core: dt: add option to generate DTB overlay at boot

When using a memory persistent across reboots for external dtb overlay
(DRAM for instance) OP-TEE will reuse the existing dtb overlay if
CFG_EXTERNAL_DTB_OVERLAY is used. This will result in a big overlay
with duplicated nodes. In order to allow having a fresh DTB overlay
at boot, add CFG_GENERATE_DTB_OVERLAY to generate the DTB overlay at
OP-TEE boot time.
Both CFG_GENERATE_DTB_OVERLAY and CFG_EXTERNAL_DTB_OVERLAY will now
consider using the dtb address provided in r2 as well as CFG_DT_ADDR
to create the overlay if not existing.

Signed-off-by: Clément Léger <clement.leger@bootlin.com>
Reviewed-by: Etienne Carriere <etienne.carriere@linaro.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>

core/arch/arm/kernel/boot.c

@@ -75,7 +75,7 @@ DECLARE_KEEP_PAGER(sem_cpu_sync);
 #ifdef CFG_DT
 struct dt_descriptor {
 	void *blob;
-#ifdef CFG_EXTERNAL_DTB_OVERLAY
+#ifdef _CFG_USE_DTB_OVERLAY
 	int frag_id;
 #endif
 };
@@ -632,7 +632,7 @@ static TEE_Result release_external_dt(void)
 }
 boot_final(release_external_dt);
 
-#ifdef CFG_EXTERNAL_DTB_OVERLAY
+#ifdef _CFG_USE_DTB_OVERLAY
 static int add_dt_overlay_fragment(struct dt_descriptor *dt, int ioffs)
 {
 	char frag[32];
@@ -656,20 +656,16 @@ static int add_dt_overlay_fragment(struct dt_descriptor *dt, int ioffs)
 static int init_dt_overlay(struct dt_descriptor *dt, int __maybe_unused dt_size)
 {
 	int fragment;
-	int ret;
 
-	ret = fdt_check_header(dt->blob);
-	if (!ret) {
-		fdt_for_each_subnode(fragment, dt->blob, 0)
-			dt->frag_id += 1;
-		return ret;
+	if (IS_ENABLED(CFG_EXTERNAL_DTB_OVERLAY)) {
+		if (!fdt_check_header(dt->blob)) {
+			fdt_for_each_subnode(fragment, dt->blob, 0)
+				dt->frag_id += 1;
+			return 0;
+		}
 	}
 
-#ifdef CFG_DT_ADDR
 	return fdt_create_empty_tree(dt->blob, dt_size);
-#else
-	return -1;
-#endif
 }
 #else
 static int add_dt_overlay_fragment(struct dt_descriptor *dt __unused, int offs)
@@ -682,7 +678,7 @@ static int init_dt_overlay(struct dt_descriptor *dt __unused,
 {
 	return 0;
 }
-#endif /* CFG_EXTERNAL_DTB_OVERLAY */
+#endif /* _CFG_USE_DTB_OVERLAY */
 
 static int add_dt_path_subnode(struct dt_descriptor *dt, const char *path,
 			       const char *subnode)
@@ -858,7 +854,7 @@ static int add_res_mem_dt_node(struct dt_descriptor *dt, const char *name,
 		offs = 0;
 	}
 
-	if (IS_ENABLED(CFG_EXTERNAL_DTB_OVERLAY)) {
+	if (IS_ENABLED(_CFG_USE_DTB_OVERLAY)) {
 		len_size = sizeof(paddr_t) / sizeof(uint32_t);
 		addr_size = sizeof(paddr_t) / sizeof(uint32_t);
 	} else {

mk/config.mk

@@ -425,14 +425,22 @@ CFG_DT ?= n
 CFG_DTB_MAX_SIZE ?= 0x10000
 
 # Device Tree Overlay support.
-# This define enables support for an OP-TEE provided DTB overlay.
-# One of two modes is supported in this case:
-# 1. Append OP-TEE nodes to an existing DTB overlay located at CFG_DT_ADDR or
-#    passed in arg2
-# 2. Generate a new DTB overlay at CFG_DT_ADDR
-# A subsequent boot stage must then merge the generated overlay DTB into a main
+# CFG_EXTERNAL_DTB_OVERLAY allows to append a DTB overlay into an existing
+# external DTB. The overlay is created when no valid DTB overlay is found.
+# CFG_GENERATE_DTB_OVERLAY allows to create a DTB overlay at external
+# DTB location.
+# External DTB location (physical address) is provided either by boot
+# argument arg2 or from CFG_DT_ADDR if defined.
+# A subsequent boot stage can then merge the generated overlay DTB into a main
 # DTB using the standard fdt_overlay_apply() method.
 CFG_EXTERNAL_DTB_OVERLAY ?= n
+CFG_GENERATE_DTB_OVERLAY ?= n
+
+ifeq (y-y,$(CFG_EXTERNAL_DTB_OVERLAY)-$(CFG_GENERATE_DTB_OVERLAY))
+$(error CFG_EXTERNAL_DTB_OVERLAY and CFG_GENERATE_DTB_OVERLAY are exclusive)
+endif
+_CFG_USE_DTB_OVERLAY := $(call cfg-one-enabled,CFG_EXTERNAL_DTB_OVERLAY \
+			  CFG_GENERATE_DTB_OVERLAY)
 
 # All embedded tests are supposed to be disabled by default, this flag
 # is used to control the default value of all other embedded tests