[PATCH] imx8m: soc: cope with existing optee node

[Vincent Stehlé]

On i.MX8M SoCs, the /firmware/optee Devicetree node is created just before
booting the OS when OP-TEE is found running. If the node already exists,
this results in an error, which prevents the OS to boot:

  Could not create optee node.
  ERROR: system-specific fdt fixup failed: FDT_ERR_EXISTS
   - must RESET the board to recover.

  failed to process device tree

On the i.MX8M systems where CONFIG_OF_SYSTEM_SETUP is defined, the
ft_add_optee_node() function is called before booting the OS. It will
create the OP-TEE Devicetree node and populate it with reserved memory
informations gathered at runtime.

On on most i.MX8M systems the Devicetree is built with an optee node if
CONFIG_OPTEE is defined. This node is indeed necessary for commands and
drivers communicating with OP-TEE, even before attempting OS boot.

The aforementioned issue can happen on the Compulab IOT-GATE-iMX8, which is
the only in-tree i.MX8M system where both CONFIG_OPTEE and
CONFIG_OF_SYSTEM_SETUP are defined (see the imx8mm-cl-iot-gate*
defconfigs).

Deal with an existing optee node gracefully at runtime to fix this issue.

Signed-off-by: Vincent Stehlé <vincent.stehle at arm.com>
Cc: Stefano Babic <sbabic at denx.de>
Cc: Fabio Estevam <festevam at gmail.com>
Cc: Tom Rini <trini at konsulko.com>
Cc: Tim Harvey <tharvey at gateworks.com>
---
 arch/arm/mach-imx/imx8m/soc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-imx/imx8m/soc.c b/arch/arm/mach-imx/imx8m/soc.c
index 85dc8b51a14..567e8e9e81a 100644
--- a/arch/arm/mach-imx/imx8m/soc.c
+++ b/arch/arm/mach-imx/imx8m/soc.c
@@ -1270,8 +1270,9 @@ static int ft_add_optee_node(void *fdt, struct bd_info *bd)
 		}
 	}
 
+	/* Locate the optee node if it exists or create it. */
 	subpath = "optee";
-	offs = fdt_add_subnode(fdt, offs, subpath);
+	offs = fdt_find_or_add_subnode(fdt, offs, subpath);
 	if (offs < 0) {
 		printf("Could not create %s node.\n", subpath);
 		return offs;
-- 
2.47.2