Merge tag 'dma-mapping-6.19-2026-01-30' of git://git.kernel.org/pub/scm/linux/kernel/git/mszyprowski/linux

Pull dma-mapping fixes from Marek Szyprowski:

- important fix for ARM 32-bit based systems using cma= kernel
parameter (Oreoluwa Babatunde)

- a fix for the corner case of the DMA atomic pool based allocations
(Sai Sree Kartheek Adivi)

* tag 'dma-mapping-6.19-2026-01-30' of git://git.kernel.org/pub/scm/linux/kernel/git/mszyprowski/linux:
dma/pool: distinguish between missing and exhausted atomic pools
of: reserved_mem: Allow reserved_mem framework detect "cma=" kernel param

drivers/of/of_reserved_mem.c

···
 	phys_addr_t base, size;
 	int i, len;
 	const __be32 *prop;
-	bool nomap;
+	bool nomap, default_cma;
 
 	prop = of_flat_dt_get_addr_size_prop(node, "reg", &len);
 	if (!prop)
 		return -ENOENT;
 
 	nomap = of_get_flat_dt_prop(node, "no-map", NULL) != NULL;
+	default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL);
+
+	if (default_cma && cma_skip_dt_default_reserved_mem()) {
+		pr_err("Skipping dt linux,cma-default for \"cma=\" kernel param.\n");
+		return -EINVAL;
+	}
 
 	for (i = 0; i < len; i++) {
 		u64 b, s;
···
 
 	fdt_for_each_subnode(child, fdt, node) {
 		const char *uname;
+		bool default_cma = of_get_flat_dt_prop(child, "linux,cma-default", NULL);
 		u64 b, s;
 
 		if (!of_fdt_device_is_available(fdt, child))
+			continue;
+		if (default_cma && cma_skip_dt_default_reserved_mem())
 			continue;
 
 		if (!of_flat_dt_get_addr_size(child, "reg", &b, &s))
···
 	phys_addr_t base = 0, align = 0, size;
 	int i, len;
 	const __be32 *prop;
-	bool nomap;
+	bool nomap, default_cma;
 	int ret;
 
 	prop = of_get_flat_dt_prop(node, "size", &len);
···
 	}
 
 	nomap = of_get_flat_dt_prop(node, "no-map", NULL) != NULL;
+	default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL);
+
+	if (default_cma && cma_skip_dt_default_reserved_mem()) {
+		pr_err("Skipping dt linux,cma-default for \"cma=\" kernel param.\n");
+		return -EINVAL;
+	}
 
 	/* Need adjust the alignment to satisfy the CMA requirement */
 	if (IS_ENABLED(CONFIG_CMA)

include/linux/cma.h

···
 
 extern void cma_reserve_pages_on_error(struct cma *cma);
 
+#ifdef CONFIG_DMA_CMA
+extern bool cma_skip_dt_default_reserved_mem(void);
+#else
+static inline bool cma_skip_dt_default_reserved_mem(void)
+{
+	return false;
+}
+#endif
+
 #ifdef CONFIG_CMA
 struct folio *cma_alloc_folio(struct cma *cma, int order, gfp_t gfp);
 bool cma_free_folio(struct cma *cma, const struct folio *folio);

kernel/dma/contiguous.c

···
 }
 early_param("cma", early_cma);
 
+/*
+ * cma_skip_dt_default_reserved_mem - This is called from the
+ * reserved_mem framework to detect if the default cma region is being
+ * set by the "cma=" kernel parameter.
+ */
+bool __init cma_skip_dt_default_reserved_mem(void)
+{
+	return size_cmdline != -1;
+}
+
 #ifdef CONFIG_DMA_NUMA_CMA
 
 static struct cma *dma_contiguous_numa_area[MAX_NUMNODES];
···
 	bool default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL);
 	struct cma *cma;
 	int err;
-
-	if (size_cmdline != -1 && default_cma) {
-		pr_info("Reserved memory: bypass %s node, using cmdline CMA params instead\n",
-			rmem->name);
-		return -EBUSY;
-	}
 
 	if (!of_get_flat_dt_prop(node, "reusable", NULL) ||
 	    of_get_flat_dt_prop(node, "no-map", NULL))

kernel/dma/pool.c

···
 {
 	struct gen_pool *pool = NULL;
 	struct page *page;
+	bool pool_found = false;
 
 	while ((pool = dma_guess_pool(pool, gfp))) {
+		pool_found = true;
 		page = __dma_alloc_from_pool(dev, size, pool, cpu_addr,
 					     phys_addr_ok);
 		if (page)
 			return page;
 	}
 
-	WARN(1, "Failed to get suitable pool for %s\n", dev_name(dev));
+	if (pool_found)
+		WARN(!(gfp & __GFP_NOWARN), "DMA pool exhausted for %s\n", dev_name(dev));
+	else
+		WARN(1, "Failed to get suitable pool for %s\n", dev_name(dev));
 	return NULL;
 }