diff mbox series

[v4,4/4] dma-buf: heaps: add chunk heap to dmabuf heaps

Message ID 20210121175502.274391-5-minchan@kernel.org (mailing list archive)
State New
Headers show
Series Chunk Heap Support on DMA-HEAP | expand

Commit Message

Minchan Kim Jan. 21, 2021, 5:55 p.m. UTC
From: Hyesoo Yu <hyesoo.yu@samsung.com>

This patch supports chunk heap that allocates the buffers that
arranged into a list a fixed size chunks taken from CMA.

The chunk heap driver is bound directly to a reserved_memory
node by following Rob Herring's suggestion in [1].

[1] https://lore.kernel.org/lkml/20191025225009.50305-2-john.stultz@linaro.org/T/#m3dc63acd33fea269a584f43bb799a876f0b2b45d

Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Hyesoo Yu <hyesoo.yu@samsung.com>
Signed-off-by: Hridya Valsaraju <hridya@google.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
 drivers/dma-buf/heaps/Kconfig      |   8 +
 drivers/dma-buf/heaps/Makefile     |   1 +
 drivers/dma-buf/heaps/chunk_heap.c | 492 +++++++++++++++++++++++++++++
 3 files changed, 501 insertions(+)
 create mode 100644 drivers/dma-buf/heaps/chunk_heap.c

Comments

Christoph Hellwig Jan. 26, 2021, 7:07 a.m. UTC | #1
> +config DMABUF_HEAPS_CHUNK
> +	bool "DMA-BUF CHUNK Heap"
> +	depends on DMABUF_HEAPS && DMA_CMA
> +	help
> +	  Choose this option to enable dma-buf CHUNK heap. This heap is backed
> +	  by the Contiguous Memory Allocator (CMA) and allocates the buffers that
> +	  are arranged into a list of fixed size chunks taken from CMA.

Overly long line, which in text flowing text is really, really annoying.

Many more later.  Remember that > 80 chars are only allowed if they
significantly improve readability.
John Stultz Jan. 26, 2021, 7:32 a.m. UTC | #2
On Thu, Jan 21, 2021 at 9:55 AM Minchan Kim <minchan@kernel.org> wrote:

Hey Minchan,
  Thanks for sending this out! I'm still working through testing with
this patch set, so I may have some more feedback tomorrow, but a few
quick items I did hit below.

> +
> +#define CHUNK_PREFIX "chunk-"
> +
> +static int register_chunk_heap(struct chunk_heap *chunk_heap_info)
> +{
> +       struct dma_heap_export_info exp_info;
> +       const char *name = cma_get_name(chunk_heap_info->cma);
> +       size_t len = strlen(CHUNK_PREFIX) + strlen(name) + 1;
> +       char *buf = kmalloc(len, GFP_KERNEL);
> +
> +       if (!buf)
> +               return -ENOMEM;
> +
> +       sprintf(buf, CHUNK_PREFIX"%s", cma_get_name(chunk_heap_info->cma));
> +       buf[len] = '\0';
> +
> +       exp_info.name = buf;
> +       exp_info.name = cma_get_name(chunk_heap_info->cma);

I think you intended to delete this line, as it's overwriting your
prefixed name.

> +       exp_info.ops = &chunk_heap_ops;
> +       exp_info.priv = chunk_heap_info;
> +
> +       chunk_heap_info->heap = dma_heap_add(&exp_info);
> +       if (IS_ERR(chunk_heap_info->heap)) {
> +               kfree(buf);
> +               return PTR_ERR(chunk_heap_info->heap);
> +       }
> +
> +       return 0;
> +}
> +
> +static int __init chunk_heap_init(void)
> +{
> +       unsigned int i;
> +
> +       for (i = 0; i < chunk_heap_count; i++)
> +               register_chunk_heap(&chunk_heaps[i]);
> +
> +       return 0;
> +}
> +module_init(chunk_heap_init);
> +
> +#ifdef CONFIG_OF_EARLY_FLATTREE
> +
> +static int __init dmabuf_chunk_heap_area_init(struct reserved_mem *rmem)
> +{
> +       int ret;
> +       struct cma *cma;
> +       struct chunk_heap *chunk_heap_info;
> +       const __be32 *chunk_order;
> +
> +       phys_addr_t align = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
> +       phys_addr_t mask = align - 1;
> +
> +       if ((rmem->base & mask) || (rmem->size & mask)) {
> +               pr_err("Incorrect alignment for CMA region\n");
> +               return -EINVAL;

Passing this check can be tough if you're using dynamically assigned
rmem, so it might be helpful for debugging to print the base/size/mask
values?

thanks
-john
Michal Hocko Jan. 26, 2021, 7:46 a.m. UTC | #3
On Thu 21-01-21 09:55:02, Minchan Kim wrote:
> From: Hyesoo Yu <hyesoo.yu@samsung.com>
> 
> This patch supports chunk heap that allocates the buffers that
> arranged into a list a fixed size chunks taken from CMA.
> 
> The chunk heap driver is bound directly to a reserved_memory
> node by following Rob Herring's suggestion in [1].
> 
> [1] https://lore.kernel.org/lkml/20191025225009.50305-2-john.stultz@linaro.org/T/#m3dc63acd33fea269a584f43bb799a876f0b2b45d

Who is using this allocator in the kernel?
Minchan Kim Jan. 26, 2021, 7:24 p.m. UTC | #4
On Mon, Jan 25, 2021 at 11:32:57PM -0800, John Stultz wrote:
> On Thu, Jan 21, 2021 at 9:55 AM Minchan Kim <minchan@kernel.org> wrote:
> 
> Hey Minchan,
>   Thanks for sending this out! I'm still working through testing with
> this patch set, so I may have some more feedback tomorrow, but a few
> quick items I did hit below.
> 
> > +
> > +#define CHUNK_PREFIX "chunk-"
> > +
> > +static int register_chunk_heap(struct chunk_heap *chunk_heap_info)
> > +{
> > +       struct dma_heap_export_info exp_info;
> > +       const char *name = cma_get_name(chunk_heap_info->cma);
> > +       size_t len = strlen(CHUNK_PREFIX) + strlen(name) + 1;
> > +       char *buf = kmalloc(len, GFP_KERNEL);
> > +
> > +       if (!buf)
> > +               return -ENOMEM;
> > +
> > +       sprintf(buf, CHUNK_PREFIX"%s", cma_get_name(chunk_heap_info->cma));
> > +       buf[len] = '\0';
> > +
> > +       exp_info.name = buf;
> > +       exp_info.name = cma_get_name(chunk_heap_info->cma);
> 
> I think you intended to delete this line, as it's overwriting your
> prefixed name.

Hi John,

You're right. Will fix it.

> 
> > +       exp_info.ops = &chunk_heap_ops;
> > +       exp_info.priv = chunk_heap_info;
> > +
> > +       chunk_heap_info->heap = dma_heap_add(&exp_info);
> > +       if (IS_ERR(chunk_heap_info->heap)) {
> > +               kfree(buf);
> > +               return PTR_ERR(chunk_heap_info->heap);
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static int __init chunk_heap_init(void)
> > +{
> > +       unsigned int i;
> > +
> > +       for (i = 0; i < chunk_heap_count; i++)
> > +               register_chunk_heap(&chunk_heaps[i]);
> > +
> > +       return 0;
> > +}
> > +module_init(chunk_heap_init);
> > +
> > +#ifdef CONFIG_OF_EARLY_FLATTREE
> > +
> > +static int __init dmabuf_chunk_heap_area_init(struct reserved_mem *rmem)
> > +{
> > +       int ret;
> > +       struct cma *cma;
> > +       struct chunk_heap *chunk_heap_info;
> > +       const __be32 *chunk_order;
> > +
> > +       phys_addr_t align = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
> > +       phys_addr_t mask = align - 1;
> > +
> > +       if ((rmem->base & mask) || (rmem->size & mask)) {
> > +               pr_err("Incorrect alignment for CMA region\n");
> > +               return -EINVAL;
> 
> Passing this check can be tough if you're using dynamically assigned
> rmem, so it might be helpful for debugging to print the base/size/mask
> values?

Let me fold this into next respin.

diff --git a/drivers/dma-buf/heaps/chunk_heap.c b/drivers/dma-buf/heaps/chunk_heap.c
index 6fe8e69d108f..cc2ed5341b54 100644
--- a/drivers/dma-buf/heaps/chunk_heap.c
+++ b/drivers/dma-buf/heaps/chunk_heap.c
@@ -456,7 +456,8 @@ static int __init dmabuf_chunk_heap_area_init(struct reserved_mem *rmem)
        phys_addr_t mask = align - 1;

        if ((rmem->base & mask) || (rmem->size & mask)) {
-               pr_err("Incorrect alignment for CMA region\n");
+               pr_err("Incorrect alignment for CMA region: base %pa size %pa mask %pa\n",
+                               rmem->base, rmem->size, mask);
                return -EINVAL;
        }

Thanks for the review, John!
Minchan Kim Jan. 26, 2021, 7:25 p.m. UTC | #5
On Tue, Jan 26, 2021 at 08:46:05AM +0100, Michal Hocko wrote:
> On Thu 21-01-21 09:55:02, Minchan Kim wrote:
> > From: Hyesoo Yu <hyesoo.yu@samsung.com>
> > 
> > This patch supports chunk heap that allocates the buffers that
> > arranged into a list a fixed size chunks taken from CMA.
> > 
> > The chunk heap driver is bound directly to a reserved_memory
> > node by following Rob Herring's suggestion in [1].
> > 
> > [1] https://lore.kernel.org/lkml/20191025225009.50305-2-john.stultz@linaro.org/T/#m3dc63acd33fea269a584f43bb799a876f0b2b45d
> 
> Who is using this allocator in the kernel?

Userspace uses the memory via mapping it via dmabuf.
Minchan Kim Jan. 26, 2021, 7:27 p.m. UTC | #6
On Tue, Jan 26, 2021 at 07:07:44AM +0000, Christoph Hellwig wrote:
> > +config DMABUF_HEAPS_CHUNK
> > +	bool "DMA-BUF CHUNK Heap"
> > +	depends on DMABUF_HEAPS && DMA_CMA
> > +	help
> > +	  Choose this option to enable dma-buf CHUNK heap. This heap is backed
> > +	  by the Contiguous Memory Allocator (CMA) and allocates the buffers that
> > +	  are arranged into a list of fixed size chunks taken from CMA.
> 
> Overly long line, which in text flowing text is really, really annoying.
> 
> Many more later.  Remember that > 80 chars are only allowed if they
> significantly improve readability.  

Let me make it shorter than 80 chars in next revision.
Thanks for the reivew, Christoph.
Michal Hocko Jan. 27, 2021, 8:09 a.m. UTC | #7
On Tue 26-01-21 11:25:36, Minchan Kim wrote:
> On Tue, Jan 26, 2021 at 08:46:05AM +0100, Michal Hocko wrote:
> > On Thu 21-01-21 09:55:02, Minchan Kim wrote:
> > > From: Hyesoo Yu <hyesoo.yu@samsung.com>
> > > 
> > > This patch supports chunk heap that allocates the buffers that
> > > arranged into a list a fixed size chunks taken from CMA.
> > > 
> > > The chunk heap driver is bound directly to a reserved_memory
> > > node by following Rob Herring's suggestion in [1].
> > > 
> > > [1] https://lore.kernel.org/lkml/20191025225009.50305-2-john.stultz@linaro.org/T/#m3dc63acd33fea269a584f43bb799a876f0b2b45d
> > 
> > Who is using this allocator in the kernel?
> 
> Userspace uses the memory via mapping it via dmabuf.

Ohh, I see. I thought this was an interface to consume in the kernel.
Thanks for the clarification!
diff mbox series

Patch

diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
index a5eef06c4226..e9595e26f831 100644
--- a/drivers/dma-buf/heaps/Kconfig
+++ b/drivers/dma-buf/heaps/Kconfig
@@ -12,3 +12,11 @@  config DMABUF_HEAPS_CMA
 	  Choose this option to enable dma-buf CMA heap. This heap is backed
 	  by the Contiguous Memory Allocator (CMA). If your system has these
 	  regions, you should say Y here.
+
+config DMABUF_HEAPS_CHUNK
+	bool "DMA-BUF CHUNK Heap"
+	depends on DMABUF_HEAPS && DMA_CMA
+	help
+	  Choose this option to enable dma-buf CHUNK heap. This heap is backed
+	  by the Contiguous Memory Allocator (CMA) and allocates the buffers that
+	  are arranged into a list of fixed size chunks taken from CMA.
diff --git a/drivers/dma-buf/heaps/Makefile b/drivers/dma-buf/heaps/Makefile
index 974467791032..8faa6cfdc0c5 100644
--- a/drivers/dma-buf/heaps/Makefile
+++ b/drivers/dma-buf/heaps/Makefile
@@ -1,3 +1,4 @@ 
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_DMABUF_HEAPS_SYSTEM)	+= system_heap.o
 obj-$(CONFIG_DMABUF_HEAPS_CMA)		+= cma_heap.o
+obj-$(CONFIG_DMABUF_HEAPS_CHUNK)	+= chunk_heap.o
diff --git a/drivers/dma-buf/heaps/chunk_heap.c b/drivers/dma-buf/heaps/chunk_heap.c
new file mode 100644
index 000000000000..15df42acee4b
--- /dev/null
+++ b/drivers/dma-buf/heaps/chunk_heap.c
@@ -0,0 +1,492 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DMA-BUF chunk heap exporter
+ *
+ * Copyright (c) 2020 Samsung Electronics Co., Ltd.
+ * Author: <hyesoo.yu@samsung.com> for Samsung Electronics.
+ */
+
+#include <linux/cma.h>
+#include <linux/device.h>
+#include <linux/dma-buf.h>
+#include <linux/dma-heap.h>
+#include <linux/dma-mapping.h>
+#include <linux/dma-map-ops.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/highmem.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/scatterlist.h>
+#include <linux/sched/signal.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+struct chunk_heap {
+	struct dma_heap *heap;
+	uint32_t order;
+	struct cma *cma;
+};
+
+struct chunk_heap_buffer {
+	struct chunk_heap *heap;
+	struct list_head attachments;
+	struct mutex lock;
+	struct sg_table sg_table;
+	unsigned long len;
+	int vmap_cnt;
+	void *vaddr;
+};
+
+struct chunk_heap_attachment {
+	struct device *dev;
+	struct sg_table *table;
+	struct list_head list;
+	bool mapped;
+};
+
+struct chunk_heap chunk_heaps[MAX_CMA_AREAS];
+unsigned int chunk_heap_count;
+
+static struct sg_table *dup_sg_table(struct sg_table *table)
+{
+	struct sg_table *new_table;
+	int ret, i;
+	struct scatterlist *sg, *new_sg;
+
+	new_table = kzalloc(sizeof(*new_table), GFP_KERNEL);
+	if (!new_table)
+		return ERR_PTR(-ENOMEM);
+
+	ret = sg_alloc_table(new_table, table->orig_nents, GFP_KERNEL);
+	if (ret) {
+		kfree(new_table);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	new_sg = new_table->sgl;
+	for_each_sgtable_sg(table, sg, i) {
+		sg_set_page(new_sg, sg_page(sg), sg->length, sg->offset);
+		new_sg = sg_next(new_sg);
+	}
+
+	return new_table;
+}
+
+static int chunk_heap_attach(struct dma_buf *dmabuf, struct dma_buf_attachment *attachment)
+{
+	struct chunk_heap_buffer *buffer = dmabuf->priv;
+	struct chunk_heap_attachment *a;
+	struct sg_table *table;
+
+	a = kzalloc(sizeof(*a), GFP_KERNEL);
+	if (!a)
+		return -ENOMEM;
+
+	table = dup_sg_table(&buffer->sg_table);
+	if (IS_ERR(table)) {
+		kfree(a);
+		return -ENOMEM;
+	}
+
+	a->table = table;
+	a->dev = attachment->dev;
+
+	attachment->priv = a;
+
+	mutex_lock(&buffer->lock);
+	list_add(&a->list, &buffer->attachments);
+	mutex_unlock(&buffer->lock);
+
+	return 0;
+}
+
+static void chunk_heap_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attachment)
+{
+	struct chunk_heap_buffer *buffer = dmabuf->priv;
+	struct chunk_heap_attachment *a = attachment->priv;
+
+	mutex_lock(&buffer->lock);
+	list_del(&a->list);
+	mutex_unlock(&buffer->lock);
+
+	sg_free_table(a->table);
+	kfree(a->table);
+	kfree(a);
+}
+
+static struct sg_table *chunk_heap_map_dma_buf(struct dma_buf_attachment *attachment,
+					       enum dma_data_direction direction)
+{
+	struct chunk_heap_attachment *a = attachment->priv;
+	struct sg_table *table = a->table;
+	int ret;
+
+	if (a->mapped)
+		return table;
+
+	ret = dma_map_sgtable(attachment->dev, table, direction, 0);
+	if (ret)
+		return ERR_PTR(ret);
+
+	a->mapped = true;
+	return table;
+}
+
+static void chunk_heap_unmap_dma_buf(struct dma_buf_attachment *attachment,
+				     struct sg_table *table,
+				     enum dma_data_direction direction)
+{
+	struct chunk_heap_attachment *a = attachment->priv;
+
+	a->mapped = false;
+	dma_unmap_sgtable(attachment->dev, table, direction, 0);
+}
+
+static int chunk_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
+						enum dma_data_direction direction)
+{
+	struct chunk_heap_buffer *buffer = dmabuf->priv;
+	struct chunk_heap_attachment *a;
+
+	mutex_lock(&buffer->lock);
+
+	if (buffer->vmap_cnt)
+		invalidate_kernel_vmap_range(buffer->vaddr, buffer->len);
+
+	list_for_each_entry(a, &buffer->attachments, list) {
+		if (!a->mapped)
+			continue;
+		dma_sync_sgtable_for_cpu(a->dev, a->table, direction);
+	}
+	mutex_unlock(&buffer->lock);
+
+	return 0;
+}
+
+static int chunk_heap_dma_buf_end_cpu_access(struct dma_buf *dmabuf,
+					      enum dma_data_direction direction)
+{
+	struct chunk_heap_buffer *buffer = dmabuf->priv;
+	struct chunk_heap_attachment *a;
+
+	mutex_lock(&buffer->lock);
+
+	if (buffer->vmap_cnt)
+		flush_kernel_vmap_range(buffer->vaddr, buffer->len);
+
+	list_for_each_entry(a, &buffer->attachments, list) {
+		if (!a->mapped)
+			continue;
+		dma_sync_sgtable_for_device(a->dev, a->table, direction);
+	}
+	mutex_unlock(&buffer->lock);
+
+	return 0;
+}
+
+static int chunk_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
+{
+	struct chunk_heap_buffer *buffer = dmabuf->priv;
+	struct sg_table *table = &buffer->sg_table;
+	unsigned long addr = vma->vm_start;
+	struct sg_page_iter piter;
+	int ret;
+
+	for_each_sgtable_page(table, &piter, vma->vm_pgoff) {
+		struct page *page = sg_page_iter_page(&piter);
+
+		ret = remap_pfn_range(vma, addr, page_to_pfn(page), PAGE_SIZE,
+				      vma->vm_page_prot);
+		if (ret)
+			return ret;
+		addr += PAGE_SIZE;
+		if (addr >= vma->vm_end)
+			return 0;
+	}
+	return 0;
+}
+
+static void *chunk_heap_do_vmap(struct chunk_heap_buffer *buffer)
+{
+	struct sg_table *table = &buffer->sg_table;
+	int npages = PAGE_ALIGN(buffer->len) / PAGE_SIZE;
+	struct page **pages = vmalloc(sizeof(struct page *) * npages);
+	struct page **tmp = pages;
+	struct sg_page_iter piter;
+	void *vaddr;
+
+	if (!pages)
+		return ERR_PTR(-ENOMEM);
+
+	for_each_sgtable_page(table, &piter, 0) {
+		WARN_ON(tmp - pages >= npages);
+		*tmp++ = sg_page_iter_page(&piter);
+	}
+
+	vaddr = vmap(pages, npages, VM_MAP, PAGE_KERNEL);
+	vfree(pages);
+
+	if (!vaddr)
+		return ERR_PTR(-ENOMEM);
+
+	return vaddr;
+}
+
+static int chunk_heap_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
+{
+	struct chunk_heap_buffer *buffer = dmabuf->priv;
+	void *vaddr;
+
+	mutex_lock(&buffer->lock);
+	if (buffer->vmap_cnt) {
+		vaddr = buffer->vaddr;
+	} else {
+		vaddr = chunk_heap_do_vmap(buffer);
+		if (IS_ERR(vaddr)) {
+			mutex_unlock(&buffer->lock);
+
+			return PTR_ERR(vaddr);
+		}
+		buffer->vaddr = vaddr;
+	}
+	buffer->vmap_cnt++;
+	dma_buf_map_set_vaddr(map, vaddr);
+
+	mutex_unlock(&buffer->lock);
+
+	return 0;
+}
+
+static void chunk_heap_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
+{
+	struct chunk_heap_buffer *buffer = dmabuf->priv;
+
+	mutex_lock(&buffer->lock);
+	if (!--buffer->vmap_cnt) {
+		vunmap(buffer->vaddr);
+		buffer->vaddr = NULL;
+	}
+	mutex_unlock(&buffer->lock);
+}
+
+static void chunk_heap_dma_buf_release(struct dma_buf *dmabuf)
+{
+	struct chunk_heap_buffer *buffer = dmabuf->priv;
+	struct chunk_heap *chunk_heap = buffer->heap;
+	struct sg_table *table;
+	struct scatterlist *sg;
+	int i;
+
+	table = &buffer->sg_table;
+	for_each_sgtable_sg(table, sg, i)
+		cma_release(chunk_heap->cma, sg_page(sg), 1 << chunk_heap->order);
+	sg_free_table(table);
+	kfree(buffer);
+}
+
+static const struct dma_buf_ops chunk_heap_buf_ops = {
+	.attach = chunk_heap_attach,
+	.detach = chunk_heap_detach,
+	.map_dma_buf = chunk_heap_map_dma_buf,
+	.unmap_dma_buf = chunk_heap_unmap_dma_buf,
+	.begin_cpu_access = chunk_heap_dma_buf_begin_cpu_access,
+	.end_cpu_access = chunk_heap_dma_buf_end_cpu_access,
+	.mmap = chunk_heap_mmap,
+	.vmap = chunk_heap_vmap,
+	.vunmap = chunk_heap_vunmap,
+	.release = chunk_heap_dma_buf_release,
+};
+
+static int chunk_heap_allocate(struct dma_heap *heap, unsigned long len,
+			       unsigned long fd_flags, unsigned long heap_flags)
+{
+	struct chunk_heap *chunk_heap = dma_heap_get_drvdata(heap);
+	struct chunk_heap_buffer *buffer;
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+	struct dma_buf *dmabuf;
+	struct sg_table *table;
+	struct scatterlist *sg;
+	struct page **pages;
+	unsigned int chunk_size = PAGE_SIZE << chunk_heap->order;
+	unsigned int count, alloced = 0;
+	unsigned int alloc_order = max_t(unsigned int, pageblock_order, chunk_heap->order);
+	unsigned int nr_chunks_per_alloc = 1 << (alloc_order - chunk_heap->order);
+	gfp_t gfp_flags = GFP_KERNEL|__GFP_NORETRY;
+	int ret = -ENOMEM;
+	pgoff_t pg;
+
+	buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
+	if (!buffer)
+		return ret;
+
+	INIT_LIST_HEAD(&buffer->attachments);
+	mutex_init(&buffer->lock);
+	buffer->heap = chunk_heap;
+	buffer->len = ALIGN(len, chunk_size);
+	count = buffer->len / chunk_size;
+
+	pages = kvmalloc_array(count, sizeof(*pages), GFP_KERNEL);
+	if (!pages)
+		goto err_pages;
+
+	while (alloced < count) {
+		struct page *page;
+		int i;
+
+		while (count - alloced < nr_chunks_per_alloc) {
+			alloc_order--;
+			nr_chunks_per_alloc >>= 1;
+		}
+
+		page = cma_alloc(chunk_heap->cma, 1 << alloc_order,
+					alloc_order, gfp_flags);
+		if (!page) {
+			if (gfp_flags & __GFP_NORETRY) {
+				gfp_flags &= ~__GFP_NORETRY;
+				continue;
+			}
+			break;
+		}
+
+		for (i = 0; i < nr_chunks_per_alloc; i++, alloced++) {
+			pages[alloced] = page;
+			page += 1 << chunk_heap->order;
+		}
+	}
+
+	if (alloced < count)
+		goto err_alloc;
+
+	table = &buffer->sg_table;
+	if (sg_alloc_table(table, count, GFP_KERNEL))
+		goto err_alloc;
+
+	sg = table->sgl;
+	for (pg = 0; pg < count; pg++) {
+		sg_set_page(sg, pages[pg], chunk_size, 0);
+		sg = sg_next(sg);
+	}
+
+	exp_info.ops = &chunk_heap_buf_ops;
+	exp_info.size = buffer->len;
+	exp_info.flags = fd_flags;
+	exp_info.priv = buffer;
+	dmabuf = dma_buf_export(&exp_info);
+	if (IS_ERR(dmabuf)) {
+		ret = PTR_ERR(dmabuf);
+		goto err_export;
+	}
+	kvfree(pages);
+
+	ret = dma_buf_fd(dmabuf, fd_flags);
+	if (ret < 0) {
+		dma_buf_put(dmabuf);
+		return ret;
+	}
+
+	return 0;
+err_export:
+	sg_free_table(table);
+err_alloc:
+	for (pg = 0; pg < alloced; pg++)
+		cma_release(chunk_heap->cma, pages[pg], 1 << chunk_heap->order);
+	kvfree(pages);
+err_pages:
+	kfree(buffer);
+
+	return ret;
+}
+
+static const struct dma_heap_ops chunk_heap_ops = {
+	.allocate = chunk_heap_allocate,
+};
+
+#define CHUNK_PREFIX "chunk-"
+
+static int register_chunk_heap(struct chunk_heap *chunk_heap_info)
+{
+	struct dma_heap_export_info exp_info;
+	const char *name = cma_get_name(chunk_heap_info->cma);
+	size_t len = strlen(CHUNK_PREFIX) + strlen(name) + 1;
+	char *buf = kmalloc(len, GFP_KERNEL);
+
+	if (!buf)
+		return -ENOMEM;
+
+	sprintf(buf, CHUNK_PREFIX"%s", cma_get_name(chunk_heap_info->cma));
+	buf[len] = '\0';
+
+	exp_info.name = buf;
+	exp_info.name = cma_get_name(chunk_heap_info->cma);
+	exp_info.ops = &chunk_heap_ops;
+	exp_info.priv = chunk_heap_info;
+
+	chunk_heap_info->heap = dma_heap_add(&exp_info);
+	if (IS_ERR(chunk_heap_info->heap)) {
+		kfree(buf);
+		return PTR_ERR(chunk_heap_info->heap);
+	}
+
+	return 0;
+}
+
+static int __init chunk_heap_init(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < chunk_heap_count; i++)
+		register_chunk_heap(&chunk_heaps[i]);
+
+	return 0;
+}
+module_init(chunk_heap_init);
+
+#ifdef CONFIG_OF_EARLY_FLATTREE
+
+static int __init dmabuf_chunk_heap_area_init(struct reserved_mem *rmem)
+{
+	int ret;
+	struct cma *cma;
+	struct chunk_heap *chunk_heap_info;
+	const __be32 *chunk_order;
+
+	phys_addr_t align = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
+	phys_addr_t mask = align - 1;
+
+	if ((rmem->base & mask) || (rmem->size & mask)) {
+		pr_err("Incorrect alignment for CMA region\n");
+		return -EINVAL;
+	}
+
+	ret = cma_init_reserved_mem(rmem->base, rmem->size, 0, rmem->name, &cma);
+	if (ret) {
+		pr_err("Reserved memory: unable to setup CMA region\n");
+		return ret;
+	}
+
+	/* Architecture specific contiguous memory fixup. */
+	dma_contiguous_early_fixup(rmem->base, rmem->size);
+
+	chunk_heap_info = &chunk_heaps[chunk_heap_count];
+	chunk_heap_info->cma = cma;
+
+	chunk_order = of_get_flat_dt_prop(rmem->fdt_node, "chunk-order", NULL);
+
+	if (chunk_order)
+		chunk_heap_info->order = be32_to_cpu(*chunk_order);
+	else
+		chunk_heap_info->order = 4;
+
+	chunk_heap_count++;
+
+	return 0;
+}
+RESERVEDMEM_OF_DECLARE(dmabuf_chunk_heap, "dma_heap,chunk",
+		       dmabuf_chunk_heap_area_init);
+#endif
+
+MODULE_DESCRIPTION("DMA-BUF Chunk Heap");
+MODULE_LICENSE("GPL v2");