On Sat, Feb 1, 2025 at 7:25 AM Rob Herring [off-list ref] wrote:

On Tue, Jan 14, 2025 at 12:15 PM Masahiro Yamada [off-list ref] wrote:

quoted

The default image linux.bin does not contain any DTB, but a separate
system.dtb is compiled.

Michal Simek clearly explained "system.dtb is really old dtb more for
demonstration purpose and nothing else and likely it is not working on
any existing board." [1]

The system.dts is not necessary even for demonstration purposes. There
is no need to compile out-of-tree *.dts under arch/microblaze/boot/dts/
unless it is embedded into the kernel. Users can directly use dtc.

[1]: https://lore.kernel.org/all/d2bdfbfd-3721-407f-991e-566d48392add@amd.com/ (local)

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 arch/microblaze/boot/dts/Makefile   |   3 +-
 arch/microblaze/boot/dts/system.dts | 353 ----------------------------
 2 files changed, 1 insertion(+), 355 deletions(-)
 delete mode 100644 arch/microblaze/boot/dts/system.dts

diff --git a/arch/microblaze/boot/dts/Makefile b/arch/microblaze/boot/dts/Makefile
index 932dc7550a1b..fa0a6c0854ca 100644
--- a/arch/microblaze/boot/dts/Makefile
+++ b/arch/microblaze/boot/dts/Makefile

@@ -1,8 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 #

-dtb-y := system.dtb
-
 ifneq ($(DTB),)
 obj-y += linked_dtb.o

@@ -11,6 +9,7 @@ $(obj)/linked_dtb.o: $(obj)/system.dtb

 # Generate system.dtb from $(DTB).dtb
 ifneq ($(DTB),system)

Can't this be dropped as setting DTB=system.dtb should work if there's
not an in-tree system.dts anymore.

I believe this ifneq is necessary, just in case
a user adds system.dtb to arch/microblaze/boot/dts/.

'system.dtb' is a special name because
arch/microblaze/boot/dts/linked_dtb.S wraps it.

So, $(DTB) is copied to system.dtb, and then
it is wrapped by linked_dtb.S.

If $(DTB) is already 'system',
we cannot copy system.dtb to itself.


See the definition of cmd_copy in scripts/Makefile.lib

cmd_copy = cat $< > $@


"cat system.dtb > system.dtb"
would create an empty system.dtb

quoted

+targets += system.dtb
 $(obj)/system.dtb: $(obj)/$(DTB).dtb FORCE
        $(call if_changed,copy)
 endif

-- 
Best Regards
Masahiro Yamada