[PATCH] decompress: xz: enable armthumb BCJ filter for Thumb-2 barebox

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

The XZ decompressor in barebox has BCJ filter support for THUMB, but
like Linux, it's unused and instead the ARM BCJ filter is used.

Fixing that lets us save a few kilobytes, which is especially useful for
legacy configuration that fit a whole barebox into limited on-chip SRAM
(and not only the prebootloader). For example, with this patch applied
barebox-am33xx-beaglebone-mlo.img is shrinked 3K from 109236 to 106028 bytes.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 lib/decompress_unxz.c | 2 ++
 scripts/xz_wrap.sh    | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/lib/decompress_unxz.c b/lib/decompress_unxz.c
index 132ab4a239b3..ad6a5f20ba28 100644
--- a/lib/decompress_unxz.c
+++ b/lib/decompress_unxz.c
@@ -133,6 +133,8 @@
 #ifdef CONFIG_ARM
 #	ifdef CONFIG_CPU_64
 #		define XZ_DEC_ARM64
+#	elif defined CONFIG_THUMB2_BAREBOX
+#		define XZ_DEC_ARMTHUMB
 #	else
 #		define XZ_DEC_ARM
 #	endif
diff --git a/scripts/xz_wrap.sh b/scripts/xz_wrap.sh
index 5b5f3adcff6d..a6373a748168 100755
--- a/scripts/xz_wrap.sh
+++ b/scripts/xz_wrap.sh
@@ -20,6 +20,10 @@ case $SRCARCH in
 	sparc)          BCJ=--sparc ;;
 esac
 
+if grep -q '^CONFIG_THUMB2_BAREBOX=y$' include/config/auto.conf; then
+	BCJ=--armthumb
+fi
+
 # clear BCJ filter if unsupported
 xz -H | grep -q -- $BCJ || BCJ=
 
-- 
2.39.2