/*
 * videobuf2-dma-contig.c - DMA contig memory allocator for videobuf2
 *
 * Copyright (C) 2010 Samsung Electronics
 *
 * Author: Pawel Osciak <pawel@osciak.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/dma-buf.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/dma-mapping.h>

#include <media/videobuf2-core.h>
#include <media/videobuf2-dma-contig.h>
#include <media/videobuf2-memops.h>

struct vb2_dc_conf {
        struct device           *dev;
};

struct vb2_dc_buf {
        struct device                   *dev;
        void                            *vaddr;
        unsigned long                   size;
        dma_addr_t                      dma_addr;
        enum dma_data_direction         dma_dir;
        struct sg_table                 *dma_sgt;

        /* MMAP related */
        struct vb2_vmarea_handler       handler;
        atomic_t                        refcount;
        struct sg_table                 *sgt_base;

        /* USERPTR related */
        struct vm_area_struct           *vma;

        /* DMABUF related */
        struct dma_buf_attachment       *db_attach;
};

/*********************************************/
/*        scatterlist table functions        */
/*********************************************/


static void vb2_dc_sgt_foreach_page(struct sg_table *sgt,
        void (*cb)(struct page *pg))
{
        struct scatterlist *s;
        unsigned int i;

        for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
                struct page *page = sg_page(s);
                unsigned int n_pages = PAGE_ALIGN(s->offset + s->length)
                        >> PAGE_SHIFT;
                unsigned int j;

                for (j = 0; j < n_pages; ++j, ++page)
                        cb(page);
        }
}

static unsigned long vb2_dc_get_contiguous_size(struct sg_table *sgt)
{
        struct scatterlist *s;
        dma_addr_t expected = sg_dma_address(sgt->sgl);
        unsigned int i;
        unsigned long size = 0;

        for_each_sg(sgt->sgl, s, sgt->nents, i) {
                if (sg_dma_address(s) != expected)
                        break;
                expected = sg_dma_address(s) + sg_dma_len(s);
                size += sg_dma_len(s);
        }
        return size;
}

/*********************************************/
/*         callbacks for all buffers         */
/*********************************************/

static void *vb2_dc_cookie(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;

        return &buf->dma_addr;
}

static void *vb2_dc_vaddr(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;

        return buf->vaddr;
}

static unsigned int vb2_dc_num_users(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;

        return atomic_read(&buf->refcount);
}

static void vb2_dc_prepare(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;
        struct sg_table *sgt = buf->dma_sgt;

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

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

static void vb2_dc_finish(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;
        struct sg_table *sgt = buf->dma_sgt;

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

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

/*********************************************/
/*        callbacks for MMAP buffers         */
/*********************************************/

static void vb2_dc_put(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;

        if (!atomic_dec_and_test(&buf->refcount))
                return;

        if (buf->sgt_base) {
                sg_free_table(buf->sgt_base);
                kfree(buf->sgt_base);
        }
        dma_free_coherent(buf->dev, buf->size, buf->vaddr, buf->dma_addr);
        put_device(buf->dev);
        kfree(buf);
}

static void *vb2_dc_alloc(void *alloc_ctx, unsigned long size, gfp_t gfp_flags)
{
        struct vb2_dc_conf *conf = alloc_ctx;
        struct device *dev = conf->dev;
        struct vb2_dc_buf *buf;

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

        buf->vaddr = dma_alloc_coherent(dev, size, &buf->dma_addr,
                                                GFP_KERNEL | gfp_flags);
        if (!buf->vaddr) {
                dev_err(dev, "dma_alloc_coherent of size %ld failed\n", size);
                kfree(buf);
                return ERR_PTR(-ENOMEM);
        }

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

        buf->handler.refcount = &buf->refcount;
        buf->handler.put = vb2_dc_put;
        buf->handler.arg = buf;

        atomic_inc(&buf->refcount);

        return buf;
}

static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma)
{
        struct vb2_dc_buf *buf = buf_priv;
        int ret;

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

        /*
         * dma_mmap_* uses vm_pgoff as in-buffer offset, but we want to
         * map whole buffer
         */
        vma->vm_pgoff = 0;

        ret = dma_mmap_coherent(buf->dev, vma, buf->vaddr,
                buf->dma_addr, buf->size);

        if (ret) {
                pr_err("Remapping memory failed, error: %d\n", ret);
                return ret;
        }

        vma->vm_flags           |= VM_DONTEXPAND | VM_DONTDUMP;
        vma->vm_private_data    = &buf->handler;
        vma->vm_ops             = &vb2_common_vm_ops;

        vma->vm_ops->open(vma);

        pr_debug("%s: mapped dma addr 0x%08lx at 0x%08lx, size %ld\n",
                __func__, (unsigned long)buf->dma_addr, vma->vm_start,
                buf->size);

        return 0;
}

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

struct vb2_dc_attachment {
        struct sg_table sgt;
        enum dma_data_direction dir;
};

static int vb2_dc_dmabuf_ops_attach(struct dma_buf *dbuf, struct device *dev,
        struct dma_buf_attachment *dbuf_attach)
{
        struct vb2_dc_attachment *attach;
        unsigned int i;
        struct scatterlist *rd, *wr;
        struct sg_table *sgt;
        struct vb2_dc_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->sgt_base->orig_nents, GFP_KERNEL);
        if (ret) {
                kfree(attach);
                return -ENOMEM;
        }

        rd = buf->sgt_base->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->dir = DMA_NONE;
        dbuf_attach->priv = attach;

        return 0;
}

static void vb2_dc_dmabuf_ops_detach(struct dma_buf *dbuf,
        struct dma_buf_attachment *db_attach)
{
        struct vb2_dc_attachment *attach = db_attach->priv;
        struct sg_table *sgt;

        if (!attach)
                return;

        sgt = &attach->sgt;

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

static struct sg_table *vb2_dc_dmabuf_ops_map(
        struct dma_buf_attachment *db_attach, enum dma_data_direction dir)
{
        struct vb2_dc_attachment *attach = db_attach->priv;
        /* stealing dmabuf mutex to serialize map/unmap operations */
        struct mutex *lock = &db_attach->dmabuf->lock;
        struct sg_table *sgt;
        int ret;

        mutex_lock(lock);

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

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

        /* mapping to the client with new direction */
        ret = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents, dir);
        if (ret <= 0) {
                pr_err("failed to map scatterlist\n");
                mutex_unlock(lock);
                return ERR_PTR(-EIO);
        }

        attach->dir = dir;

        mutex_unlock(lock);

        return sgt;
}

static void vb2_dc_dmabuf_ops_unmap(struct dma_buf_attachment *db_attach,
        struct sg_table *sgt, enum dma_data_direction dir)
{
        /* nothing to be done here */
}

static void vb2_dc_dmabuf_ops_release(struct dma_buf *dbuf)
{
        /* drop reference obtained in vb2_dc_get_dmabuf */
        vb2_dc_put(dbuf->priv);
}

static void *vb2_dc_dmabuf_ops_kmap(struct dma_buf *dbuf, unsigned long pgnum)
{
        struct vb2_dc_buf *buf = dbuf->priv;

        return buf->vaddr + pgnum * PAGE_SIZE;
}

static void *vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf)
{
        struct vb2_dc_buf *buf = dbuf->priv;

        return buf->vaddr;
}

static int vb2_dc_dmabuf_ops_mmap(struct dma_buf *dbuf,
        struct vm_area_struct *vma)
{
        return vb2_dc_mmap(dbuf->priv, vma);
}

static struct dma_buf_ops vb2_dc_dmabuf_ops = {
        .attach = vb2_dc_dmabuf_ops_attach,
        .detach = vb2_dc_dmabuf_ops_detach,
        .map_dma_buf = vb2_dc_dmabuf_ops_map,
        .unmap_dma_buf = vb2_dc_dmabuf_ops_unmap,
        .kmap = vb2_dc_dmabuf_ops_kmap,
        .kmap_atomic = vb2_dc_dmabuf_ops_kmap,
        .vmap = vb2_dc_dmabuf_ops_vmap,
        .mmap = vb2_dc_dmabuf_ops_mmap,
        .release = vb2_dc_dmabuf_ops_release,
};

static struct sg_table *vb2_dc_get_base_sgt(struct vb2_dc_buf *buf)
{
        int ret;
        struct sg_table *sgt;

        sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
        if (!sgt) {
                dev_err(buf->dev, "failed to alloc sg table\n");
                return NULL;
        }

        ret = dma_get_sgtable(buf->dev, sgt, buf->vaddr, buf->dma_addr,
                buf->size);
        if (ret < 0) {
                dev_err(buf->dev, "failed to get scatterlist from DMA API\n");
                kfree(sgt);
                return NULL;
        }

        return sgt;
}

static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;
        struct dma_buf *dbuf;

        if (!buf->sgt_base)
                buf->sgt_base = vb2_dc_get_base_sgt(buf);

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

        dbuf = dma_buf_export(buf, &vb2_dc_dmabuf_ops, buf->size, 0);
        if (IS_ERR(dbuf))
                return NULL;

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

        return dbuf;
}

/*********************************************/
/*       callbacks for USERPTR buffers       */
/*********************************************/

static inline int vma_is_io(struct vm_area_struct *vma)
{
        return !!(vma->vm_flags & (VM_IO | VM_PFNMAP));
}

static int vb2_dc_get_user_pages(unsigned long start, struct page **pages,
        int n_pages, struct vm_area_struct *vma, int write)
{
        if (vma_is_io(vma)) {
                unsigned int i;

                for (i = 0; i < n_pages; ++i, start += PAGE_SIZE) {
                        unsigned long pfn;
                        int ret = follow_pfn(vma, start, &pfn);

                        if (ret) {
                                pr_err("no page for address %lu\n", start);
                                return ret;
                        }
                        pages[i] = pfn_to_page(pfn);
                }
        } else {
                int n;

                n = get_user_pages(current, current->mm, start & PAGE_MASK,
                        n_pages, write, 1, pages, NULL);
                /* negative error means that no page was pinned */
                n = max(n, 0);
                if (n != n_pages) {
                        pr_err("got only %d of %d user pages\n", n, n_pages);
                        while (n)
                                put_page(pages[--n]);
                        return -EFAULT;
                }
        }

        return 0;
}

static void vb2_dc_put_dirty_page(struct page *page)
{
        set_page_dirty_lock(page);
        put_page(page);
}

static void vb2_dc_put_userptr(void *buf_priv)
{
        struct vb2_dc_buf *buf = buf_priv;
        struct sg_table *sgt = buf->dma_sgt;

        dma_unmap_sg(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
        if (!vma_is_io(buf->vma))
                vb2_dc_sgt_foreach_page(sgt, vb2_dc_put_dirty_page);

        sg_free_table(sgt);
        kfree(sgt);
        vb2_put_vma(buf->vma);
        kfree(buf);
}

static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
        unsigned long size, int write)
{
        struct vb2_dc_conf *conf = alloc_ctx;
        struct vb2_dc_buf *buf;
        unsigned long start;
        unsigned long end;
        unsigned long offset;
        struct page **pages;
        int n_pages;
        int ret = 0;
        struct vm_area_struct *vma;
        struct sg_table *sgt;
        unsigned long contig_size;
        unsigned long dma_align = dma_get_cache_alignment();

        /* Only cache aligned DMA transfers are reliable */
        if (!IS_ALIGNED(vaddr | size, dma_align)) {
                pr_debug("user data must be aligned to %lu bytes\n", dma_align);
                return ERR_PTR(-EINVAL);
        }

        if (!size) {
                pr_debug("size is zero\n");
                return ERR_PTR(-EINVAL);
        }

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

        buf->dev = conf->dev;
        buf->dma_dir = write ? DMA_FROM_DEVICE : DMA_TO_DEVICE;

        start = vaddr & PAGE_MASK;
        offset = vaddr & ~PAGE_MASK;
        end = PAGE_ALIGN(vaddr + size);
        n_pages = (end - start) >> PAGE_SHIFT;

        pages = kmalloc(n_pages * sizeof(pages[0]), GFP_KERNEL);
        if (!pages) {
                ret = -ENOMEM;
                pr_err("failed to allocate pages table\n");
                goto fail_buf;
        }

        /* current->mm->mmap_sem is taken by videobuf2 core */
        vma = find_vma(current->mm, vaddr);
        if (!vma) {
                pr_err("no vma for address %lu\n", vaddr);
                ret = -EFAULT;
                goto fail_pages;
        }

        if (vma->vm_end < vaddr + size) {
                pr_err("vma at %lu is too small for %lu bytes\n", vaddr, size);
                ret = -EFAULT;
                goto fail_pages;
        }

        buf->vma = vb2_get_vma(vma);
        if (!buf->vma) {
                pr_err("failed to copy vma\n");
                ret = -ENOMEM;
                goto fail_pages;
        }

        /* extract page list from userspace mapping */
        ret = vb2_dc_get_user_pages(start, pages, n_pages, vma, write);
        if (ret) {
                pr_err("failed to get user pages\n");
                goto fail_vma;
        }

        sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
        if (!sgt) {
                pr_err("failed to allocate sg table\n");
                ret = -ENOMEM;
                goto fail_get_user_pages;
        }

        ret = sg_alloc_table_from_pages(sgt, pages, n_pages,
                offset, size, GFP_KERNEL);
        if (ret) {
                pr_err("failed to initialize sg table\n");
                goto fail_sgt;
        }

        /* pages are no longer needed */
        kfree(pages);
        pages = NULL;

        sgt->nents = dma_map_sg(buf->dev, sgt->sgl, sgt->orig_nents,
                buf->dma_dir);
        if (sgt->nents <= 0) {
                pr_err("failed to map scatterlist\n");
                ret = -EIO;
                goto fail_sgt_init;
        }

        contig_size = vb2_dc_get_contiguous_size(sgt);
        if (contig_size < size) {
                pr_err("contiguous mapping is too small %lu/%lu\n",
                        contig_size, size);
                ret = -EFAULT;
                goto fail_map_sg;
        }

        buf->dma_addr = sg_dma_address(sgt->sgl);
        buf->size = size;
        buf->dma_sgt = sgt;

        return buf;

fail_map_sg:
        dma_unmap_sg(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);

fail_sgt_init:
        if (!vma_is_io(buf->vma))
                vb2_dc_sgt_foreach_page(sgt, put_page);
        sg_free_table(sgt);

fail_sgt:
        kfree(sgt);

fail_get_user_pages:
        if (pages && !vma_is_io(buf->vma))
                while (n_pages)
                        put_page(pages[--n_pages]);

fail_vma:
        vb2_put_vma(buf->vma);

fail_pages:
        kfree(pages); /* kfree is NULL-proof */

fail_buf:
        kfree(buf);

        return ERR_PTR(ret);
}

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

static int vb2_dc_map_dmabuf(void *mem_priv)
{
        struct vb2_dc_buf *buf = mem_priv;
        struct sg_table *sgt;
        unsigned long contig_size;

        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_OR_NULL(sgt)) {
                pr_err("Error getting dmabuf scatterlist\n");
                return -EINVAL;
        }

        /* checking if dmabuf is big enough to store contiguous chunk */
        contig_size = vb2_dc_get_contiguous_size(sgt);
        if (contig_size < buf->size) {
                pr_err("contiguous chunk is too small %lu/%lu b\n",
                        contig_size, buf->size);
                dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);
                return -EFAULT;
        }

        buf->dma_addr = sg_dma_address(sgt->sgl);
        buf->dma_sgt = sgt;

        return 0;
}

static void vb2_dc_unmap_dmabuf(void *mem_priv)
{
        struct vb2_dc_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;
        }

        dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);

        buf->dma_addr = 0;
        buf->dma_sgt = NULL;
}

static void vb2_dc_detach_dmabuf(void *mem_priv)
{
        struct vb2_dc_buf *buf = mem_priv;

        /* if vb2 works correctly you should never detach mapped buffer */
        if (WARN_ON(buf->dma_addr))
                vb2_dc_unmap_dmabuf(buf);

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

static void *vb2_dc_attach_dmabuf(void *alloc_ctx, struct dma_buf *dbuf,
        unsigned long size, int write)
{
        struct vb2_dc_conf *conf = alloc_ctx;
        struct vb2_dc_buf *buf;
        struct dma_buf_attachment *dba;

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

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

        buf->dev = conf->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 = write ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
        buf->size = size;
        buf->db_attach = dba;

        return buf;
}

/*********************************************/
/*       DMA CONTIG exported functions       */
/*********************************************/

const struct vb2_mem_ops vb2_dma_contig_memops = {
        .alloc          = vb2_dc_alloc,
        .put            = vb2_dc_put,
        .get_dmabuf     = vb2_dc_get_dmabuf,
        .cookie         = vb2_dc_cookie,
        .vaddr          = vb2_dc_vaddr,
        .mmap           = vb2_dc_mmap,
        .get_userptr    = vb2_dc_get_userptr,
        .put_userptr    = vb2_dc_put_userptr,
        .prepare        = vb2_dc_prepare,
        .finish         = vb2_dc_finish,
        .map_dmabuf     = vb2_dc_map_dmabuf,
        .unmap_dmabuf   = vb2_dc_unmap_dmabuf,
        .attach_dmabuf  = vb2_dc_attach_dmabuf,
        .detach_dmabuf  = vb2_dc_detach_dmabuf,
        .num_users      = vb2_dc_num_users,
};
EXPORT_SYMBOL_GPL(vb2_dma_contig_memops);

void *vb2_dma_contig_init_ctx(struct device *dev)
{
        struct vb2_dc_conf *conf;

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

        conf->dev = dev;

        return conf;
}
EXPORT_SYMBOL_GPL(vb2_dma_contig_init_ctx);

void vb2_dma_contig_cleanup_ctx(void *alloc_ctx)
{
        kfree(alloc_ctx);
}
EXPORT_SYMBOL_GPL(vb2_dma_contig_cleanup_ctx);

MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2");
MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
MODULE_LICENSE("GPL");