/*
 * 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/module.h>
#include <linux/kernel.h>
#include <linux/bitmap.h>
#include <linux/sched.h>
#include <linux/pid.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/debugfs.h>
#include <linux/slab.h>
#include <linux/idr.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"

/*
 * Allocates space for a CXL context.
 */
struct cxl_context *cxl_context_alloc(void)
{
        return kzalloc(sizeof(struct cxl_context), GFP_KERNEL);
}

/*
 * Initialises a CXL context.
 */
int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master)
{
        int i;

        ctx->afu = afu;
        ctx->master = master;
        ctx->pid = NULL; /* Set in start work ioctl */
        mutex_init(&ctx->mapping_lock);
        ctx->mapping = NULL;
        ctx->tidr = 0;
        ctx->assign_tidr = false;

        if (cxl_is_power8()) {
                spin_lock_init(&ctx->sste_lock);

                /*
                 * Allocate the segment table before we put it in the IDR so that we
                 * can always access it when dereferenced from IDR. For the same
                 * reason, the segment table is only destroyed after the context is
                 * removed from the IDR.  Access to this in the IOCTL is protected by
                 * Linux filesytem symantics (can't IOCTL until open is complete).
                 */
                i = cxl_alloc_sst(ctx);
                if (i)
                        return i;
        }

        INIT_WORK(&ctx->fault_work, cxl_handle_fault);

        init_waitqueue_head(&ctx->wq);
        spin_lock_init(&ctx->lock);

        ctx->irq_bitmap = NULL;
        ctx->pending_irq = false;
        ctx->pending_fault = false;
        ctx->pending_afu_err = false;

        INIT_LIST_HEAD(&ctx->irq_names);
        INIT_LIST_HEAD(&ctx->extra_irq_contexts);

        /*
         * When we have to destroy all contexts in cxl_context_detach_all() we
         * end up with afu_release_irqs() called from inside a
         * idr_for_each_entry(). Hence we need to make sure that anything
         * dereferenced from this IDR is ok before we allocate the IDR here.
         * This clears out the IRQ ranges to ensure this.
         */
        for (i = 0; i < CXL_IRQ_RANGES; i++)
                ctx->irqs.range[i] = 0;

        mutex_init(&ctx->status_mutex);

        ctx->status = OPENED;

        /*
         * Allocating IDR! We better make sure everything's setup that
         * dereferences from it.
         */
        mutex_lock(&afu->contexts_lock);
        idr_preload(GFP_KERNEL);
        i = idr_alloc(&ctx->afu->contexts_idr, ctx, ctx->afu->adapter->min_pe,
                      ctx->afu->num_procs, GFP_NOWAIT);
        idr_preload_end();
        mutex_unlock(&afu->contexts_lock);
        if (i < 0)
                return i;

        ctx->pe = i;
        if (cpu_has_feature(CPU_FTR_HVMODE)) {
                ctx->elem = &ctx->afu->native->spa[i];
                ctx->external_pe = ctx->pe;
        } else {
                ctx->external_pe = -1; /* assigned when attaching */
        }
        ctx->pe_inserted = false;

        /*
         * take a ref on the afu so that it stays alive at-least till
         * this context is reclaimed inside reclaim_ctx.
         */
        cxl_afu_get(afu);
        return 0;
}

void cxl_context_set_mapping(struct cxl_context *ctx,
                        struct address_space *mapping)
{
        mutex_lock(&ctx->mapping_lock);
        ctx->mapping = mapping;
        mutex_unlock(&ctx->mapping_lock);
}

static int cxl_mmap_fault(struct vm_fault *vmf)
{
        struct vm_area_struct *vma = vmf->vma;
        struct cxl_context *ctx = vma->vm_file->private_data;
        u64 area, offset;

        offset = vmf->pgoff << PAGE_SHIFT;

        pr_devel("%s: pe: %i address: 0x%lx offset: 0x%llx\n",
                        __func__, ctx->pe, vmf->address, offset);

        if (ctx->afu->current_mode == CXL_MODE_DEDICATED) {
                area = ctx->afu->psn_phys;
                if (offset >= ctx->afu->adapter->ps_size)
                        return VM_FAULT_SIGBUS;
        } else {
                area = ctx->psn_phys;
                if (offset >= ctx->psn_size)
                        return VM_FAULT_SIGBUS;
        }

        mutex_lock(&ctx->status_mutex);

        if (ctx->status != STARTED) {
                mutex_unlock(&ctx->status_mutex);
                pr_devel("%s: Context not started, failing problem state access\n", __func__);
                if (ctx->mmio_err_ff) {
                        if (!ctx->ff_page) {
                                ctx->ff_page = alloc_page(GFP_USER);
                                if (!ctx->ff_page)
                                        return VM_FAULT_OOM;
                                memset(page_address(ctx->ff_page), 0xff, PAGE_SIZE);
                        }
                        get_page(ctx->ff_page);
                        vmf->page = ctx->ff_page;
                        vma->vm_page_prot = pgprot_cached(vma->vm_page_prot);
                        return 0;
                }
                return VM_FAULT_SIGBUS;
        }

        vm_insert_pfn(vma, vmf->address, (area + offset) >> PAGE_SHIFT);

        mutex_unlock(&ctx->status_mutex);

        return VM_FAULT_NOPAGE;
}

static const struct vm_operations_struct cxl_mmap_vmops = {
        .fault = cxl_mmap_fault,
};

/*
 * Map a per-context mmio space into the given vma.
 */
int cxl_context_iomap(struct cxl_context *ctx, struct vm_area_struct *vma)
{
        u64 start = vma->vm_pgoff << PAGE_SHIFT;
        u64 len = vma->vm_end - vma->vm_start;

        if (ctx->afu->current_mode == CXL_MODE_DEDICATED) {
                if (start + len > ctx->afu->adapter->ps_size)
                        return -EINVAL;

                if (cxl_is_power9()) {
                        /*
                         * Make sure there is a valid problem state
                         * area space for this AFU.
                         */
                        if (ctx->master && !ctx->afu->psa) {
                                pr_devel("AFU doesn't support mmio space\n");
                                return -EINVAL;
                        }

                        /* Can't mmap until the AFU is enabled */
                        if (!ctx->afu->enabled)
                                return -EBUSY;
                }
        } else {
                if (start + len > ctx->psn_size)
                        return -EINVAL;

                /* Make sure there is a valid per process space for this AFU */
                if ((ctx->master && !ctx->afu->psa) || (!ctx->afu->pp_psa)) {
                        pr_devel("AFU doesn't support mmio space\n");
                        return -EINVAL;
                }

                /* Can't mmap until the AFU is enabled */
                if (!ctx->afu->enabled)
                        return -EBUSY;
        }

        pr_devel("%s: mmio physical: %llx pe: %i master:%i\n", __func__,
                 ctx->psn_phys, ctx->pe , ctx->master);

        vma->vm_flags |= VM_IO | VM_PFNMAP;
        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
        vma->vm_ops = &cxl_mmap_vmops;
        return 0;
}

/*
 * Detach a context from the hardware. This disables interrupts and doesn't
 * return until all outstanding interrupts for this context have completed. The
 * hardware should no longer access *ctx after this has returned.
 */
int __detach_context(struct cxl_context *ctx)
{
        enum cxl_context_status status;

        mutex_lock(&ctx->status_mutex);
        status = ctx->status;
        ctx->status = CLOSED;
        mutex_unlock(&ctx->status_mutex);
        if (status != STARTED)
                return -EBUSY;

        /* Only warn if we detached while the link was OK.
         * If detach fails when hw is down, we don't care.
         */
        WARN_ON(cxl_ops->detach_process(ctx) &&
                cxl_ops->link_ok(ctx->afu->adapter, ctx->afu));
        flush_work(&ctx->fault_work); /* Only needed for dedicated process */

        /*
         * Wait until no further interrupts are presented by the PSL
         * for this context.
         */
        if (cxl_ops->irq_wait)
                cxl_ops->irq_wait(ctx);

        /* release the reference to the group leader and mm handling pid */
        put_pid(ctx->pid);

        cxl_ctx_put();

        /* Decrease the attached context count on the adapter */
        cxl_adapter_context_put(ctx->afu->adapter);

        /* Decrease the mm count on the context */
        cxl_context_mm_count_put(ctx);
        if (ctx->mm)
                mm_context_remove_copro(ctx->mm);
        ctx->mm = NULL;

        return 0;
}

/*
 * Detach the given context from the AFU. This doesn't actually
 * free the context but it should stop the context running in hardware
 * (ie. prevent this context from generating any further interrupts
 * so that it can be freed).
 */
void cxl_context_detach(struct cxl_context *ctx)
{
        int rc;

        rc = __detach_context(ctx);
        if (rc)
                return;

        afu_release_irqs(ctx, ctx);
        wake_up_all(&ctx->wq);
}

/*
 * Detach all contexts on the given AFU.
 */
void cxl_context_detach_all(struct cxl_afu *afu)
{
        struct cxl_context *ctx;
        int tmp;

        mutex_lock(&afu->contexts_lock);
        idr_for_each_entry(&afu->contexts_idr, ctx, tmp) {
                /*
                 * Anything done in here needs to be setup before the IDR is
                 * created and torn down after the IDR removed
                 */
                cxl_context_detach(ctx);

                /*
                 * We are force detaching - remove any active PSA mappings so
                 * userspace cannot interfere with the card if it comes back.
                 * Easiest way to exercise this is to unbind and rebind the
                 * driver via sysfs while it is in use.
                 */
                mutex_lock(&ctx->mapping_lock);
                if (ctx->mapping)
                        unmap_mapping_range(ctx->mapping, 0, 0, 1);
                mutex_unlock(&ctx->mapping_lock);
        }
        mutex_unlock(&afu->contexts_lock);
}

static void reclaim_ctx(struct rcu_head *rcu)
{
        struct cxl_context *ctx = container_of(rcu, struct cxl_context, rcu);

        if (cxl_is_power8())
                free_page((u64)ctx->sstp);
        if (ctx->ff_page)
                __free_page(ctx->ff_page);
        ctx->sstp = NULL;

        kfree(ctx->irq_bitmap);

        /* Drop ref to the afu device taken during cxl_context_init */
        cxl_afu_put(ctx->afu);

        kfree(ctx);
}

void cxl_context_free(struct cxl_context *ctx)
{
        if (ctx->kernelapi && ctx->mapping)
                cxl_release_mapping(ctx);
        mutex_lock(&ctx->afu->contexts_lock);
        idr_remove(&ctx->afu->contexts_idr, ctx->pe);
        mutex_unlock(&ctx->afu->contexts_lock);
        call_rcu(&ctx->rcu, reclaim_ctx);
}

void cxl_context_mm_count_get(struct cxl_context *ctx)
{
        if (ctx->mm)
                atomic_inc(&ctx->mm->mm_count);
}

void cxl_context_mm_count_put(struct cxl_context *ctx)
{
        if (ctx->mm)
                mmdrop(ctx->mm);
}