linux-kernel - Re: [PATCH 4/4] microblaze: remove unnecessary system.dts

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Message-ID: <b211188e-6c31-49fd-96be-137d3fc3f7bb@monstr.eu>
Date: Mon, 3 Feb 2025 12:17:16 +0100
From: Michal Simek <monstr@...str.eu>
To: Masahiro Yamada <masahiroy@...nel.org>, Rob Herring <robh@...nel.org>,
 "Simek, Michal" <michal.simek@....com>
Cc: linux-kernel@...r.kernel.org, Conor Dooley <conor+dt@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH 4/4] microblaze: remove unnecessary system.dts



On 2/1/25 04:42, Masahiro Yamada wrote:
> On Sat, Feb 1, 2025 at 7:25 AM Rob Herring <robh@...nel.org> wrote:
>>
>> On Tue, Jan 14, 2025 at 12:15 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>>>
>>> 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/
>>>
>>> Signed-off-by: Masahiro Yamada <masahiroy@...nel.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
> 

I have played with this and pretty much this patch is blocking 
simpleImage.system build target.

I have no issue with patches 1-3 and I would keep system.dts as empty and keep 
it in the tree because users (including me) just rewrite system.dts with proper 
DTS and call make simpleImage.system.

Thanks,
Michal

-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Xilinx Microblaze
Maintainer of Linux kernel - Xilinx Zynq ARM and ZynqMP/Versal ARM64 SoCs
U-Boot custodian - Xilinx Microblaze/Zynq/ZynqMP/Versal/Versal NET SoCs
TF-A maintainer - Xilinx ZynqMP/Versal/Versal NET SoCs