fit: prefer the default configuration on best-match ties

With CONFIG_FIT_BEST_MATCH, fit_conf_find_compat() selects the
configuration matching the most specific U-Boot compatible string; on
equal matches the first listed configuration wins and the configurations
node 'default' property is never consulted.

A FIT whose configurations all share the same base devicetree compatible
(e.g. one manifest carrying a base tree plus overlay combinations for a
single board) therefore always boots the first configuration, silently
ignoring the default chosen by the manifest author.

Break score ties in favour of the default configuration. A strictly
better compatible match still wins over it, and FITs without a default
keep the current first-listed behaviour.

Reviewed-by: Simon Glass <[email protected]>
Reviewed-by: Tom Rini <[email protected]>
Signed-off-by: Carlo Caione <[email protected]>

1 files changed, 6 insertions, 0 deletions

diff --git a/doc/usage/fit/overlay-fdt-boot.rst b/doc/usage/fit/overlay-fdt-boot.rst
index 5df304047c6..e210619a26d 100644
--- a/doc/usage/fit/overlay-fdt-boot.rst
+++ b/doc/usage/fit/overlay-fdt-boot.rst
@@ -111,6 +111,12 @@ Where config is one of::
 
 This selects the DTB to use when booting.
 
+If no configuration is given, U-Boot picks one automatically: with
+``CONFIG_FIT_BEST_MATCH`` it selects the configuration whose fdt is the most
+compatible with U-Boot's own control devicetree, and falls back to the
+``default`` configuration otherwise. When several configurations match
+equally well, the ``default`` one is preferred.
+
 .. _fit_configuration_using_overlays:
 
 Configuration using overlays