mm/cma: support to set CMA area status

Add an optional empty property - 'inactive' for reserved memory,
only do effect for regions with reusable property.

CMA area in 'inactive' status means that the operating system can't
alloc pages from the regions.

Change-Id: I34ecde9bc9c2e3cec175e6c032911c1bae21295c
Signed-off-by: Jianqun Xu <jay.xu@rock-chips.com>

include/linux/cma.h

@@ -37,4 +37,7 @@ extern struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 extern bool cma_release(struct cma *cma, const struct page *pages, unsigned int count);
 
 extern int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data);
+
+extern void set_cma_area_inactive(struct cma *cma);
+
 #endif

kernel/dma/contiguous.c

@@ -270,6 +270,9 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem)
 	if (of_get_flat_dt_prop(node, "linux,cma-default", NULL))
 		dma_contiguous_set_default(cma);
 
+	if (of_get_flat_dt_prop(node, "inactive", NULL))
+		set_cma_area_inactive(cma);
+
 	rmem->ops = &rmem_cma_ops;
 	rmem->priv = cma;
 

mm/cma.c

@@ -112,6 +112,9 @@ static int __init cma_activate_area(struct cma *cma)
 		return -ENOMEM;
 	}
 
+	if (cma->inactive)
+		goto done;
+
 	WARN_ON_ONCE(!pfn_valid(pfn));
 	zone = page_zone(pfn_to_page(pfn));
 
@@ -133,6 +136,7 @@ static int __init cma_activate_area(struct cma *cma)
 		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
 	} while (--i);
 
+done:
 	mutex_init(&cma->lock);
 
 #ifdef CONFIG_CMA_DEBUGFS
@@ -467,6 +471,11 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 		mutex_unlock(&cma->lock);
 
 		pfn = cma->base_pfn + (bitmap_no << cma->order_per_bit);
+		if (cma->inactive) {
+			ret = 0;
+			page = pfn_to_page(pfn);
+			break;
+		}
 		mutex_lock(&cma_mutex);
 		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA,
 				     GFP_KERNEL | (no_warn ? __GFP_NOWARN : 0));
@@ -535,7 +544,8 @@ bool cma_release(struct cma *cma, const struct page *pages, unsigned int count)
 
 	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
 
-	free_contig_range(pfn, count);
+	if (!cma->inactive)
+		free_contig_range(pfn, count);
 	cma_clear_bitmap(cma, pfn, count);
 	trace_cma_release(pfn, pages, count);
 
@@ -557,3 +567,9 @@ int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(cma_for_each_area);
+
+void set_cma_area_inactive(struct cma *cma)
+{
+	cma->inactive = true;
+}
+EXPORT_SYMBOL_GPL(set_cma_area_inactive);

mm/cma.h

@@ -13,6 +13,7 @@ struct cma {
 	spinlock_t mem_head_lock;
 #endif
 	const char *name;
+	bool inactive;
 };
 
 extern struct cma cma_areas[MAX_CMA_AREAS];