[PATCH 6.18 049/122] of: reserved_mem: Allow reserved_mem framework detect "cma=" kernel param

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oreoluwa Babatunde <oreoluwa.babatunde@oss.qualcomm.com>

[ Upstream commit 0fd17e5983337231dc655e9ca0095d2ca3f47405 ]

When initializing the default cma region, the "cma=" kernel parameter
takes priority over a DT defined linux,cma-default region. Hence, give
the reserved_mem framework the ability to detect this so that the DT
defined cma region can skip initialization accordingly.

Signed-off-by: Oreoluwa Babatunde <oreoluwa.babatunde@oss.qualcomm.com>
Tested-by: Joy Zou <joy.zou@nxp.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Fixes: 8a6e02d0c00e ("of: reserved_mem: Restructure how the reserved memory regions are processed")
Fixes: 2c223f7239f3 ("of: reserved_mem: Restructure call site for dma_contiguous_early_fixup()")
Link: https://lore.kernel.org/r/20251210002027.1171519-1-oreoluwa.babatunde@oss.qualcomm.com
[mszyprow: rebased onto v6.19-rc1, added fixes tags, added a stub for
 cma_skip_dt_default_reserved_mem() if no CONFIG_DMA_CMA is set]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/of/of_reserved_mem.c | 19 +++++++++++++++++--
 include/linux/cma.h          |  9 +++++++++
 kernel/dma/contiguous.c      | 16 ++++++++++------
 3 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index e5ea4f1e5eff7..fe111d1ea7397 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -158,7 +158,7 @@ static int __init __reserved_mem_reserve_reg(unsigned long node,
 	phys_addr_t base, size;
 	int len;
 	const __be32 *prop;
-	bool nomap;
+	bool nomap, default_cma;
 
 	prop = of_get_flat_dt_prop(node, "reg", &len);
 	if (!prop)
@@ -171,6 +171,12 @@ static int __init __reserved_mem_reserve_reg(unsigned long node,
 	}
 
 	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;
+	}
 
 	while (len >= t_len) {
 		base = dt_mem_next_cell(dt_root_addr_cells, &prop);
@@ -253,10 +259,13 @@ void __init fdt_scan_reserved_mem_reg_nodes(void)
 
 	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))
 			continue;
@@ -395,7 +404,7 @@ static int __init __reserved_mem_alloc_size(unsigned long node, const char *unam
 	phys_addr_t base = 0, align = 0, size;
 	int len;
 	const __be32 *prop;
-	bool nomap;
+	bool nomap, default_cma;
 	int ret;
 
 	prop = of_get_flat_dt_prop(node, "size", &len);
@@ -419,6 +428,12 @@ static int __init __reserved_mem_alloc_size(unsigned long node, const char *unam
 	}
 
 	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)
diff --git a/include/linux/cma.h b/include/linux/cma.h
index 62d9c1cf63265..2e6931735880b 100644
--- a/include/linux/cma.h
+++ b/include/linux/cma.h
@@ -57,6 +57,15 @@ extern bool cma_intersects(struct cma *cma, unsigned long start, unsigned long e
 
 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);
diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index d9b9dcba6ff7c..9071c08650e3a 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -90,6 +90,16 @@ static int __init early_cma(char *p)
 }
 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];
@@ -463,12 +473,6 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem)
 	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))
 		return -EINVAL;
-- 
2.51.0