riscv: do not set default fdt for VisionFive 2

Currently in set_fdtfile() we set the value of environment variable fdtfile
unconditionally. The implies that a value in the environment will be
ignored.

With the patch environment variable fdtfile will only be set if it does not
yet exist. This requires that CONFIG_DEFAULT_FDT_FILE is not set.

Now the user can either set and save fdtfile interactively or in the U-Boot
configuration to overrule the device-tree name chosen based on the
hardware in set_fdtfile().

Reported-by: E Shattow <[email protected]>
Signed-off-by: Heinrich Schuchardt <[email protected]>
Reviewed-by: Leo Yu-Chi Liang <[email protected]>

1 files changed, 18 insertions, 0 deletions

diff --git a/doc/board/starfive/visionfive2.rst b/doc/board/starfive/visionfive2.rst
index abda8ac21bc..2c68df3ce4d 100644
--- a/doc/board/starfive/visionfive2.rst
+++ b/doc/board/starfive/visionfive2.rst
@@ -71,6 +71,24 @@ Now build the U-Boot SPL and U-Boot proper
 This will generate the U-Boot SPL image (spl/u-boot-spl.bin.normal.out) as well
 as the FIT image (u-boot.itb) with OpenSBI and U-Boot.
 
+Device-tree selection
+~~~~~~~~~~~~~~~~~~~~~
+
+Depending on the board version U-Boot set variable $fdtfile to either
+starfive/jh7110-starfive-visionfive-2-v1.2a.dtb or
+starfive/jh7110-starfive-visionfive-2-v1.3b.dtb.
+
+To overrule this selection the variable can be set manually and saved in the
+environment
+
+::
+
+    setenv fdtfile my_device-tree.dtb
+    env save
+
+or the configuration variable CONFIG_DEFAULT_FDT_FILE can be used to provide
+a default value.
+
 Flashing
 ~~~~~~~~