[PATCH v4 2/4] remoteproc: imx_rpoc: use memory-region-names to avoid hidden ABI

[Frank . Li]

From: Laurentiu Mihalcea <laurentiu.mihalcea@xxxxxxx>

The driver currently derives the memory region type from the referenced
memory node name, creating a hidden DT ABI. Since memory node names are
not constrained by the binding, incorrect names can silently pass DT
validation, as seen in examples using "vdevbuffer" instead of
"vdev0buffer" ([1] and [2]).

Parse memory-region-names to identify the expected memory regions and avoid
relying on memory node names as ABI.

Link: https://lore.kernel.org/imx/a3602ef8-2b77-4cc3-adef-2c4cba08a5d9@xxxxxxxxxxxx/ [1]
Link: https://lore.kernel.org/imx/alexXTYQHUs76J7v@SMW015318/T/#mb9dc709ff3adc24d9db6d30c973f37b580f6f1f9 [2]

Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@xxxxxxx>
Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
---
 drivers/remoteproc/imx_rproc.c | 13 +++++++++++--
 drivers/remoteproc/imx_rproc.h | 21 +++++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/remoteproc/imx_rproc.c b/drivers/remoteproc/imx_rproc.c
index 745ce52cd8226..ce9bdfc1fa985 100644
--- a/drivers/remoteproc/imx_rproc.c
+++ b/drivers/remoteproc/imx_rproc.c
@@ -643,7 +643,7 @@ static int imx_rproc_prepare(struct rproc *rproc)
 		int err;
 		struct resource res;
 
-		err = of_reserved_mem_region_to_resource(np, i++, &res);
+		err = imx_rproc_rmem_to_resource(np, i++, &res);
 		if (err)
 			break;
 
@@ -818,11 +818,20 @@ static int imx_rproc_addr_init(struct imx_rproc *priv,
 	if (nph <= 0)
 		return 0;
 
+	if (!of_property_present(np, "memory-region-names")) {
+		dev_warn(dev, "using node names for carveouts should be avoided\n");
+	} else {
+		if (nph != of_property_count_strings(np, "memory-region-names")) {
+			dev_err(dev, "invalid reserved memory name count\n");
+			return -EINVAL;
+		}
+	}
+
 	/* remap optional addresses */
 	for (a = 0; a < nph; a++) {
 		struct resource res;
 
-		err = of_reserved_mem_region_to_resource(np, a, &res);
+		err = imx_rproc_rmem_to_resource(np, a, &res);
 		if (err) {
 			dev_err(dev, "unable to resolve memory region\n");
 			return err;
diff --git a/drivers/remoteproc/imx_rproc.h b/drivers/remoteproc/imx_rproc.h
index 0d7d48352a109..3632bc375c711 100644
--- a/drivers/remoteproc/imx_rproc.h
+++ b/drivers/remoteproc/imx_rproc.h
@@ -7,6 +7,8 @@
 #ifndef _IMX_RPROC_H
 #define _IMX_RPROC_H
 
+#include <linux/of_reserved_mem.h>
+
 /* address translation table */
 struct imx_rproc_att {
 	u32 da;	/* device address (From Cortex M4 view)*/
@@ -45,4 +47,23 @@ struct imx_rproc_dcfg {
 	u32				reset_vector_mask;
 };
 
+static inline int imx_rproc_rmem_to_resource(struct device_node *np,
+					     int index,
+					     struct resource *res)
+{
+	int ret;
+
+	ret = of_reserved_mem_region_to_resource(np, index, res);
+	if (ret)
+		return ret;
+
+	/* "memory-region-names" is optional */
+	ret = of_property_read_string_index(np, "memory-region-names",
+					    index, &res->name);
+	if (ret == -EINVAL)
+		return 0;
+
+	return ret;
+}
+
 #endif /* _IMX_RPROC_H */

-- 
2.43.0