// SPDX-License-Identifier: GPL-2.0 OR MIT

/*
 *  Xen para-virtual DRM device
 *
 * Copyright (C) 2016-2018 EPAM Systems Inc.
 *
 * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
 */

#include <linux/dma-buf.h>
#include <linux/scatterlist.h>
#include <linux/shmem_fs.h>

#include <drm/drm_fb_helper.h>
#include <drm/drm_gem.h>
#include <drm/drm_prime.h>
#include <drm/drm_probe_helper.h>

#include <xen/balloon.h>
#include <xen/xen.h>

#include "xen_drm_front.h"
#include "xen_drm_front_gem.h"

struct xen_gem_object {
        struct drm_gem_object base;

        size_t num_pages;
        struct page **pages;

        /* set for buffers allocated by the backend */
        bool be_alloc;

        /* this is for imported PRIME buffer */
        struct sg_table *sgt_imported;
};

static inline struct xen_gem_object *
to_xen_gem_obj(struct drm_gem_object *gem_obj)
{
        return container_of(gem_obj, struct xen_gem_object, base);
}

static int gem_alloc_pages_array(struct xen_gem_object *xen_obj,
                                 size_t buf_size)
{
        xen_obj->num_pages = DIV_ROUND_UP(buf_size, PAGE_SIZE);
        xen_obj->pages = kvmalloc_array(xen_obj->num_pages,
                                        sizeof(struct page *), GFP_KERNEL);
        return !xen_obj->pages ? -ENOMEM : 0;
}

static void gem_free_pages_array(struct xen_gem_object *xen_obj)
{
        kvfree(xen_obj->pages);
        xen_obj->pages = NULL;
}

static const struct vm_operations_struct xen_drm_drv_vm_ops = {
        .open           = drm_gem_vm_open,
        .close          = drm_gem_vm_close,
};

static const struct drm_gem_object_funcs xen_drm_front_gem_object_funcs = {
        .free = xen_drm_front_gem_object_free,
        .get_sg_table = xen_drm_front_gem_get_sg_table,
        .vmap = xen_drm_front_gem_prime_vmap,
        .vunmap = xen_drm_front_gem_prime_vunmap,
        .vm_ops = &xen_drm_drv_vm_ops,
};

static struct xen_gem_object *gem_create_obj(struct drm_device *dev,
                                             size_t size)
{
        struct xen_gem_object *xen_obj;
        int ret;

        xen_obj = kzalloc(sizeof(*xen_obj), GFP_KERNEL);
        if (!xen_obj)
                return ERR_PTR(-ENOMEM);

        xen_obj->base.funcs = &xen_drm_front_gem_object_funcs;

        ret = drm_gem_object_init(dev, &xen_obj->base, size);
        if (ret < 0) {
                kfree(xen_obj);
                return ERR_PTR(ret);
        }

        return xen_obj;
}

static struct xen_gem_object *gem_create(struct drm_device *dev, size_t size)
{
        struct xen_drm_front_drm_info *drm_info = dev->dev_private;
        struct xen_gem_object *xen_obj;
        int ret;

        size = round_up(size, PAGE_SIZE);
        xen_obj = gem_create_obj(dev, size);
        if (IS_ERR(xen_obj))
                return xen_obj;

        if (drm_info->front_info->cfg.be_alloc) {
                /*
                 * backend will allocate space for this buffer, so
                 * only allocate array of pointers to pages
                 */
                ret = gem_alloc_pages_array(xen_obj, size);
                if (ret < 0)
                        goto fail;

                /*
                 * allocate ballooned pages which will be used to map
                 * grant references provided by the backend
                 */
                ret = xen_alloc_unpopulated_pages(xen_obj->num_pages,
                                                  xen_obj->pages);
                if (ret < 0) {
                        DRM_ERROR("Cannot allocate %zu ballooned pages: %d\n",
                                  xen_obj->num_pages, ret);
                        gem_free_pages_array(xen_obj);
                        goto fail;
                }

                xen_obj->be_alloc = true;
                return xen_obj;
        }
        /*
         * need to allocate backing pages now, so we can share those
         * with the backend
         */
        xen_obj->num_pages = DIV_ROUND_UP(size, PAGE_SIZE);
        xen_obj->pages = drm_gem_get_pages(&xen_obj->base);
        if (IS_ERR(xen_obj->pages)) {
                ret = PTR_ERR(xen_obj->pages);
                xen_obj->pages = NULL;
                goto fail;
        }

        return xen_obj;

fail:
        DRM_ERROR("Failed to allocate buffer with size %zu\n", size);
        return ERR_PTR(ret);
}

struct drm_gem_object *xen_drm_front_gem_create(struct drm_device *dev,
                                                size_t size)
{
        struct xen_gem_object *xen_obj;

        xen_obj = gem_create(dev, size);
        if (IS_ERR(xen_obj))
                return ERR_CAST(xen_obj);

        return &xen_obj->base;
}

void xen_drm_front_gem_free_object_unlocked(struct drm_gem_object *gem_obj)
{
        struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);

        if (xen_obj->base.import_attach) {
                drm_prime_gem_destroy(&xen_obj->base, xen_obj->sgt_imported);
                gem_free_pages_array(xen_obj);
        } else {
                if (xen_obj->pages) {
                        if (xen_obj->be_alloc) {
                                xen_free_unpopulated_pages(xen_obj->num_pages,
                                                           xen_obj->pages);
                                gem_free_pages_array(xen_obj);
                        } else {
                                drm_gem_put_pages(&xen_obj->base,
                                                  xen_obj->pages, true, false);
                        }
                }
        }
        drm_gem_object_release(gem_obj);
        kfree(xen_obj);
}

struct page **xen_drm_front_gem_get_pages(struct drm_gem_object *gem_obj)
{
        struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);

        return xen_obj->pages;
}

struct sg_table *xen_drm_front_gem_get_sg_table(struct drm_gem_object *gem_obj)
{
        struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);

        if (!xen_obj->pages)
                return ERR_PTR(-ENOMEM);

        return drm_prime_pages_to_sg(gem_obj->dev,
                                     xen_obj->pages, xen_obj->num_pages);
}

struct drm_gem_object *
xen_drm_front_gem_import_sg_table(struct drm_device *dev,
                                  struct dma_buf_attachment *attach,
                                  struct sg_table *sgt)
{
        struct xen_drm_front_drm_info *drm_info = dev->dev_private;
        struct xen_gem_object *xen_obj;
        size_t size;
        int ret;

        size = attach->dmabuf->size;
        xen_obj = gem_create_obj(dev, size);
        if (IS_ERR(xen_obj))
                return ERR_CAST(xen_obj);

        ret = gem_alloc_pages_array(xen_obj, size);
        if (ret < 0)
                return ERR_PTR(ret);

        xen_obj->sgt_imported = sgt;

        ret = drm_prime_sg_to_page_array(sgt, xen_obj->pages,
                                         xen_obj->num_pages);
        if (ret < 0)
                return ERR_PTR(ret);

        ret = xen_drm_front_dbuf_create(drm_info->front_info,
                                        xen_drm_front_dbuf_to_cookie(&xen_obj->base),
                                        0, 0, 0, size, sgt->sgl->offset,
                                        xen_obj->pages);
        if (ret < 0)
                return ERR_PTR(ret);

        DRM_DEBUG("Imported buffer of size %zu with nents %u\n",
                  size, sgt->orig_nents);

        return &xen_obj->base;
}

static int gem_mmap_obj(struct xen_gem_object *xen_obj,
                        struct vm_area_struct *vma)
{
        int ret;

        /*
         * clear the VM_PFNMAP flag that was set by drm_gem_mmap(), and set the
         * vm_pgoff (used as a fake buffer offset by DRM) to 0 as we want to map
         * the whole buffer.
         */
        vma->vm_flags &= ~VM_PFNMAP;
        vma->vm_flags |= VM_MIXEDMAP;
        vma->vm_pgoff = 0;
        /*
         * According to Xen on ARM ABI (xen/include/public/arch-arm.h):
         * all memory which is shared with other entities in the system
         * (including the hypervisor and other guests) must reside in memory
         * which is mapped as Normal Inner Write-Back Outer Write-Back
         * Inner-Shareable.
         */
        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);

        /*
         * vm_operations_struct.fault handler will be called if CPU access
         * to VM is here. For GPUs this isn't the case, because CPU
         * doesn't touch the memory. Insert pages now, so both CPU and GPU are
         * happy.
         * FIXME: as we insert all the pages now then no .fault handler must
         * be called, so don't provide one
         */
        ret = vm_map_pages(vma, xen_obj->pages, xen_obj->num_pages);
        if (ret < 0)
                DRM_ERROR("Failed to map pages into vma: %d\n", ret);

        return ret;
}

int xen_drm_front_gem_mmap(struct file *filp, struct vm_area_struct *vma)
{
        struct xen_gem_object *xen_obj;
        struct drm_gem_object *gem_obj;
        int ret;

        ret = drm_gem_mmap(filp, vma);
        if (ret < 0)
                return ret;

        gem_obj = vma->vm_private_data;
        xen_obj = to_xen_gem_obj(gem_obj);
        return gem_mmap_obj(xen_obj, vma);
}

int xen_drm_front_gem_prime_vmap(struct drm_gem_object *gem_obj, struct dma_buf_map *map)
{
        struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);
        void *vaddr;

        if (!xen_obj->pages)
                return -ENOMEM;

        /* Please see comment in gem_mmap_obj on mapping and attributes. */
        vaddr = vmap(xen_obj->pages, xen_obj->num_pages,
                     VM_MAP, PAGE_KERNEL);
        if (!vaddr)
                return -ENOMEM;
        dma_buf_map_set_vaddr(map, vaddr);

        return 0;
}

void xen_drm_front_gem_prime_vunmap(struct drm_gem_object *gem_obj,
                                    struct dma_buf_map *map)
{
        vunmap(map->vaddr);
}

int xen_drm_front_gem_prime_mmap(struct drm_gem_object *gem_obj,
                                 struct vm_area_struct *vma)
{
        struct xen_gem_object *xen_obj;
        int ret;

        ret = drm_gem_mmap_obj(gem_obj, gem_obj->size, vma);
        if (ret < 0)
                return ret;

        xen_obj = to_xen_gem_obj(gem_obj);
        return gem_mmap_obj(xen_obj, vma);
}