Re: [PATCH 2/3] dma-buf: heaps: add chunk heap to dmabuf heaps

This patch adds support for a chunk heap that allows for buffers
that are made up of a list of fixed size chunks taken from a CMA.
Chunk sizes are configuratd when the heaps are created.

Signed-off-by: Hyesoo Yu <redacted>
---
 drivers/dma-buf/heaps/Kconfig      |   9 ++
 drivers/dma-buf/heaps/Makefile     |   1 +
 drivers/dma-buf/heaps/chunk_heap.c | 222 +++++++++++++++++++++++++++++++++++++
 3 files changed, 232 insertions(+)
 create mode 100644 drivers/dma-buf/heaps/chunk_heap.c

diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
index a5eef06..98552fa 100644
--- a/drivers/dma-buf/heaps/Kconfig
+++ b/drivers/dma-buf/heaps/Kconfig

@@ -12,3 +12,12 @@ 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
+	tristate "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 allocate the buffers that
+	  are made up to a list of fixed size chunks tasken from CMA. Chunk sizes
+	  are configurated when the heaps are created.

diff --git a/drivers/dma-buf/heaps/Makefile b/drivers/dma-buf/heaps/Makefile
index 6e54cde..3b2a0986 100644
--- a/drivers/dma-buf/heaps/Makefile
+++ b/drivers/dma-buf/heaps/Makefile

@@ -2,3 +2,4 @@
 obj-y					+= heap-helpers.o
 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 0000000..1eefaec
--- /dev/null
+++ b/drivers/dma-buf/heaps/chunk_heap.c

@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ION Memory Allocator chunk heap exporter
+ *
+ * Copyright (c) 2020 Samsung Electronics Co., Ltd.
+ * Author: <hyesoo.yu@samsung.com> for Samsung Electronics.
+ */
+
+#include <linux/platform_device.h>
+#include <linux/cma.h>
+#include <linux/device.h>
+#include <linux/dma-buf.h>
+#include <linux/dma-heap.h>
+#include <linux/dma-contiguous.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/highmem.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/scatterlist.h>
+#include <linux/sched/signal.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/of.h>
+
+#include "heap-helpers.h"
+
+struct chunk_heap {
+	struct dma_heap *heap;
+	phys_addr_t base;
+	phys_addr_t size;
+	atomic_t cur_pageblock_idx;
+	unsigned int max_num_pageblocks;
+	unsigned int order;
+};
+
+static void chunk_heap_free(struct heap_helper_buffer *buffer)
+{
+	struct chunk_heap *chunk_heap = dma_heap_get_drvdata(buffer->heap);
+	pgoff_t pg;
+
+	for (pg = 0; pg < buffer->pagecount; pg++)
+		__free_pages(buffer->pages[pg], chunk_heap->order);
+	kvfree(buffer->pages);
+	kfree(buffer);
+}
+
+static inline unsigned long chunk_get_next_pfn(struct chunk_heap *chunk_heap)
+{
+	unsigned long i = atomic_inc_return(&chunk_heap->cur_pageblock_idx) %
+		chunk_heap->max_num_pageblocks;
+
+	return PHYS_PFN(chunk_heap->base) + i * pageblock_nr_pages;
+}
+
+static int chunk_alloc_pages(struct chunk_heap *chunk_heap, struct page **pages,
+			     unsigned int order, unsigned int count)
+{
+	unsigned long base;
+	unsigned int i = 0, nr_block = 0, nr_elem, ret;
+
+	while (count) {
+		/*
+		 * If the number of scanned page block is the same as max block,
+		 * the tries of allocation fails.
+		 */
+		if (nr_block++ == chunk_heap->max_num_pageblocks) {
+			ret = -ENOMEM;
+			goto err_bulk;
+		}
+		base = chunk_get_next_pfn(chunk_heap);
+		nr_elem = min_t(unsigned int, count, pageblock_nr_pages >> order);
+		ret = alloc_pages_bulk(base, base + pageblock_nr_pages, MIGRATE_CMA,
+				       GFP_KERNEL, order, nr_elem, pages + i);