diff --git a/lib/functions/compilation/uboot-git.sh b/lib/functions/compilation/uboot-git.sh
new file mode 100644
index 000000000..ea6f1fe71
--- /dev/null
+++ b/lib/functions/compilation/uboot-git.sh
@@ -0,0 +1,40 @@
+function uboot_prepare_bare_repo() {
+	uboot_git_bare_tree="${SRC}/cache/git-bare/u-boot" # sets the outer scope variable
+	declare uboot_git_bare_tree_done_marker="${uboot_git_bare_tree}/.git/armbian-bare-tree-done"
+
+	if [[ ! -d "${uboot_git_bare_tree}" || ! -f "${uboot_git_bare_tree_done_marker}" ]]; then
+		if [[ -d "${uboot_git_bare_tree}" ]]; then
+			display_alert "Removing old u-boot bare tree" "${uboot_git_bare_tree}" "info"
+			rm -rf "${uboot_git_bare_tree}"
+		fi
+
+		# get the mainline u-boot repo completely; use clone, not fetch.
+		display_alert "Cloning u-boot from mainline into bare tree" "this might take a somewhat-long time" "info"
+		declare -a verbose_params=() && if_user_on_terminal_and_not_logging_add verbose_params "--verbose" "--progress"
+		run_host_command_logged git clone "${verbose_params[@]}" --tags --no-checkout \
+			"${MAINLINE_UBOOT_SOURCE}" "${uboot_git_bare_tree}"
+
+		# write the marker file
+		touch "${uboot_git_bare_tree_done_marker}"
+	fi
+
+	return 0
+}
+
+function uboot_prepare_git() {
+	display_alert "Preparing git for u-boot" "BOOTSOURCE: ${BOOTSOURCE}" "debug"
+	if [[ -n $BOOTSOURCE ]] && [[ "${BOOTSOURCE}" != "none" ]]; then
+		# Prepare the git bare repo for u-boot.
+		declare uboot_git_bare_tree
+		uboot_prepare_bare_repo # this sets uboot_git_bare_tree
+
+		display_alert "Downloading sources" "u-boot; BOOTSOURCEDIR=${BOOTSOURCEDIR}" "git"
+
+		GIT_FIXED_WORKDIR="${BOOTSOURCEDIR}" \
+			GIT_BARE_REPO_FOR_WORKTREE="${uboot_git_bare_tree}" \
+			GIT_BARE_REPO_INITIAL_BRANCH="master" \
+			GIT_SKIP_SUBMODULES="${UBOOT_GIT_SKIP_SUBMODULES}" \
+			fetch_from_repo "$BOOTSOURCE" "$BOOTDIR" "$BOOTBRANCH" "yes" # fetch_from_repo <url> <dir> <ref> <subdir_flag>
+	fi
+	return 0
+}
diff --git a/lib/functions/compilation/uboot.sh b/lib/functions/compilation/uboot.sh
index 60cc5265b..84018f68b 100644
--- a/lib/functions/compilation/uboot.sh
+++ b/lib/functions/compilation/uboot.sh
@@ -240,14 +240,11 @@ function deploy_built_uboot_bins_for_one_target_to_packaging_area() {
 function compile_uboot() {
 	display_alert "Compiling u-boot" "BOOTSOURCE: ${BOOTSOURCE}" "debug"
 	if [[ -n $BOOTSOURCE ]] && [[ "${BOOTSOURCE}" != "none" ]]; then
-		display_alert "Downloading sources" "u-boot" "git"
-		GIT_SKIP_SUBMODULES="${UBOOT_GIT_SKIP_SUBMODULES}" fetch_from_repo "$BOOTSOURCE" "$BOOTDIR" "$BOOTBRANCH" "yes" # fetch_from_repo <url> <dir> <ref> <subdir_flag>
-
 		display_alert "Extensions: fetch custom uboot" "fetch_custom_uboot" "debug"
 		call_extension_method "fetch_custom_uboot" <<- 'FETCH_CUSTOM_UBOOT'
 			*allow extensions to fetch extra uboot sources*
 			For downstream uboot et al.
-			This is done after `GIT_SKIP_SUBMODULES="${UBOOT_GIT_SKIP_SUBMODULES}" fetch_from_repo "$BOOTSOURCE" "$BOOTDIR" "$BOOTBRANCH" "yes"`
+			This is done after `fetch_from_repo`, but before actually compiling u-boot.
 		FETCH_CUSTOM_UBOOT
 	fi
 
diff --git a/lib/functions/host/mountpoints.sh b/lib/functions/host/mountpoints.sh
index b374dbca6..d4002a954 100644
--- a/lib/functions/host/mountpoints.sh
+++ b/lib/functions/host/mountpoints.sh
@@ -14,6 +14,7 @@ function prepare_armbian_mountpoints_description_dict() {
 		"cache/initrd"
 		"cache/sources"
 		"cache/sources/linux-kernel-worktree"
+		"cache/sources/u-boot-worktree"
 		"cache/ccache"
 	)
 
@@ -32,6 +33,7 @@ function prepare_armbian_mountpoints_description_dict() {
 		["cache/initrd"]="docker_kind_linux=bind docker_kind_darwin=namedvolume"                        # initrd.img cache, can be bind-mounted or a volume. On Darwin it's too slow to bind-mount, so it's a volume by default. On Linux, it's a bind-mount by default.
 		["cache/sources"]="docker_kind_linux=bind docker_kind_darwin=namedvolume"                       # operating directory. many things are cloned in here, and some are even built inside. needs to be local to the container, so it's a volume by default. On Linux, it's a bind-mount by default.
 		["cache/sources/linux-kernel-worktree"]="docker_kind_linux=bind docker_kind_darwin=namedvolume" # working tree for kernel builds. huge. contains both sources and the built object files. needs to be local to the container, so it's a volume by default. On Linux, it's a bind-mount by default.
+		["cache/sources/u-boot-worktree"]="docker_kind_linux=bind docker_kind_darwin=namedvolume"       # working tree for u-boot. large. contains both sources and the built object files. needs to be local to the container, so it's a volume by default. On Linux, it's a bind-mount by default.
 		["cache/ccache"]="docker_kind_linux=bind docker_kind_darwin=namedvolume"                        # ccache object store. limited to 5gb by default. needs to be local to the container, so it's a volume by default. On Linux, it's a bind-mount by default.
 	)
 
@@ -41,6 +43,7 @@ function prepare_armbian_mountpoints_description_dict() {
 		"cache/gitballs"
 		"cache/sources/kernel"
 		"cache/sources/linux-kernel"
+		"cache/sources/u-boot"
 	)
 }
 
diff --git a/lib/functions/main/config-prepare.sh b/lib/functions/main/config-prepare.sh
index 10f481bf6..075cb5285 100644
--- a/lib/functions/main/config-prepare.sh
+++ b/lib/functions/main/config-prepare.sh
@@ -114,7 +114,7 @@ function prepare_and_config_main_build_single() {
 		IMAGE_TYPE=user-built
 	fi
 
-	export BOOTSOURCEDIR="${BOOTDIR}/$(branch2dir "${BOOTBRANCH}")"
+	export BOOTSOURCEDIR="u-boot-worktree/${BOOTDIR}/$(branch2dir "${BOOTBRANCH}")"
 	[[ -n $ATFSOURCE ]] && export ATFSOURCEDIR="${ATFDIR}/$(branch2dir "${ATFBRANCH}")"
 
 	export BSP_CLI_PACKAGE_NAME="armbian-bsp-cli-${BOARD}${EXTRA_BSP_NAME}"
diff --git a/lib/functions/main/default-build.sh b/lib/functions/main/default-build.sh
index 5138c3599..1df843a5c 100644
--- a/lib/functions/main/default-build.sh
+++ b/lib/functions/main/default-build.sh
@@ -92,6 +92,7 @@ function main_default_build_single() {
 				fi
 				# @TODO: refactor this construct. we use it too many times.
 				if [[ "${REPOSITORY_INSTALL}" != *u-boot* ]]; then
+					LOG_SECTION="uboot_prepare_git" do_with_logging_unless_user_terminal uboot_prepare_git
 					LOG_SECTION="compile_uboot" do_with_logging compile_uboot
 				fi
 			fi
diff --git a/lib/library-functions.sh b/lib/library-functions.sh
index 82ac927ba..0d67bb58e 100644
--- a/lib/library-functions.sh
+++ b/lib/library-functions.sh
@@ -235,6 +235,15 @@ set -o errexit  ## set -e : exit the script if any statement returns a non-true
 # shellcheck source=lib/functions/compilation/patch/patching.sh
 source "${SRC}"/lib/functions/compilation/patch/patching.sh
 
+# no errors tolerated. invoked before each sourced file to make sure.
+#set -o pipefail  # trace ERR through pipes - will be enabled "soon"
+#set -o nounset   ## set -u : exit the script if you try to use an uninitialised variable - one day will be enabled
+set -o errtrace # trace ERR through - enabled
+set -o errexit  ## set -e : exit the script if any statement returns a non-true return value - enabled
+### lib/functions/compilation/uboot-git.sh
+# shellcheck source=lib/functions/compilation/uboot-git.sh
+source "${SRC}"/lib/functions/compilation/uboot-git.sh
+
 # no errors tolerated. invoked before each sourced file to make sure.
 #set -o pipefail  # trace ERR through pipes - will be enabled "soon"
 #set -o nounset   ## set -u : exit the script if you try to use an uninitialised variable - one day will be enabled