/*
 * videobuf2-dma-sg.c - dma scatter/gather memory allocator for videobuf2
 *
 * Copyright (C) 2010 Samsung Electronics
 *
 * Author: Andrzej Pietrasiewicz <andrzejtp2010@gmail.com>
 *
 * 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.
 */

#include <linux/module.h>
#include <linux/mm.h>
#include <linux/refcount.h>
#include <linux/scatterlist.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>

#include <media/videobuf2-v4l2.h>
#include <media/videobuf2-memops.h>
#include <media/videobuf2-dma-sg.h>

static int debug;
module_param(debug, int, 0644);

#define dprintk(level, fmt, arg...)                                     \
        do {                                                            \
                if (debug >= level)                                     \
                        printk(KERN_DEBUG "vb2-dma-sg: " fmt, ## arg);  \
        } while (0)

struct vb2_dma_sg_buf {
        struct device                   *dev;
        void                            *vaddr;
        struct page                     **pages;
        struct frame_vector             *vec;
        int                             offset;
        enum dma_data_direction         dma_dir;
        struct sg_table                 sg_table;
        /*
         * This will point to sg_table when used with the MMAP or USERPTR
         * memory model, and to the dma_buf sglist when used with the
         * DMABUF memory model.
         */
        struct sg_table                 *dma_sgt;
        size_t                          size;
        unsigned int                    num_pages;
        refcount_t                      refcount;
        struct vb2_vmarea_handler       handler;

        struct dma_buf_attachment       *db_attach;
};

static void vb2_dma_sg_put(void *buf_priv);

static int vb2_dma_sg_alloc_compacted(struct vb2_dma_sg_buf *buf,
                gfp_t gfp_flags)
{
        unsigned int last_page = 0;
        unsigned long size = buf->size;

        while (size > 0) {
                struct page *pages;
                int order;
                int i;

                order = get_order(size);
                /* Don't over allocate*/
                if ((PAGE_SIZE << order) > size)
                        order--;

                pages = NULL;
                while (!pages) {
                        pages = alloc_pages(GFP_KERNEL | __GFP_ZERO |
                                        __GFP_NOWARN | gfp_flags, order);
                        if (pages)
                                break;

                        if (order == 0) {
                                while (last_page--)
                                        __free_page(buf->pages[last_page]);
                                return -ENOMEM;
                        }
                        order--;
                }

                split_page(pages, order);
                for (i = 0; i < (1 << order); i++)
                        buf->pages[last_page++] = &pages[i];

                size -= PAGE_SIZE << order;
        }

        return 0;
}

static void *vb2_dma_sg_alloc(struct device *dev, unsigned long dma_attrs,
                              unsigned long size, enum dma_data_direction dma_dir,
                              gfp_t gfp_flags)
{
        struct vb2_dma_sg_buf *buf;
        struct sg_table *sgt;
        int ret;
        int num_pages;

        if (WARN_ON(!dev))
                return ERR_PTR(-EINVAL);

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

        buf->vaddr = NULL;
        buf->dma_dir = dma_dir;
        buf->offset = 0;
        buf->size = size;
        /* size is already page aligned */
        buf->num_pages = size >> PAGE_SHIFT;
        buf->dma_sgt = &buf->sg_table;

        buf->pages = kvmalloc_array(buf->num_pages, sizeof(struct page *),
                                    GFP_KERNEL | __GFP_ZERO);
        if (!buf->pages)
                goto fail_pages_array_alloc;

        ret = vb2_dma_sg_alloc_compacted(buf, gfp_flags);
        if (ret)
                goto fail_pages_alloc;

        ret = sg_alloc_table_from_pages(buf->dma_sgt, buf->pages,
                        buf->num_pages, 0, size, GFP_KERNEL);
        if (ret)
                goto fail_table_alloc;

        /* Prevent the device from being released while the buffer is used */
        buf->dev = get_device(dev);

        sgt = &buf->sg_table;
        /*
         * No need to sync to the device, this will happen later when the
         * prepare() memop is called.
         */
        sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
                                      buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
        if (!sgt->nents)
                goto fail_map;

        buf->handler.refcount = &buf->refcount;
        buf->handler.put = vb2_dma_sg_put;
        buf->handler.arg = buf;

        refcount_set(&buf->refcount, 1);

        dprintk(1, "%s: Allocated buffer of %d pages\n",
                __func__, buf->num_pages);
        return buf;

fail_map:
        put_device(buf->dev);
        sg_free_table(buf->dma_sgt);
fail_table_alloc:
        num_pages = buf->num_pages;
        while (num_pages--)
                __free_page(buf->pages[num_pages]);
fail_pages_alloc:
        kvfree(buf->pages);
fail_pages_array_alloc:
        kfree(buf);
        return ERR_PTR(-ENOMEM);
}

static void vb2_dma_sg_put(void *buf_priv)
{
        struct vb2_dma_sg_buf *buf = buf_priv;
        struct sg_table *sgt = &buf->sg_table;
        int i = buf->num_pages;

        if (refcount_dec_and_test(&buf->refcount)) {
                dprintk(1, "%s: Freeing buffer of %d pages\n", __func__,
                        buf->num_pages);
                dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
                                   buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
                if (buf->vaddr)
                        vm_unmap_ram(buf->vaddr, buf->num_pages);
                sg_free_table(buf->dma_sgt);
                while (--i >= 0)
                        __free_page(buf->pages[i]);
                kvfree(buf->pages);
                put_device(buf->dev);
                kfree(buf);
        }
}

static void vb2_dma_sg_prepare(void *buf_priv)
{
        struct vb2_dma_sg_buf *buf = buf_priv;
        struct sg_table *sgt = buf->dma_sgt;

        /* DMABUF exporter will flush the cache for us */
        if (buf->db_attach)
                return;

        dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->orig_nents,
                               buf->dma_dir);
}

static void vb2_dma_sg_finish(void *buf_priv)
{
        struct vb2_dma_sg_buf *buf = buf_priv;
        struct sg_table *sgt = buf->dma_sgt;

        /* DMABUF exporter will flush the cache for us */
        if (buf->db_attach)
                return;

        dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
}

static void *vb2_dma_sg_get_userptr(struct device *dev, unsigned long vaddr,
                                    unsigned long size,
                                    enum dma_data_direction dma_dir)
{
        struct vb2_dma_sg_buf *buf;
        struct sg_table *sgt;
        struct frame_vector *vec;

        if (WARN_ON(!dev))
                return ERR_PTR(-EINVAL);

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

        buf->vaddr = NULL;
        buf->dev = dev;
        buf->dma_dir = dma_dir;
        buf->offset = vaddr & ~PAGE_MASK;
        buf->size = size;
        buf->dma_sgt = &buf->sg_table;
        vec = vb2_create_framevec(vaddr, size);
        if (IS_ERR(vec))
                goto userptr_fail_pfnvec;
        buf->vec = vec;

        buf->pages = frame_vector_pages(vec);
        if (IS_ERR(buf->pages))
                goto userptr_fail_sgtable;
        buf->num_pages = frame_vector_count(vec);

        if (sg_alloc_table_from_pages(buf->dma_sgt, buf->pages,
                        buf->num_pages, buf->offset, size, 0))
                goto userptr_fail_sgtable;

        sgt = &buf->sg_table;
        /*
         * No need to sync to the device, this will happen later when the
         * prepare() memop is called.
         */
        sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
                                      buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
        if (!sgt->nents)
                goto userptr_fail_map;

        return buf;

userptr_fail_map:
        sg_free_table(&buf->sg_table);
userptr_fail_sgtable:
        vb2_destroy_framevec(vec);
userptr_fail_pfnvec:
        kfree(buf);
        return ERR_PTR(-ENOMEM);
}

/*
 * @put_userptr: inform the allocator that a USERPTR buffer will no longer
 *               be used
 */
static void vb2_dma_sg_put_userptr(void *buf_priv)
{
        struct vb2_dma_sg_buf *buf = buf_priv;
        struct sg_table *sgt = &buf->sg_table;
        int i = buf->num_pages;

        dprintk(1, "%s: Releasing userspace buffer of %d pages\n",
               __func__, buf->num_pages);
        dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir,
                           DMA_ATTR_SKIP_CPU_SYNC);
        if (buf->vaddr)
                vm_unmap_ram(buf->vaddr, buf->num_pages);
        sg_free_table(buf->dma_sgt);
        if (buf->dma_dir == DMA_FROM_DEVICE ||
            buf->dma_dir == DMA_BIDIRECTIONAL)
                while (--i >= 0)
                        set_page_dirty_lock(buf->pages[i]);
        vb2_destroy_framevec(buf->vec);
        kfree(buf);
}

static void *vb2_dma_sg_vaddr(void *buf_priv)
{
        struct vb2_dma_sg_buf *buf = buf_priv;

        BUG_ON(!buf);

        if (!buf->vaddr) {
                if (buf->db_attach)
                        buf->vaddr = dma_buf_vmap(buf->db_attach->dmabuf);
                else
                        buf->vaddr = vm_map_ram(buf->pages,
                                        buf->num_pages, -1, PAGE_KERNEL);
        }

        /* add offset in case userptr is not page-aligned */
        return buf->vaddr ? buf->vaddr + buf->offset : NULL;
}

static unsigned int vb2_dma_sg_num_users(void *buf_priv)
{
        struct vb2_dma_sg_buf *buf = buf_priv;

        return refcount_read(&buf->refcount);
}

static int vb2_dma_sg_mmap(void *buf_priv, struct vm_area_struct *vma)
{
        struct vb2_dma_sg_buf *buf = buf_priv;
        int err;

        if (!buf) {
                printk(KERN_ERR "No memory to map\n");
                return -EINVAL;
        }

        err = vm_map_pages(vma, buf->pages, buf->num_pages);
        if (err) {
                printk(KERN_ERR "Remapping memory, error: %d\n", err);
                return err;
        }

        /*
         * Use common vm_area operations to track buffer refcount.
         */
        vma->vm_private_data    = &buf->handler;
        vma->vm_ops             = &vb2_common_vm_ops;

        vma->vm_ops->open(vma);

        return 0;
}

/*********************************************/
/*         DMABUF ops for exporters          */
/*********************************************/

struct vb2_dma_sg_attachment {
        struct sg_table sgt;
        enum dma_data_direction dma_dir;
};

static int vb2_dma_sg_dmabuf_ops_attach(struct dma_buf *dbuf,
        struct dma_buf_attachment *dbuf_attach)
{
        struct vb2_dma_sg_attachment *attach;
        unsigned int i;
        struct scatterlist *rd, *wr;
        struct sg_table *sgt;
        struct vb2_dma_sg_buf *buf = dbuf->priv;
        int ret;

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

        sgt = &attach->sgt;
        /* Copy the buf->base_sgt scatter list to the attachment, as we can't
         * map the same scatter list to multiple attachments at the same time.
         */
        ret = sg_alloc_table(sgt, buf->dma_sgt->orig_nents, GFP_KERNEL);
        if (ret) {
                kfree(attach);
                return -ENOMEM;
        }

        rd = buf->dma_sgt->sgl;
        wr = sgt->sgl;
        for (i = 0; i < sgt->orig_nents; ++i) {
                sg_set_page(wr, sg_page(rd), rd->length, rd->offset);
                rd = sg_next(rd);
                wr = sg_next(wr);
        }

        attach->dma_dir = DMA_NONE;
        dbuf_attach->priv = attach;

        return 0;
}

static void vb2_dma_sg_dmabuf_ops_detach(struct dma_buf *dbuf,
        struct dma_buf_attachment *db_attach)
{
        struct vb2_dma_sg_attachment *attach = db_attach->priv;
        struct sg_table *sgt;

        if (!attach)
                return;

        sgt = &attach->sgt;

        /* release the scatterlist cache */
        if (attach->dma_dir != DMA_NONE)
                dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
                        attach->dma_dir);
        sg_free_table(sgt);
        kfree(attach);
        db_attach->priv = NULL;
}

static struct sg_table *vb2_dma_sg_dmabuf_ops_map(
        struct dma_buf_attachment *db_attach, enum dma_data_direction dma_dir)
{
        struct vb2_dma_sg_attachment *attach = db_attach->priv;
        /* stealing dmabuf mutex to serialize map/unmap operations */
        struct mutex *lock = &db_attach->dmabuf->lock;
        struct sg_table *sgt;

        mutex_lock(lock);

        sgt = &attach->sgt;
        /* return previously mapped sg table */
        if (attach->dma_dir == dma_dir) {
                mutex_unlock(lock);
                return sgt;
        }

        /* release any previous cache */
        if (attach->dma_dir != DMA_NONE) {
                dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
                        attach->dma_dir);
                attach->dma_dir = DMA_NONE;
        }

        /* mapping to the client with new direction */
        sgt->nents = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
                                dma_dir);
        if (!sgt->nents) {
                pr_err("failed to map scatterlist\n");
                mutex_unlock(lock);
                return ERR_PTR(-EIO);
        }

        attach->dma_dir = dma_dir;

        mutex_unlock(lock);

        return sgt;
}

static void vb2_dma_sg_dmabuf_ops_unmap(struct dma_buf_attachment *db_attach,
        struct sg_table *sgt, enum dma_data_direction dma_dir)
{
        /* nothing to be done here */
}

static void vb2_dma_sg_dmabuf_ops_release(struct dma_buf *dbuf)
{
        /* drop reference obtained in vb2_dma_sg_get_dmabuf */
        vb2_dma_sg_put(dbuf->priv);
}

static void *vb2_dma_sg_dmabuf_ops_kmap(struct dma_buf *dbuf, unsigned long pgnum)
{
        struct vb2_dma_sg_buf *buf = dbuf->priv;

        return buf->vaddr ? buf->vaddr + pgnum * PAGE_SIZE : NULL;
}

static void *vb2_dma_sg_dmabuf_ops_vmap(struct dma_buf *dbuf)
{
        struct vb2_dma_sg_buf *buf = dbuf->priv;

        return vb2_dma_sg_vaddr(buf);
}

static int vb2_dma_sg_dmabuf_ops_mmap(struct dma_buf *dbuf,
        struct vm_area_struct *vma)
{
        return vb2_dma_sg_mmap(dbuf->priv, vma);
}

static const struct dma_buf_ops vb2_dma_sg_dmabuf_ops = {
        .attach = vb2_dma_sg_dmabuf_ops_attach,
        .detach = vb2_dma_sg_dmabuf_ops_detach,
        .map_dma_buf = vb2_dma_sg_dmabuf_ops_map,
        .unmap_dma_buf = vb2_dma_sg_dmabuf_ops_unmap,
        .map = vb2_dma_sg_dmabuf_ops_kmap,
        .vmap = vb2_dma_sg_dmabuf_ops_vmap,
        .mmap = vb2_dma_sg_dmabuf_ops_mmap,
        .release = vb2_dma_sg_dmabuf_ops_release,
};

static struct dma_buf *vb2_dma_sg_get_dmabuf(void *buf_priv, unsigned long flags)
{
        struct vb2_dma_sg_buf *buf = buf_priv;
        struct dma_buf *dbuf;
        DEFINE_DMA_BUF_EXPORT_INFO(exp_info);

        exp_info.ops = &vb2_dma_sg_dmabuf_ops;
        exp_info.size = buf->size;
        exp_info.flags = flags;
        exp_info.priv = buf;

        if (WARN_ON(!buf->dma_sgt))
                return NULL;

        dbuf = dma_buf_export(&exp_info);
        if (IS_ERR(dbuf))
                return NULL;

        /* dmabuf keeps reference to vb2 buffer */
        refcount_inc(&buf->refcount);

        return dbuf;
}

/*********************************************/
/*       callbacks for DMABUF buffers        */
/*********************************************/

static int vb2_dma_sg_map_dmabuf(void *mem_priv)
{
        struct vb2_dma_sg_buf *buf = mem_priv;
        struct sg_table *sgt;

        if (WARN_ON(!buf->db_attach)) {
                pr_err("trying to pin a non attached buffer\n");
                return -EINVAL;
        }

        if (WARN_ON(buf->dma_sgt)) {
                pr_err("dmabuf buffer is already pinned\n");
                return 0;
        }

        /* get the associated scatterlist for this buffer */
        sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
        if (IS_ERR(sgt)) {
                pr_err("Error getting dmabuf scatterlist\n");
                return -EINVAL;
        }

        buf->dma_sgt = sgt;
        buf->vaddr = NULL;

        return 0;
}

static void vb2_dma_sg_unmap_dmabuf(void *mem_priv)
{
        struct vb2_dma_sg_buf *buf = mem_priv;
        struct sg_table *sgt = buf->dma_sgt;

        if (WARN_ON(!buf->db_attach)) {
                pr_err("trying to unpin a not attached buffer\n");
                return;
        }

        if (WARN_ON(!sgt)) {
                pr_err("dmabuf buffer is already unpinned\n");
                return;
        }

        if (buf->vaddr) {
                dma_buf_vunmap(buf->db_attach->dmabuf, buf->vaddr);
                buf->vaddr = NULL;
        }
        dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);

        buf->dma_sgt = NULL;
}

static void vb2_dma_sg_detach_dmabuf(void *mem_priv)
{
        struct vb2_dma_sg_buf *buf = mem_priv;

        /* if vb2 works correctly you should never detach mapped buffer */
        if (WARN_ON(buf->dma_sgt))
                vb2_dma_sg_unmap_dmabuf(buf);

        /* detach this attachment */
        dma_buf_detach(buf->db_attach->dmabuf, buf->db_attach);
        kfree(buf);
}

static void *vb2_dma_sg_attach_dmabuf(struct device *dev, struct dma_buf *dbuf,
        unsigned long size, enum dma_data_direction dma_dir)
{
        struct vb2_dma_sg_buf *buf;
        struct dma_buf_attachment *dba;

        if (WARN_ON(!dev))
                return ERR_PTR(-EINVAL);

        if (dbuf->size < size)
                return ERR_PTR(-EFAULT);

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

        buf->dev = dev;
        /* create attachment for the dmabuf with the user device */
        dba = dma_buf_attach(dbuf, buf->dev);
        if (IS_ERR(dba)) {
                pr_err("failed to attach dmabuf\n");
                kfree(buf);
                return dba;
        }

        buf->dma_dir = dma_dir;
        buf->size = size;
        buf->db_attach = dba;

        return buf;
}

static void *vb2_dma_sg_cookie(void *buf_priv)
{
        struct vb2_dma_sg_buf *buf = buf_priv;

        return buf->dma_sgt;
}

const struct vb2_mem_ops vb2_dma_sg_memops = {
        .alloc          = vb2_dma_sg_alloc,
        .put            = vb2_dma_sg_put,
        .get_userptr    = vb2_dma_sg_get_userptr,
        .put_userptr    = vb2_dma_sg_put_userptr,
        .prepare        = vb2_dma_sg_prepare,
        .finish         = vb2_dma_sg_finish,
        .vaddr          = vb2_dma_sg_vaddr,
        .mmap           = vb2_dma_sg_mmap,
        .num_users      = vb2_dma_sg_num_users,
        .get_dmabuf     = vb2_dma_sg_get_dmabuf,
        .map_dmabuf     = vb2_dma_sg_map_dmabuf,
        .unmap_dmabuf   = vb2_dma_sg_unmap_dmabuf,
        .attach_dmabuf  = vb2_dma_sg_attach_dmabuf,
        .detach_dmabuf  = vb2_dma_sg_detach_dmabuf,
        .cookie         = vb2_dma_sg_cookie,
};
EXPORT_SYMBOL_GPL(vb2_dma_sg_memops);

MODULE_DESCRIPTION("dma scatter/gather memory handling routines for videobuf2");
MODULE_AUTHOR("Andrzej Pietrasiewicz");
MODULE_LICENSE("GPL");