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

[Michal Simek]

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