR(cxl_class)) {
                pr_err("Unable to create CXL class\n");
                rc = PTR_ERR(cxl_class);
                goto err;
        }
        cxl_class->devnode = cxl_devnode;

        return 0;

err:
        unregister_chrdev_region(cxl_dev, CXL_NUM_MINORS);
        return rc;
}

void cxl_file_exit(void)
{
        unregister_chrdev_region(cxl_dev, CXL_NUM_MINORS);
        class_destroy(cxl_class);
}