Create the logic to store coherent reserved memory regions
within the coherent DMA code; and provide an iterator
(i.e., dma_coherent_get_reserved_region()) to allow
consumers of this API retrieving the regions.

Note: since the consumer of this iterator is going
to be the specific coherent memory dmabuf heap module, this
commit introduces a check for CONFIG_DMABUF_HEAPS_COHERENT,
which is defined in the subsequent patch, to maintain a
clean split between the kernel code and the heap
module code.

Signed-off-by: Albert Esteve <aesteve@redhat.com>
---
 include/linux/dma-map-ops.h |  7 +++++++
 kernel/dma/coherent.c       | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 60b63756df821..c87e5e44e5383 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -12,6 +12,7 @@
 
 struct cma;
 struct iommu_ops;
+struct reserved_mem;
 
 struct dma_map_ops {
 	void *(*alloc)(struct device *dev, size_t size,
@@ -161,6 +162,7 @@ int dma_alloc_from_dev_coherent(struct device *dev, ssize_t size,
 int dma_release_from_dev_coherent(struct device *dev, int order, void *vaddr);
 int dma_mmap_from_dev_coherent(struct device *dev, struct vm_area_struct *vma,
 		void *cpu_addr, size_t size, int *ret);
+struct reserved_mem *dma_coherent_get_reserved_region(unsigned int idx);
 #else
 static inline int dma_declare_coherent_memory(struct device *dev,
 		phys_addr_t phys_addr, dma_addr_t device_addr, size_t size)
@@ -172,6 +174,11 @@ static inline int dma_declare_coherent_memory(struct device *dev,
 #define dma_release_from_dev_coherent(dev, order, vaddr) (0)
 #define dma_mmap_from_dev_coherent(dev, vma, vaddr, order, ret) (0)
 static inline void dma_release_coherent_memory(struct device *dev) { }
+static inline
+struct reserved_mem *dma_coherent_get_reserved_region(unsigned int idx)
+{
+	return NULL;
+}
 #endif /* CONFIG_DMA_DECLARE_COHERENT */
 
 #ifdef CONFIG_DMA_GLOBAL_POOL
diff --git a/kernel/dma/coherent.c b/kernel/dma/coherent.c
index 1147497bc512c..d0d0979ffb153 100644
--- a/kernel/dma/coherent.c
+++ b/kernel/dma/coherent.c
@@ -9,6 +9,7 @@
 #include <linux/module.h>
 #include <linux/dma-direct.h>
 #include <linux/dma-map-ops.h>
+#include <linux/dma-heap.h>
 
 struct dma_coherent_mem {
 	void		*virt_base;
@@ -334,6 +335,31 @@ static phys_addr_t dma_reserved_default_memory_base __initdata;
 static phys_addr_t dma_reserved_default_memory_size __initdata;
 #endif
 
+#define MAX_COHERENT_REGIONS 64
+
+static struct reserved_mem *rmem_coherent_areas[MAX_COHERENT_REGIONS];
+static unsigned int rmem_coherent_areas_num;
+
+static int rmem_coherent_insert_area(struct reserved_mem *rmem)
+{
+	if (rmem_coherent_areas_num >= MAX_COHERENT_REGIONS) {
+		pr_warn("Deferred heap areas list full, dropping %s\n",
+			rmem->name ? rmem->name : "unknown");
+		return -EINVAL;
+	}
+	rmem_coherent_areas[rmem_coherent_areas_num++] = rmem;
+	return 0;
+}
+
+struct reserved_mem *dma_coherent_get_reserved_region(unsigned int idx)
+{
+	if (idx >= rmem_coherent_areas_num)
+		return NULL;
+
+	return rmem_coherent_areas[idx];
+}
+EXPORT_SYMBOL_GPL(dma_coherent_get_reserved_region);
+
 static int rmem_dma_device_init(struct reserved_mem *rmem, struct device *dev)
 {
 	struct dma_coherent_mem *mem = rmem->priv;
@@ -393,6 +419,14 @@ static int __init rmem_dma_setup(struct reserved_mem *rmem)
 	rmem->ops = &rmem_dma_ops;
 	pr_info("Reserved memory: created DMA memory pool at %pa, size %ld MiB\n",
 		&rmem->base, (unsigned long)rmem->size / SZ_1M);
+
+	if (IS_ENABLED(CONFIG_DMABUF_HEAPS_COHERENT)) {
+		int ret = rmem_coherent_insert_area(rmem);
+
+		if (ret)
+			pr_warn("Reserved memory: failed to store coherent area for %s (%d)\n",
+				rmem->name ? rmem->name : "unknown", ret);
+	}
 	return 0;
 }
 

-- 
2.52.0